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Flooding and Climate Change: Everything You Need to Know

More communities—both coastal and inland—are finding themselves underwater. Extreme weather, sea level rise, and other climate change impacts are increasingly to blame.

A large wave crashes into a seawall in Winthrop, Massachusetts, a day after a nor'easter in 2018.

AP Photo/Michael Dwyer

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Floods are already the most common and among the most deadly disasters in the United States. As  global warming continues to exacerbate sea level rise and extreme weather, flood-prone areas around the country are expected to  grow by nearly half in just this century. Here’s how climate change plays a role in flooding and how we can better keep our heads above water.

Flooding facts and causes

Climate change and flooding, consequences of flooding, flood preparation and prevention, what causes a flood.

A flood, put simply, is the accumulation of water over normally dry land. It’s typically caused by the overflow of coastal or inland waters (like rivers and streams) or by an unusual accumulation of water from heavy or prolonged rains, storm surges, or sudden snowmelt. Often, the ways in which we manage our waterways (via dams, levees, and reservoirs) and the alterations we make to land also play a role in flooding. Increased urbanization, for example, adds impermeable surfaces (think roads and parking lots), altering natural drainage systems. Areas can be especially prone to flooding when  stormwater infrastructure isn’t maintained or homes are built in areas susceptible to flooding known as floodplains. More and more, flooding factors are also linked to climate change.

Major types of floods

River flooding This occurs when a river or stream overflows its natural banks and inundates normally dry land. Most common in early spring, river flooding can result from heavy rainfall, rapidly melting snow, or ice jams. According to the 2018 study "Estimates of Present and Future Flood Risk in the Conterminous United States," published in the journal Environmental Research Letters , more than 40 million U.S. residents are at risk from flooding along rivers and streams. And even a single episode can wreak havoc on a massive scale: For instance, in 2019, a slow-motion disaster of  intense spring flooding swelled the Arkansas, Mississippi, and Missouri rivers. Hundreds of miles of levees were topped or impaired, destroying homes and supersaturating cropland. According to the National Oceanic and Atmospheric Administration (NOAA), the inland flooding caused $20 billion in damage. Some of these losses stemmed from the impact to farmers who could no longer plant or transport their crops.

Coastal flooding More than  half of the U.S. population lives or works in areas susceptible to coastal flooding, which happens when winds from a coastal storm, such as a hurricane or nor’easter, push a storm surge (essentially, a wall of water) from the ocean onto land. A storm surge can produce widespread devastation, like that seen around New York and New Jersey when  Hurricane Sandy arrived during high tide .

There are also increasing numbers of shallow, nondeadly floods caused by higher sea levels. These high tide floods (also known as “nuisance” or “sunny day” floods) occur when the sea washes up and over roads and into storm drains as the daily tides roll in. In places like Miami, increased nuisance flooding is raising concerns over  climate gentrification , as wealthier residents looking to settle on higher ground are pricing out historically underserved BIPOC communities.

Flash floods These quick-rising floods are most often caused by heavy rains over a short period—usually six hours or less. Flash floods can happen anywhere, and low-lying areas with poor drainage are particularly vulnerable. Also caused by dam or levee breaks or the sudden overflow of water due to a debris or ice jam, flash floods combine the innate hazards of a flood with speed and unpredictability. That’s why they’re responsible for the greatest number of flood-related fatalities. In late 2022 and early 2023, California was hit by deadly flash floods during powerful wintertime atmospheric rivers, which may become more powerful as climate change increases the amount of moisture they can hold.

Urban flooding The term  urban flooding refers specifically to flooding that occurs when rainfall—not an overflowing body of water—overwhelms the  stormwater drainage capacity of a densely populated area. In 2021, Hurricane Ida, strengthened by warm air, shattered records across the Northeast. In New York City, the deluge made rivers of impermeable streets and subway stations. Eleven people living in basement-level apartments drowned as the floodwaters—with nowhere else to go—swiftly overwhelmed below-ground spaces.

A tractor trailer is swept off the road by floodwaters in Nebraska in 2019.

Ryan Soderlin/Omaha World-Herald via AP

The Intergovernmental Panel on Climate Change (IPCC) has found that climate change “has detectably influenced” several of the variables that contribute to floods, such as rainfall and snowmelt. In other words, while our warming world may not be the only or most direct cause of any given flood, it exacerbates many of the factors that increase flood risk. That’s why mitigating climate change—and particularly, limiting global average temperature rise to within 1.5 degrees Celsius in this century—is an important way to avert some of the worst scenarios for sea level rise and escalating flood risks. 

How does climate change lead to flooding?

These are some of the key ways that climate change increases flood risks.

Heavier precipitation A warmer atmosphere holds—and subsequently dumps—more water. As the planet has warmed by  1.9 degrees Fahrenheit since the preindustrial revolution era, the United States has also become about 4 percent wetter, according to the federal  Climate Science Special Report. The same report says that heavy precipitation events are projected to increase by 50 percent to as much as three times the historical average in just this century. This includes extreme weather like atmospheric rivers, which are air currents that become heavy with water from the tropics. Meanwhile, in regions with significant seasonal snowmelt, hotter temperatures can trigger more rain-on-snow events, with warm rains inducing faster and earlier melting— a phenomenon playing out in the western United States. 

A building and road severely damaged by flooding in Jamestown, Colorado, in 2013

Steve Zumwalt/FEMA

More-frequent hurricanes Climate change is increasing the frequency of our strongest storms, which bring greater rains, including in places not known for flooding. In August 2023, Tropical Storm Hilary—the first storm of its kind to hit the West Coast in 84 years—broke rainfall records in Idaho, Montana, Nevada, and Oregon. Hurricane Harvey, which made landfall as a Category 4 storm in 2017 and soaked Houston homes and businesses with catastrophic floods, was the nation’s wettest storm in nearly 70 years.  Researchers  estimate that Hurricane Harvey dumped as much as 38 percent more rain than it would have without climate change. Just a month after Harvey, Hurricane Maria hit Dominica, Puerto Rico, and the U.S. Virgin Islands. The storm produced the most rainfall in the area of any weather event  since 1956 and exposed the  inadequacy of U.S. policies to respond to disasters.

According to the IPCC,  future hurricanes are expected to be as much as 37 percent wetter near their centers and about 20 percent wetter as much as 60 miles away. In the Atlantic basin, an 80 percent increase in the frequency of Category 4 and 5 hurricanes (the most destructive) is expected over the next 80 years. And it’s not only the most severely rated storms that bring the greatest flood impacts; in fact, the rating system the government uses to categorize the severity of storms is based solely on wind speed, not rainfall—so even unrated storms can unleash lethal amounts of water.

That said, gustier winds can whip up greater storm surges, which are already higher because of sea level rise. It was Hurricane Katrina’s 28-foot storm surge that overwhelmed the levees around New Orleans in 2005. Winds can also increase the destructiveness of waves, causing storm surges to get bigger and penetrate further inland.

Higher seas As ocean temperatures rise and the glaciers and ice sheets melt, global sea levels are rising —and directly contributing to coastal flooding problems. According to the Fourth National Climate Assessment, our oceans are approximately seven to eight inches higher than they were in 1900. The IPCC predicts seas around the world will rise anywhere from just under one foot to more than three and a half feet above 2000 levels by century’s end. NOAA’s projections also show that, due to regional factors such as currents bringing water to coastlines, areas along the East Coast could experience seas rising 2 feet higher as early as 2050. By then, damaging coastal flooding is expected to occur 10 times as often as it does today.

In addition to amplifying storm surges, sea level rise increases high tide flooding, which, according to NOAA, has doubled in the United States over the past 30 years. For example, by 2045, Charleston, South Carolina, could see as many as  180 tidal floods per year , compared with just 11 in 2014.

More than 100 houses burned down in Breezy Point, New York, as floodwaters isolated the community from fire and rescue workers after Hurricane Sandy.

U.S. Navy photo by Chief Mass Communication Specialist Ryan J. Courtade/Released

When flooding inundates a home or community, it upends lives. It’s important to consider  flood preparation before disaster hits by doing things like signing up for alerts, packing an emergency supply kit, and researching flood insurance options.

But the impacts of flooding go far beyond our own homes. Repairing and replacing flood-damaged roads, bridges, utilities, and other public infrastructure carry enormous costs. Between 2007 and 2017, the  National Flood Insurance Program (NFIP) paid an average of $2.9 billion per year to cover flood-related losses, with individual years often costing far more. Within two months of Hurricane Ian making landfall in Florida in 2022, the NFIP had received 44,000 flood claims from property owners. These types of estimates leave out the many people who don’t have insurance, who aren’t eligible for government disaster assistance, or who have needs above what government aid will cover. 

Flooding also brings contamination and disease. Floodwaters can carry  raw sewage , leaked toxic chemicals, and runoff from  hazardous waste sites and  factory farms. They can pollute drinking water supplies and cause  eye, ear, skin, and gastrointestinal infections. When floodwaters recede, bacteria and  mold may remain , and residents may suffer from  mental health problems and lost business or wages.

As with many natural hazards, it is most often lower-income people, people experiencing homelessness, the elderly, and  communities of color who suffer the greatest harm. These populations are  least likely to have flood insurance , access to transportation during an evacuation, cash on hand, or the ability to relocate—and the structural inequities of the past and present mean they are more likely to be in harm’s way. In August 2022, flash flooding in Jackson, Mississippi, caused the city’s main water treatment plant to fail, leaving the 150,000 residents of the majority-Black city without safe water to drink, bathe in, or cook with. In the case of  Jackson and many U.S. cities with similarly outdated infrastructure , flood damage was exacerbated by existing issues, including poor oversight, lack of local resources and capacity, and other unjust racial and economic disparities.

Entirely preventing floods isn’t possible. But there are steps that can be taken to lessen their devastation, like  flood-proofing your home ,  taking personal safety precautions , and advocating the federal government to revamp its approaches to flooding, both before and after it occurs.

A neighborhood in Port Arthur, Texas, flooded by Hurricane Harvey in 2017

Staff Sgt. Daniel J. Martinez/U.S. Air National Guard

Updating FEMA's flood maps

Mitigating potential loss from future floods requires knowing where floods are most likely to occur. In the United States, this information is provided by FEMA, which produces maps of the nation’s flood zones. Its NFIP relies on these maps to assess flood risk, determine insurance rates, and establish floodplain management standards.

FEMA flood maps depict the high-, moderate-, and low-risk flood zones of communities nationwide and can be found at  FEMA’s Flood Map Service Center . High-risk areas, often referred to as floodplains, are regions with a 1 percent (1 in 100) chance of being inundated by river or stream floodwaters of a certain magnitude in any given year. (The term  100-year flood refers to this, and does not mean a flood that’s expected to occur just once every 100 years.) But even a 1 in 100 chance of flooding each year equates to about a one in five chance that a home will flood at some point over the life of a 30-year mortgage. And FEMA’s moderate- to low-risk areas aren’t entirely safe from flooding, either: Properties in these areas still account for more than 20 percent of NFIP claims.

Flood risks change as land use and other factors change. That’s why keeping flood maps up-to-date is critical. But despite a requirement that FEMA reassess its maps every five years, nearly  60 percent are out of date—some, by decades. When Hurricane Sandy hit in 2012, for example, the flooding covered an area that was  65 percent larger than the flood-vulnerable area identified by FEMA maps.

FEMA’s maps also typically fail to take into account the effects of global warming, such as sea level rise . Instead, they rely on historical data to determine future flood hazard projections. This can cause officials to designate areas as being “safe” for development today, even when they are at risk of serious floods tomorrow. In 2021, NRDC and the Association of State Floodplain Managers  jointly petitioned FEMA to update its standards to reflect the new climate reality. After all, FEMA is required under law to use the best available science in its maps and standards. Among the petition’s requests: all new or substantially improved structures must be elevated higher than the level of a 100-year flood; all new and revised NFIP floodplain maps must depict how the floodplain will change over time, especially concerning sea level rise; homeowners seeking to retrofit their homes for the new climate reality should have easier access to NFIP funding.

Among other things, FEMA’s floodplains determine how and where homes and other structures will be built, as well as who is required to purchase flood insurance. (Coverage is mandatory if you live in a floodplain and have a federally backed mortgage.) The problem is, once again, that many of FEMA’s mapped floodplains are  inaccurate . For instance, during Hurricane Harvey, nearly three-quarters of Houston’s flood-damaged buildings sat outside of FEMA’s identified high-risk area. According to one NOAA analysis: Greater rainfall has made what used to be a 100-year flood event in Houston, by FEMA’s standards, more like a 25-year event. 

Understanding your home's flood risk

Flooding is a factor in hundreds of billions of dollars of disaster-related property damage in the United States, with many homes being  repeatedly damaged . Just one inch of flooding could cost the average homeowner  $25,000 in damage . But typical homeowners’ and renters’ insurance fails to cover flooding and  less than 4 percent of homeowners have flood coverage. That means the vast majority of Americans must take out loans or pay out of pocket to repair or replace damaged items. 

Finding out if a property is flood-prone  can also be difficult . Many states have no legal requirements that a seller disclose a property’s history of flood damage to a buyer or that a landlord tell a prospective renter. While potential homebuyers should look at FEMA’s flood history maps, there’s a more low-tech option: Introduce yourself to your prospective neighbors and ask them about flooding in the area.

This Highlands, New Jersey, home was elevated prior to Hurricane Sandy and received only minor damage.

Rosanna Arias/FEMA

For residents of repeatedly flooded homes, relocation may be the best option. But a wide array of measures exist to  prevent or reduce flood damage when that’s not possible. These include keeping gutters and drains free of debris; installing a sump pump for crawl spaces and basements; adding check valves in sewer lines to keep floodwater from backing up into the drains of your home; and safeguarding equipment by elevating furnaces, water heaters, electrical systems, generators, and air-conditioning units above flood levels. More drastic retrofits might be needed in areas with regular flooding, including raising the entire structure of a house.

Boosting local resilience

Flood resiliency can come from water-smart improvements to buildings and  green infrastructure , restored wetlands and other natural barriers, updated FEMA maps that reflect new climate realities, and an  overhaul of the NFIP to help more homeowners relocate to higher ground. One promising update is President Biden’s executive action to reinstate the  Federal Flood Risk Management Standard , which includes commonsense measures such as requiring FEMA to rebuild flood-damaged public infrastructure like police stations, schools, and hospitals to be safer. (President Trump had scrapped the standard in 2017.)

According to a Pew poll, nearly 75 percent of U.S. voters support these measures. For one thing, they can save enormous amounts of money:  For every $1 invested in riverine flood mitigation, taxpayers and the federal government save $7 in recovery costs. Moreover, such measures increase the odds that millions more people will stay safe—and dry.

In addition to securing your home, you can help secure your community. Checking in on your neighbors, sharing information, and determining how you might be able to help each other in an emergency are important components of disaster preparedness.

This story was originally published on April 19, 2019, and has been updated with new information and links.

This NRDC.org story is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the story was originally published by NRDC.org and link to the original; the story cannot be edited (beyond simple things such as grammar); you can’t resell the story in any form or grant republishing rights to other outlets; you can’t republish our material wholesale or automatically—you need to select stories individually; you can’t republish the photos or graphics on our site without specific permission; you should drop us a note to let us know when you’ve used one of our stories.

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The Many Effects of Flooding

Floods can be destructive to humans and the natural environment, but they also help to drive biodiversity and are essential to the functioning of many ecosystems.

Earth Science, Climatology, Geography, Physical Geography

1931 Yangtze River Flood

In 1931, water overwhelmed the banks of the Yangtze and Huai Rivers, resulting in the Central China flood. Killing at least hundreds of thousands and potentially millions of people, it was one of the worst flooding events in recorded history. Here, people near the Yangtze River are shown.

Photograph from Adrienne Livesey, Elaine Ryder, and Irene Brien

It is hardly surprising that rivers have been an important part of human history: They provide food, freshwater, and fertile land for growing crops. While water is essential to life, it can be a destructive force too. When rivers flood, the effects can be catastrophic. Flooding is one of the most common types of natural disaster, and the results are often fatal. The Central China flood of 1931, for example, was one of the worst flooding events in recorded history. The Yangtze and Huai Rivers broke their banks, killing as many as several million people. The aftermath was devastating; deadly waterborne diseases like dysentery and cholera spread quickly, and those who survived faced the threat of starvation. The human cost of flooding can be large, but events like this have a big impact on the natural world too, and the effects are not always negative. In fact, some ecosystems rely on seasonal flooding to drive ecological processes. Floods Can Harm Wildlife Flooding can have a negative effect on wildlife, causing drowning, disease proliferation, and habitat destruction. In 2012, hundreds of animals, including many vulnerable one-horned rhinos ( Rhinoceros unicornis ), were killed in floods that swamped Kaziranga National Park in the Indian state of Assam. Unpredictable floods can be harmful even to aquatic life. For example, fish can be displaced and their nests destroyed.

Floods Cause Sedimentation and Erosion Floodwater can also alter the landscape, for instance, by eroding riverbanks and causing them to collapse. As floodwater carries material from the eroded banks, it suspends sediment in the water, which can degrade water quality and lead to harmful blooms of algae. Suspended sediment eventually settles out of the water in a process called sedimentation, which can clog riverbeds and streams, smother aquatic organisms, and destroy habitats. Erosion and sedimentation have a more negative impact on ecosystems that are already degraded or heavily modified. Floods Carry Contamination Floodwater can be contaminated with pollutants such as agricultural pesticides , industrial chemicals, debris, and sewage. If contaminated floodwater enters the ocean it can affect water quality and disrupt delicate ecosystems, such as coral reefs. In February 2019, marine biologists feared for the safety of the Great Barrier Reef off the coast of Queensland, a state in Australia, after it was inundated with polluted floodwater. Floods Spread Diseases Floods are the leading cause of weather-related infectious disease outbreaks. Flooding events increase the chance of spreading waterborne diseases, such as hepatitis A and cholera. Receding floodwater can create stagnant pools of water, which provide the perfect breeding ground for mosquitoes, which can transmit malaria and other diseases. Flood events also lead to an increase in some forms of  zoonosis , such as leptospirosis. Floods Carry Nutrients While floods bring hazards, they also bring nutrients and essential components for life. Seasonal floods can renew ecosystems, providing life-giving waters in more ways than one. Floods transport vital nutrients, such as nitrogen, phosphorus, and organic material, to the surrounding land. When the water recedes, it leaves sediment and nutrients behind on the floodplain. This rich, natural fertilizer improves soil quality and has a positive effect on plant growth, thus increasing productivity in the ecosystem. Ancient civilizations first arose along the deltas of seasonally flooded rivers, such as the Nile in Egypt, because they provided fertile soil for farmland. Floods Recharge Groundwater Floods can replenish underground water sources. Floodwater gets absorbed into the ground then percolates through layers of soil and rock, eventually reaching underground aquifers . These aquifers supply clean freshwater to springs, wells, lakes, and rivers. Ecosystems rely heavily on groundwater during dry spells when it may be the only supply of freshwater available. A good supply of groundwater has a positive impact on soil health and leads to more productive crop and pasture lands. Floods Can Trigger Breeding Events and Migrations Floods can trigger breeding events, migrations, and dispersal in some species. In 2016, thousands of water birds flocked to the Macquarie Marshes in the Australian state of New South Wales. Flooding had filled their wetland habitat for the first time in years, triggering a mass breeding event. In Cambodia, monsoon rains cause an annual flood pulse on the Mekong River that prompts migrations for some animals. The floodwaters cause the Tonle Sap river, which connects the Mekong River to Tonle Sap lake, to reverse its flow, filling the lake. When floodwater enters the lake, it triggers fish migrations, supporting one of the world’s most productive fisheries. Floods Can Boost Fish Stocks Small seasonal floods can be beneficial to native fish stocks and can help those fish outcompete invasive species that are not adapted to the river’s cycles. Sediment deposited on riverbeds during floods can provide a nursery site for small fish. Nutrients carried by floodwater can support aquatic food webs by boosting productivity. Floods Bring Life to Wetlands Wetlands are an extremely important ecosystem; approximately 40 percent of the world’s species rely on them. They filter water, mitigate flooding, and act as a carbon sink . The Okavango Delta in Botswana is a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site and one of the world’s largest, most important wetland habitats. The river captures rainfall from far to the north in the highlands of Angola. This causes a flood pulse that replenishes the wetlands at the height of the dry season, providing a lush oasis in the Kalahari Desert. National Geographic Explorer Steve Boyes, with a team of scientists and Explorers, has participated in a series of expeditions to trace the Okavango from source to sand to protect the waters of this unique habitat. Floods are a force of nature, and their consequences, both positive and negative, are strongly felt by affected ecosystems. Floods can be destructive to humans and the natural environment, but they also help to drive biodiversity and are essential to the functioning of many ecosystems. Whether you regard floods as good or bad, one thing is for certain: The world would be a very different place without them.

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Home > Books > Natural Hazards - Impacts, Adjustments and Resilience

Flood Disaster Hazards; Causes, Impacts and Management: A State-of-the-Art Review

Submitted: 21 June 2020 Reviewed: 17 November 2020 Published: 30 June 2021

DOI: 10.5772/intechopen.95048

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Floods are among disasters that cause widespread destruction to human lives, properties and the environment every year and occur at different places with varied scales across the globe. Flood disasters are caused by natural phenomena, but their occurrences and impacts have been intensified through human actions and inactions. The practice of flood disaster management have evolved over the years from traditional approaches of ad-hoc response measures to integrated approaches involving technologically advanced tools in flood disaster awareness, preparedness and response measures. This chapter proffers understanding into flood disaster awareness, preparedness and management, mitigation and adaptation strategies. Most importantly, the chapter presents a review on the relevance of modern technological tools namely Geographic Information System, Remote Sensing, Internet of Things and Big Data, that are available to flood managers, in the creation of efficient early warnings and Flood decision support systems that elevates the resilience of societies to flood disasters.

• flood disaster
• disaster risk awareness
• disaster risk preparedness
• disaster management
• early warning system

Author Information

Frank jerome glago *.

• Akatsi College for Education, Akatsi, Ghana

*Address all correspondence to: [email protected]

1. Introduction

Disasters can result from forces of nature which may be aided by human actions. Some disasters build up slowly while others may happen suddenly and unexpectedly. Flood disasters can be classified among the quick and sudden disaster types, but are among few in this category that can be well predicted, anticipated and controlled to a great extent.

Floods, like other disasters, do not qualify to be labelled ‘disasters’ by the mere virtue of their happenstances. They do become disasters when they cause damage or adverse effects to human lives, livelihoods and/or properties. Floods are probably the widest spread among the various disaster events that occurs in most countries and causes the most deaths [ 1 ]. Floods, like other disasters, have the ability to cause widespread disturbances in communities, and alter the way of life of people in the affected areas.

The word flood originated from the old English word ‘flod’ akin to the German word ‘flut’ and the Dutch word ‘vloed’ seen as inflow and float of water [ 2 , 3 ]. The Oxford Reference Dictionary (ORD) defines flood as an overflowing or influx of water beyond its normal confines. Floods usually happen when the volume of water within a water body, say, a river or a lake, exceeds its total carrying capacity and as a result, some of the water flow outside the normal perimeter of the water body. Floods occur in almost every part of the world with different intensities and effects. Some of the most notable floods that have occurred include the 1981, 1991 and 2002 floods along the Chiang Jiang (Yangtze) river in China, the Mozambican floods in 2000, the 1983 and 1993 floods on the Mississippi river [ 2 ].

In the summer of 2005, the remarkable flooding brought by Hurricane Katrina which caused more than $ 108 billion in damages, constitute the costliest natural disaster in U.S. history [ 4 , 5 ]. Identified different types of floods namely riverine floods, localized and urban floods, normal flood (e.g. 1-year flood), medium flood (e.g. 5-year flood), severe floods, and catastrophic floods. It is indicated that floods can also be distinguished by their style of occurrence [ 2 ]. Flash floods occur when water quickly sweeps over an area which is difficult to deal with and it is not easy to predict the amount of rain expected within the spatial area over a short period of time [ 2 ].

Regional floods occur when rain falls over a large area for days or weeks causing river levels to rise quickly and fall slowly usually inundating large areas and causing widespread economic losses [ 6 ]. Flash floods are also referred to as upstream floods and regional floods, downstream floods [ 7 ].

There are varied effects of floods. The primary effects of flooding include physical damage to buildings and weakening of structures [ 2 ]. There are instances of loss of human lives and livestock, and the outbreak of disease epidemics. Other effects include instant losses of entire harvest as in the Mozambique flood in 2000 and northern Ghana floods of 2007. Whilst the effects of floods have come to be highly perceived in the negative, it is also true that floods are not entirely of damaging impact on human beings. Flooding can be beneficial such as making the soil more fertile and providing nutrients. Periodic flooding was essential to the development of some of the ancient civilizations especially those along the Tigris-Euphrates rivers, the Nile river, Indus river among others [ 2 ].

2. Causes and impacts of flood disasters

2.1 cause of floods.

Floods happen when soil and vegetation cannot absorb water from downpours. Floods also occur when a river outbursts its banks and the water spills onto the floodplain. Natural processes such as hurricanes, weather systems and snowmelt can cause floods. Other floods following tsunamis and coastal surges have natural causes like earthquakes in the seabed and high tides attributed to the pull of the moon [ 2 ]. There are many human-induced causes of flooding.

Urbanization has also become a major cause of flooding in cities [ 8 ], such that, a river is more likely to flood when its drainage basin is in an urban area. Inadequate drainage in some urban areas is a major cause of flooding [ 3 ], while in others, it is the lack of proper management of the drainage systems. Unplanned urban living has been identified as a significant contributor to flooding events in many developing countries. In a study into causes of flooding in Asamankese in the Eastern region of Ghana by [ 9 ] for instance, a resident succinctly summarises the problems as below;

[T]he main problem in Old Zongo and Abaase areas is the gutters. The gutters are not enough to carry the water when it rains heavily, and secondly, they pour so much rubbish in the gutters, so some of the gutters are also full of rubbish. So, when it rains heavily, where will the water go, it must flood the area. ….the way we build in this area too is a problem. I even think government is not hard on people so we just build anyhow in the waterways. We in this area also experience floods but it is not serious like in Old Zongo areas, that is why we are always trying to tell people here not to build in the waterway, because of what is going on in Old Zongo and Abaase.

This summarises the major contributions of improper managed urbanisation to flooding, a phenomena which characterises many developing countries. In Ghana, for example, perhaps the most devastating flood in the history of the country occurred in its capital, Accra, on 3rd June, 2015 where 159 people lost their lives and several people rendered homeless [ 10 ]. NADMO [ 11 ], suggests that although Ghana is vulnerable to certain disasters, flooding has become the major disaster the country has suffered in recent years especially in its urban areas due to improper management of these spaces [ 12 ].

Figure 1 shows the nature of some gutters in the urban areas of Ghana. Figure 1 shows a partially completed drainage in the flood prone zone of Asamankese, in the Eastern region of Ghana. Most of the gutters in the community, like Figure 1 , are left open and easily gets silted by inflow of sand and other waste materials. The situation of improper management of urban spaces is worse in the major Central Business Districts in many developing countries. Plastic wastes and other debris have been left to clog urban drainage which results in flood disaster when heavy rains are experienced.

Showing a partially completed drain in the Asamankese community, Eastern region of Ghana. Source: Author.

2.2 Impacts of flood disasters

What flood events share in common, is their ability to cause widespread community disruption, displacement, economic loss, property damage, deaths, injury as well as profound emotional suffering. Infrastructure and property, agricultural endeavours as well as historical and cultural sites may also be affected in flood disasters.

According to the United Nations Regional Coordinator in Dakar (October 2007) the worst flooding in 30 years that battered West Africa from July 2007 caused more than 210 death and affected more than 785,000 people [ 12 ].

The aftermaths of flood disasters in Ghana are the large-scale destruction of infrastructure, displacement of people from their dwellings, the loss of human lives, outbreak of diseases and water-borne infections, chemical exposure due to toxic pollutants being released into flood waters, huge loss of investments among other things.

Africa, which is one of the poorest continents in the world (in terms of GDP growth and income) has seen an increase in flood disasters in recent times [ 9 ]. For instance, torrential rains and flooding affected 600,000 people in 16 West African nations in September 2009 [ 13 ]. Countries with most devastating impacts were Burkina Faso, Senegal, and Niger. Another instance include the 2007 floods that displaced more than a million people in Uganda, Ethiopia, Sudan, Burkina Faso, Togo, Mali, and Nigeria, which claimed over 500 lives, and the 2008 floods in Mozambique which killed seven people and displaced tens of thousands residence [ 14 ]. Heavy seasonal rainfall starting in December 2014 also caused flooding in southern Africa [ 15 ]. As of January 2015, 135,000 people were affected by flood hazard in Malawi, Mozambique, Madagascar and Zimbabwe [ 15 ].

The impact of flooding varies both spatially and temporally. It could also be direct or indirect. Rahman [ 16 ] indicated that the direct impacts of floods are closely related to the depth of inundation of floods water. The extent of a flood has a direct relationship for the recovery time of crops, pastures and the social and economic dislocation impact to populations. The impact of floods is considered far reaching with the aftermath effects such as flood-induced disease epidemics. Disease outbreak is common, especially in less developed countries. Malaria, Typhoid and Cholera outbreaks after floods in tropical countries are also common [ 17 ]. [ 9 ] further stated that physical damage to property is one of the major causes for tangible loss in floods. This includes the cost of damage to goods and possessions, loss of income or services in the floods aftermath and clean-up costs. Some impacts of floods, on the other hand, are intangible and are hard to place a monetary figure on. Intangible losses also include increased levels of physical, emotional and psychological health problems suffered by flood-affected people.

According to [ 15 ] the cumulative number of people affected by rains and floods in 2007 in Southern Africa was more than 194,103 persons. This included 60,995 in Malawi (Mostly damage to property and crops), 94,760 people in Mozambique (all were evacuated into resettlement camps); more than 16,680 in Zambia (1890 persons had temporary accommodation, the rest were taken in by host families); and 15,168 in Zimbabwe. An estimated additional 4000 people had been affected in Lesotho and another 2500 persons in Swaziland.

Extreme events affect both the formal and informal economies, making it difficult to assess impacts which include direct and indirect ones. Depending on how well they are constructed and the severity of the event, buildings may be partially or totally destroyed by flooding. A look at Figure 2 will explain the partial damage that often happens to buildings as a result of flooding.

Depicting the impact of flood events o residents’ household in Asamankese, Eastern region of Ghana. Source: Author.

Flood destructions also hit roads and cause delays to infrastructure development initiatives and political processes [ 18 , 19 ] observed that the economic impact of natural disasters shows a marked upward trend over the last decades. The hazards tend to hit communities in developing and least developed countries more. Flood disasters have led to the loss of human life, destruction of social and economic infrastructure and degradation of already fragile ecosystems [ 20 ]. It follows therefore that social impacts include changes in people’s ways of life, their culture, community, political systems, environment, health and wellbeing, their personal and property rights and their fears and aspirations.

Rahman [ 21 ], established that social impacts of floods cause significant problems for the long term functioning of specific types of households and businesses in affected communities. The type of construction influenced the extent of flood damaged (e.g. thatched homes versus concrete high rise buildings will experience different degrees of impact). It follows that vulnerability is a key element in assessing the impact of floods. Different population segments are exposed to varied relative risks because of their socioeconomic conditions of vulnerability. Because of this, disaster reduction has become increasingly associated with practices that define efforts to achieve sustainable development. The links between flood disaster and economic systems, have become another pillar of consideration for sustainable development. Floods, however, cannot be totally prevented but their devastating impacts can surely be significantly minimized if advance warning of the event is available.

3. Flood disaster risk awareness

Disaster risk awareness is the extent of common knowledge of a person or group of persons about disaster risks, the factors that lead to disasters and the actions that can be taken individually or collectively to reduce vulnerabilities to hazards. It also includes the need to build and increase the knowledge and understanding of the many issues about disaster risk reduction, to build the capacity of the people who learn and teach others about the disaster [ 9 ]. Changes in patterns of human behaviour and decision-making at all levels of government and society could, therefore, lead to a substantial reduction in disaster risk [ 22 ]. In this respect, recent experience has shown that public awareness of natural hazards and disaster risk reduction education constitutes a foundation and pre-requisite for effective catastrophic risk management strategies at country and regional levels. More importantly, by influencing human actions and perceptions through societal behaviour and behavioural adaptation, information and education can increase flood risk awareness and play a more effective role in reducing the costs of catastrophes associated with natural perils [ 22 ].

To proffer an understanding on the flood risk awareness of residents in the Asamankese Municipality of Ghana, [ 9 ] surveyed some residents and sought to know how likely the area was susceptible to flood through the major rainy season from March to July. Figure 3 , which summarises the respondents result, pointed out that an overwhelming proportion of respondents (70.0% and 77.5% within the flood prone and Non-flood prone zones respectfully) indicated that flooding has become a regular phenomenon, and the community was likely to be flooded every time it rained.

Showing respondents awareness to flood disaster risk at Asamankese, Eastern region, Ghana. Source: Author.

Awareness is a very crucial element for a society to effectively adapt to a flood risk. As stated by [ 23 ] awareness is diminished when the provision of an appropriate information is minimal or when memories of past experiences or events are diminished. Awareness can generally be uplifted through efforts that are centred on local issues, contain the simple solution to reduce the flood risk and are repeated on a regular basis [ 24 ].

Scholars like [ 25 ] posit that worry is an important risk characteristic that serves as a normative value for awareness. Society can be aware of a flood risk, however, if it is not afraid of the risk, it will not take any action to prepare for it. A higher level of worry is more likely to result in a higher level of awareness and preparedness. There is a positive correlation between these two variables. This was reinforced by [ 26 ] with their assertion that most people become aware and prepared for disasters based on their previous personal experiences with flood disasters. Early warning information can, therefore, allow the disaster managers to be pre-informed and take steps which may significantly reduce the loss of life and damage to property.

4. Flood disaster preparedness and resilience strategies and practices

The argument now is that adequate preparation can make it possible to significantly reduce the impacts of flood disasters through a good understanding of preventive action as well as knowledge of some life-saving techniques during disasters [ 27 ]. Nowhere has the issue of floods become a developmental issue than in poor and developing countries where systemic problems and institutional constraints have increased vulnerability (social, economic and physical) to flood risk and thus, reducing resilience to flood disasters.

Disaster preparedness is defined as the state of taking measures to reduce to the minimum level possible, the loss of human lives and other damages from flood disasters through prompt and efficient actions of response and rehabilitation. That is, preparedness is to put in place the necessary measures for effective and timely response to an event. The objectives of preparedness are to ensure that appropriate mechanisms and resources are in place to assist those afflicted by the disaster and enable them to help themselves [ 9 ].

Flood disaster preparedness consists of a wide range of activities and protective measures that might be instigated from the physically or procedurally. Preparedness is very important in the disaster management process, and includes the knowledge, capacities, activities and measures carried out in advance by governments, professional response and recovery organizations, communities and individuals to effectively anticipate, respond to and recover from the impacts of imminent or current disaster situations or conditions.

The [ 26 ], conceives preparedness as a medium-term plan that involves the development and the implementation of disaster management plans. It involves the development and implementation of early warning systems, resource inventory and stockpiling of resources, coordinating of agencies and ensuring evacuation plans work. Preparedness is seen as tools for ensuring the effective coordination and enhancement of capacities to prevent, to protect, to respond to, recover from and mitigate the devastating effects of natural and man- made disasters [ 9 ].

Apart from personal experiences informing residents’ awareness and preparedness towards flood disasters, external factors such as occupation, level of education of an individual, radio programs and community meetings serve as conduits for disseminating flood information. Hence, these factors may act to increase awareness and preparedness levels to flood disasters.

Studies show that residents’ awareness of flood disaster is usually high. For instance, in [ 9 ]’s study of residents’ level of flood disaster awareness in Asamankese, in Ghana, showed that more than 65 percent of residents in both the Flood prone and Non-flood prone settlements ranked themselves to be at a high risk of flood disasters. Furthermore, the study showed that, the awareness of human factors that exacerbate their risk to flood was also high. However, preparedness of residents’ in most cases were poor, and in Asamankese, like in other developing countries, victims of flood had to usually depend on extended social networks, and government institutions for support to regain their livelihoods after being hit by flood events, a situation which results from their ill preparedness to flood disasters especially financially.

5. Strategies and technologies for improved flood disaster management

5.1 flood disaster management strategies.

Flood Disaster Management Strategies refer to a bundle of processes and activities that are aimed at reducing the overall impacts of floods on societies. Flood management needs to be considered within the overall national development planning strategy of every country and must involve strategic institutional arrangements and collaborations for a sustainable flood management.

The management of floods as problems in isolation almost necessarily results in a piecemeal, localized approach (World Meteorological Organization [ 28 ]). The flood disaster management process should also be coordinated with efforts made in closely related fields. For example, the disaster mitigation process should consider human health impacts during flooding (e.g. cholera, malaria), thereby more effectively address a health issue that arises during and after flooding [ 28 ].

The management of floods takes several approaches ranging from traditional approaches to integrated approaches. The traditional management response to a severe flood was typically an ad- hoc reaction, the quick implementation of a project that considered both the problem and its solution to be distinct and self-evident. Traditional approaches usually gives no thought to the consequences for upstream and downstream flood risks [ 28 ]. Thus, flood management practices have largely focused on reducing flooding and reducing the susceptibility to flood damage. Traditional flood management has employed structural and non-structural interventions, as well as physical and institutional interventions. These interventions have occurred before, during and after flooding, and have often overlapped.

There has been a paradigm shift in flood management. Traditionally, controlling floods has always been the main focus of flood management, with the emphasis on draining flood water as quickly as possible, or storing it temporarily, and separating the river from the population through structural measures such as dams and levees [ 28 ].

The concept of integrated flood management has led to a paradigm shift: absolute protection from floods is a myth, and focus should aim at maximizing net benefits from the use of flood plains, rather than trying to fully control floods [ 28 ].

A proactive approach towards the management of floods over a traditionally reactive approach is rapidly gaining recognition among flood managers. The proactive approach does not treat floods only as an emergency or an engineering problem, but as an issue with social, economic, environmental, legal and institutional aspects. The proactive approach is not limited to a post-event reaction but includes preparedness (including flood risk awareness) and response measures to flood management at different stakeholders’ levels [ 28 ].

Recent calls in flood management are geared at taking a transboundary approach since floods do not respect borders; neither national nor regional or institutional [ 29 ]. The great advantages of transboundary cooperation are that it broadens the knowledge/information base, enlarges the set of available strategies and enables better and more cost-effective solution. Furthermore, widening the geographical area considered by basin planning enables measures to be located where they create the optimum effect [ 29 ].

5.2 Early warning systems

The term ‘early warning’ is used in many fields to describe the provision of information on an emerging perilous circumstance where that information can enable action in advance to reduce the risks involved. The early warning system comprise the set of capacities needed to generate and disseminate timely and meaningful warning information to enable individuals, communities and organizations that are threatened by hazards to take necessary preparedness measures and act appropriately in sufficient time to reduce the possibility of harms or losses [ 30 ].

Early warning systems exist for natural geophysical and biological hazards, complex socio-political emergencies, industrial hazards, personal health risks and many other related hazards. Studies have demonstrated that disaster prevention can pay high dividends and found that for every Euro invested in risk management, broadly 2 to 4 Euros are returned in terms of avoided or reduced impacts on life, property, the economy and the environment [ 31 ]. Early warning systems can be set up to avoid or reduce the impact of flood hazards and other disasters such as, landslides, storms and forest fires and volcanic eruptions. The significance of an effective early warning system lies in the recognition of its benefits by the members of the general public.

Early warning is a major element of flood disaster risk reduction. It saves life and reduces economic and material losses from flood disasters. To be effective, community-based early warning systems need the active involvement of the community people, a strong public education on and awareness of risks, an effective communication system ensuring a constant state of preparedness [ 31 ]. Early warning systems contribute with other Disaster Risk Reduction (DRR) interventions to protect and support sustainable economic development and early detection of undesirable situations. The society benefits from early warning systems if they are in place. Many governments have failed to take early warning into account while formulating their development and disaster risk reduction policies. Subsequently, it results in heavy losses to human lives and economic entities when disasters strike [ 31 ].

A people-centered early warning system necessarily comprises four key elements: (I) knowledge of the risks; (II) monitoring, analysis, and forecasting of the hazards; (III) communication or dissemination of alerts and warnings, and (IV) local capacities to respond to the warnings received. The expression “end-to-end warning system” emphasizes that early warning systems need to span all steps from hazard detection to community response. It is essential to link downstream communities and upstream communities for the effective operation of an early warning system [ 31 ]. There are several instances where early warning systems have helped to mitigate the impact of disasters. As an example, the Bangladesh cyclone preparedness program has successfully warned, evacuated and sheltered millions of people from cyclones since its inception in the early 1970s by the International Federation, the Bangladesh Red Crescent Society and the government of Bangladesh. In the Caribbean, during 2004’s hurricane season, most countries successfully alerted their populations to approaching storms and saved many lives as a result. The key to their success was putting people, not just technology, at the centre of their warning systems. As a result of early warning systems, there were no deaths reported in La Independencia, Guatemala during the hurricane season in October 2005 [ 26 ].

The importance of early warning has been underlined in various UN General Assembly resolutions as a critical element of disaster reduction. Early warning received very high attention after the 26 December 2004 tsunami, when it became clear that a tsunami warning system and associated public education could have saved thousands of lives. The UN Secretary-General in his report; In Larger Freedom: Towards development, security and human rights for all , proposed that the United Nations system should take a leadership role in developing comprehensive global capacities for systematic people-centered early warning systems, which would cover all hazards for all countries and communities. Subsequently, he requested that a global survey is undertaken, with a view to advance the development of a Global Early Warning System (GEWS) for all natural hazards [ 32 ]. Thus early warning systems are very important for disaster management and should be a priority at global, national and local levels.

5.3 Flood disaster mitigation strategies

Flood Disaster Mitigation measures tend to be potentially more efficient long term sustainable solutions to water-related problems and should be enhanced, in particular, to reduce the vulnerability of human beings and goods exposed to flood risk. Flood forecasting and warning is a prerequisite for successful mitigation of flood damage. In the field of environmental engineering, flood mitigation involves the managing and control of flood water movement, such as redirecting flood run-off through the use of floodwalls and flood gates, rather than trying to prevent floods altogether. It also involves the management of people, through measures such as evacuation and dry/wet proofing properties for example. The mitigation of flooding can be done on an individual, community and at city authority or national levels.

5.4 Flood disaster adaptation strategies

Flood disaster adaptation refers to actual adjustments made that are geared towards mitigating the severity of flood disasters. Flood disaster adaptation strategies vary from before flood adaptation, during flood adaptation, to post flood adaptation strategies. It also ranges from individual, community, to citywide adaptation strategies. Discussions on flood adaptation strategies pointed out that embankments, for instance, either concrete or sandy may be constructed to prevent water from entering residential houses [ 33 ]. Adaptation options that would be effective for flood disaster in developing nations include Environmental policy reforms, changes in urban and housing design, removal of laws that can inadvertently increase flood vulnerability [ 34 ]. Capacity building is also required to integrate climate change and its impact on urban development planning, engaging local communities, raising public awareness and education on climate change and enabling wider representation at stakeholder meetings. Planting of vegetative cover to reduce runoff speed, terracing hillsides to slow flow down hills as well as control of man-made channels to divert flood water among others, serve as adaptation strategies. Generally, adaptation strategies adopted in flood disasters range from structural to non-structural [ 35 ].

5.5 Monitoring, evaluation and mainstreaming of flood disaster management

Being able to count on institutionalized capacities to mobilize and coordinate resources when and where they are needed is crucial in all phases of the disaster cycle, sometimes with very little room for delay or errors of judgment. Coordination among agencies and stakeholder groups is important for flood mitigation, in particular, the design and execution of programmes and policies to help address underlying causes of extreme vulnerability [ 36 ]. Monitoring of activities is necessary because there is often the need to link responsibilities and budgets for programmes over time. The performance of institutions and organisations responsible for disaster management should be monitored and evaluated on a regular bases. The relevance of monitoring and evaluation as a means of reducing flood disaster events cannot be overemphasised.

The capacity to monitor and evaluate flood prevention, mitigation, relief and recovery operations and institutional arrangements would create opportunities for learning and improve the accountability of authorities [ 36 ]. Monitoring is a key element in pre-flooding, flooding and post flooding stages of flood disaster management. Evaluation goes hand in hand with monitoring to assess the impact of flooding and the effects of key interventions engaged in mitigating the impact of flooding on people, infrastructure, and the environment in general. In a study on the environmental aspects of integrated flood management, [ 28 ], noted that adaptive management requires continuous monitoring of the state of the environment and evaluation at regular intervals.

The importance of monitoring has been recognized from various perspectives [ 28 ] Pre-plan monitoring of various natural processes provides the basic input for assessment of resource, risks and development options. Monitoring at a development planning level is based on actions taken in line with selected plan and factors of environmental impacts indicated in environmental assessment at the strategic level [ 28 ]. In the context of awareness of flood hazards, monitoring encapsulates awareness of causes and how these causes change over time, knowledge of interventions and how these interventions are shaping the frequency and nature of flood events in an area. Monitoring is essential in flood management from a first-hand point of providing timely and efficient early warning information. Immediate and post-implementation monitoring is important in order to assess whether the flood management measure has succeeded [ 28 ].

Mainstreaming of disaster risk reduction into development planning, policy, and implementation should be at the heart of every sustainable Development Planning agenda. Disasters, such as floods, have an enormous impact on development. There is, therefore, the need for mainstreaming disaster planning into development planning. The importance of mainstreaming is also recognized by the Hyogo Framework for Action (HFA) adopted at the World Conference for Disaster Risk Reduction (WCDRR), where integration of disaster risk reduction into the development programmes is a priority [ 5 ]. There has been increasing recognition by both governments and donors for the need to mainstream disaster risk reduction into development planning [ 37 ]. Mainstreaming disaster planning into development planning considers risks emanating from natural hazards in medium-term strategic development frameworks, in legislations and institutional structures, in sectoral strategies and policies, in budgetary processes, in the design and implementation of individual projects and in monitoring and evaluating all of the above [ 37 ].

5.6 Sustainable flood management

The concept of sustainable development is firmly rooted in all flood management. Sustainable flood management involves: ensuring quality of life by reducing flood damages but being prepared for floods, mitigating the impact of risk management measures on ecological systems at a variety of spatial and temporal scales, the wise use of resources in providing, maintaining and operating infrastructure and risk management measures, maintaining appropriate economic activity [ 38 ]. Sustainable flood management as a concept is not new, its methods have been practiced on many continents for years [ 39 ]. With increasing scrutiny of traditional engineering solutions, there is a growing realisation throughout the world that there is a huge and urgent need for pro-active and sustainable flood management solutions.

The notion of sustainability in the context of flood management is still rather ambiguous but generally embraces economic, environmental and social objectives. Sustainable flood management therefore refers to the provision of possible social and economic resilience against flooding, by protecting and working with the environment, in a way which is fair and affordable both now and in the future [ 40 ]. In practice a sustainable approach should integrate a range of flood management requirements using best practices and involving the economics of a scheme, good planning, understanding flood generation processes, protecting natural environments and working with communities [ 39 ]. Sustainable flood management is, therefore, an integrated set of procedures linked into a physical catchment.

6. Technological advancements in flood disaster management

Advanced technologies have been developed and integrated into higher institutional level decision support systems to aid the prediction, monitoring and management of flood disasters in some countries. These advanced flood decision support systems’ architecture include technologies such as Geographic Information Systems, remote sensing and photogrammetry, and hydrologic models.

The Flood Decision Support System (FDSS) refers to interactive computing environment designed for specific contexts which include interlinked models/analytical tools, databases, graphical user interfaces and other systems. The FDSSs according to [ 41 ] have the potential to improve flood disaster assessment and mitigation through improved data collection and rapid dissemination of flood information to affected areas. For an effective FDSS on the technology aspect of disaster management, analysts have to ensure effective interoperability of the technologies. This will ensure that, all aspects of the technology that singularly may be responsible for data capture, storage, manipulation, analysis, retrieval or display of information, work in a smooth interwoven network and relay information to other parts of the system without technical hindrances to ensure the overall goal is achieved.

There are three main components to the Flood Disaster Support System. These include the Database component, the Modelling component, and the Display component also known as the Graphical User Interface (GUI) component. The Database component of the FDSS comprises the data used in the modelling functions. This component uses to tools to capture and store flood related data. Some data stored include historical rainfall data, geological data, soil and ecological data, population data, boundary and administrative data. Tools used in data capture for the Database varies depending on the data to be captured. For example, Remote sensing techniques are used to capture satellite data on flood zones, flood buffer zone monitoring. Sensors are also deployed to monitor flow, volume and carrying capacities of rivers while rain gauges capture precipitation volumes. These data may be complemented with census data on population and livelihoods of residents. All these various data are kept in the Database component of the DSS.

The second component of the FDSS are functions of analytics and modelling. Various analysis are carried out and the data in the database taking through several processes of manipulation. These processes of data manipulation and analysis differ in approach and are tailored to meet various goals in the decision making process. Prominent among the tools used at this stage is Geographic Information Systems (GIS) tools. Regarding flood modelling, advanced tools available to flood managers include advanced technological tools in soft computing, for instance, evolutionary computing, as well as probabilistic predictions techniques of inundation recurrence intervals [ 41 ]. These tools afford flood managers varieties of techniques that can be applied in simulation, modelling, analysis and management of flood.

The User Interface component of the FDSS provides flood decision makers an interactive graphical interface, enabling users to query the data stored in the system. It again enable users to display and visualise the models and reports from the manipulations of the data. This component of the advanced FDSS enables users to prepare and appreciate maps and animations of the hydrologic phenomena being studied.

6.1 Remote sensing and geographic information systems in disaster management

Advances in remote sensing tools and techniques over the past few years have provided disaster managers, especially flood disaster managers with powerful tools in the acquisition of flood sense data, in forecasting and monitoring of flood occurrences and in the management of watersheds, rivers and wetland areas.

Remote sensing refers to the Science of obtaining information about objects, areas or phenomena from a distance [ 42 ]. Typically, these information are collected through sensors that are planted on aircrafts or satellites. In flood disaster management, remote sensing can be applied to monitor and map events such as changes in river volume, changes in coastline, map wetlands and flood prone zones and boundaries of inundation.

A Geographic Information System(s) (GISs) refers to a framework for gathering, managing and analysing location-based data. This framework is used to analyse and organize several distinct layers of location-based information into concise visualizations through maps and 3D scenes. Ultimately, GISs present powerful capabilities that proffer deeper insights into data, which may include revelation of patterns and relationships for smarter decision making [ 43 ].

Reliable flood maps are therefore produced using GIS techniques and remotely sensed data to manage floods. GIS tools aid in the preparations to Digital Elevation Models (DEMs) for high level hydrological modelling using sensors such as The Light Detecting and Ranging (LiDAR) sensors.

With the help of data interpretation techniques of GIS, remotely-sensed imageries are interpreted to create suitable flood risk mitigation frameworks and FDSSs. Although flood disasters have increased in scale and frequency in recent years, there has been a commensurate improvement in flood data capturing and analyses techniques, that when applied in time, can significantly mitigate the risks and impacts of floods. As summarised in Table 1 , GIS and RS are of great importance in the pre and post disaster management processes.

Showing GIS and Remote Sensing Application in flood disaster management. Source: Authors’ Construct with reference to [ 44 ].

6.2 Internet of Things (IoT) and Big Data in flood disaster management

The Internet of Things (IoT) refers to a network of devices connected over the internet to sense, track and respond to issues. Patel and Patel [ 45 ] defines the IoT as “ a type of network to connect anything with the internet based on stipulated protocols through information sensing equipment to conduct information exchange and communications in order to achieve smart recognitions, positioning, tracing, monitoring and administration.”

The network of physical objects are able collect data on a regular bases and in a structured form, perform high level analysis and predict changes, as well as initiate actions based on results from the analyses. IoT is hence a powerful technological tool that can provide a wealth of high level intelligence which is needed in planning and management.

There are three levels of IoT. The first is people to people interconnectivity, the second is people to machine interconnectivity and the third being machine to machine or things to things interconnectivity [ 45 ]. In all interconnectivity of things and people, the internet remains the main driver. This interconnectivity of Things, enables the swift transmission of meteorological, hydrological and geological data pertaining to flood events.

In flood disaster management, providing a quick feedback on the occurrence of floods can be a great step in preventing and mitigating flood disasters and their impact on livelihoods in society. Deploying IoT in flood management puts disaster managers at a position to create enhanced early warning systems that do not only measure the water levels and the speed of inundation, but early warning systems that could also send alerts to residents and flood managers through mobile phones and other personal electronic devices, and additionally, prescribe the best prevention and mitigation strategies based on data such as direction of runoff, speed of rise of water levels and the time at the disposal of residents to take necessary action.

Big Data on the other hand, refers to “ the evolution and use of technologies that provide the right user at the right time with the right information from a mass of data that has been growing exponentially for a long time in our society ” [ 46 ]. Digital data collection has not only seen growth in volume but also in variety in storage formats, hence Big Data is often described as high-volume, high-velocity and/or high variety information assets that demand cost-effective, innovative forms of information processing to enable enhanced insight, decision making and process automation [ 47 ].

Big data typically defines data that exceeds the storage, processing and computing capacity of conventional database [ 46 ]. Hence Big Data analytics typically involves automated software that assist in the collection, organisation and analysis of the data being generated to discover trends, correlations and other useful results to prompt necessary action.

Through Big data process automation, precipitation data, soil moisture data, temperature data, water content data of water bodies, data on evapotranspiration, ground water data, etc., are collected and processed in real-time without human supervision to make predictions and early warnings about flood disasters’ occurrence [ 47 ].

7. Conclusion

Flood disasters have had very devastating impacts on societies and have destroyed livelihoods and investments of staggering monetary value and importance to development. However, adequate involvement of technology are leading to the creation of people-centered early warning systems that enhances residents’ awareness and preparedness to flood events to significantly reduce the adverse impacts of these disasters on people. This chapter discussed various aspects of flood disaster management including early warning systems, flood mitigation and adaptation strategies, the relevance of monitoring, evaluation and mainstreaming flood disaster management into national level development planning. The chapter again discussed and encourage the integration of advanced technological tools into the frontier of flood disaster management, as these tools have the capacity to capture, analyse and disseminate real-time flood data to all stakeholders to safeguard lives and precious investments.

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© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Flood Essay

Floods are natural disasters that occur when a body of water, such as a river or ocean, overflows its banks and spills onto the surrounding land. This can happen for a variety of reasons, including heavy rainfall, melting snow, and storms . Here are a few sample essays on floods.

100 Words Essay on Floods

Floods are naturally occurring phenomena that are caused due to overflowing water bodies. A flood can be just a small occurrence that can cause some travel issues to highly destructive events that can cause significant damage to homes, businesses, and infrastructure. In addition to physical damage, floods can also lead to loss of life and can have long-term impacts on the affected communities.

To protect against floods, people can take steps such as building floodwalls and levees and elevating homes and other structures in flood-prone areas. It is also important for individuals to be prepared for floods by having an emergency plan in place and staying informed about potential flooding in their area.

200 Words Essay On Floods

Floods are natural disasters that occur due to overflowing water sources like ponds, oceans and rivers. The reasons for the occurrence of floods can be heavy rainfall, loose soil, melting of snow, breaking of dams etc.

Impact | The impacts of floods can be far-reaching and long-lasting. In addition to physical damage to homes, businesses, and infrastructure, floods can also lead to loss of life. Floodwaters can carry dangerous debris and pollutants, making them a health hazard for people and animals. Floods can also have economic impacts, as they can disrupt transportation and commerce, and can destroy crops and other sources of food.

Prevention | People living nearby water bodies take preventative measures to reduce the impact of flood damage. Building elevated homes, planting more trees to soak up an extra amount of water, having an escape plan in case of emergencies etc. It is also important for individuals to be prepared for floods by having an emergency plan in place and staying informed about potential flooding in their area. In the event of a flood, it is important to follow the advice of local authorities and evacuate if instructed.

Overall, floods are serious natural disasters that can have significant impacts on communities. By taking steps to protect against floods and being prepared for them, people can reduce the risks and impacts of this type of disaster.

500 Words Essay on Floods

Floods are a common natural disaster that occurs when excess water overflows onto land that is normally dry. This can happen for a number of reasons, including heavy rainfall, snowmelt, and coastal storms.

Types Of Floods

There are several different types of floods, each with its own characteristics and potential impacts. Flash floods, for example, are caused by sudden, intense rainfall and can happen within minutes or hours. They can be particularly dangerous because they often catch people off guard and can lead to flash flooding in urban areas.

On the other hand, river floods are caused by water flowing over the banks of rivers and streams. These floods can be more gradual, giving people time to evacuate and prepare, but they can also be very destructive.

Coastal floods, also known as storm surges, are caused by strong winds and high tides associated with coastal storms, such as hurricanes. These floods can be extremely destructive, as they can cause not only flooding but also strong winds and waves that can damage buildings and infrastructure.

Biggest Floods Recorded On Earth

One of the biggest floods in history was the 1931 China floods , also known as the Central China Floods . These floods were caused by heavy rainfall and the collapse of the Banqiao Dam. The floods affected an estimated 54 million people and resulted in the deaths of 145,000 people.

Another major flood was the 1993 Mississippi River Flood , which affected parts of the United States, including Missouri, Illinois, and Kentucky . The floods were caused by heavy rainfall and resulted in the deaths of 50 people and caused billions of dollars in damages.

In 1998, the Yangtze River Flood in China also caused widespread destruction. The floods, which were the result of heavy rainfall, affected millions of people and resulted in the deaths of over 4,000 people. The floods also caused billions of dollars in damages.

Another recent and devastating flood was the 2010 Pakistan floods, which affected the Indus River Basin in Pakistan. The floods, which were caused by heavy monsoon rains, affected an estimated 20 million people and resulted in the deaths of over 1,700 people.

Forest To Prevent Floods

Forests play a critical role in preventing floods. Trees and other vegetation in forests can act as natural barriers which absorb water. Hence, reducing the speed of flowing water and thereby reducing the risk of flooding.

When it rains, the leaves and branches of trees absorb a significant amount of water. The roots of trees also help to hold the soil in place, preventing it from eroding and being carried away by the water. This helps to reduce the amount of water that flows over the surface and into rivers and streams, lowering the risk of flooding.

In addition to absorbing water, forests also help to regulate the flow of water by releasing it slowly into rivers and streams. This helps to prevent sudden, large increases in water levels that can lead to flooding. Trees and other vegetation can help to reduce the force of the water and protect against erosion, which can help to minimise the damage caused by floods.

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Floods, explained

Floods are among Earth's most common–and most destructive–natural hazards.

There are few places on Earth where flooding is not a concern. Any area where rain falls is vulnerable to floods, though rain is not the only cause.

How floods form

A flood occurs when water inundates land that's normally dry, which can happen in a multitude of ways.

Excessive rain, a ruptured dam or levee , rapid melting of snow or ice, or even an unfortunately placed beaver dam can overwhelm a river, spreading over the adjacent land, called a flood plain . Coastal flooding occurs when a large storm or tsunami causes the sea to surge inland .

Most floods take hours or even days to develop, giving residents time to prepare or evacuate. Others generate quickly and with little warning. So-called flash floods can be extremely dangerous , instantly turning a babbling brook or even a dry wash into rushing rapids that sweep everything in their path downstream.

Climate change is increasing the risk of floods worldwide, particularly in coastal and low-lying areas, because of its role in extreme weather events and rising seas . The increase in temperatures that accompanies global warming can contribute to hurricanes that move more slowly and drop more rain , funneling moisture into atmospheric rivers like the ones that led to heavy rains and flooding in California in early 2019.

Meanwhile, melting glaciers and other factors are contributing to a rise in sea levels that has created long-term, chronic flooding risks for places ranging from Venice, Italy to the Marshall Islands . More than 670 U.S. communities will face repeated flooding by the end of this century , according to a 2017 analysis; it's happening in more than 90 coastal communities already.

Dramatic pictures reveal Venice flooding

Impacts of flooding

Floods cause more than $40 billion in damage worldwide annually, according to the Organization for Economic Cooperation and Development . In the U.S., losses average close to $8 billion a year. Death tolls have increased in recent decades to more than 100 people a year . In China's Yellow River Valley some of the world's worst floods have killed millions of people.

When floodwaters recede, affected areas are often blanketed in silt and mud. The water and landscape can be contaminated with hazardous materials such as sharp debris, pesticides, fuel, and untreated sewage. Potentially dangerous mold blooms can quickly overwhelm water-soaked structures.

Residents of flooded areas can be left without power and clean drinking water, leading to outbreaks of deadly waterborne diseases like typhoid, hepatitis A, and cholera. ( Learn here about flood preparation and safety tips .)

Flood prevention

Flooding, particularly in river floodplains, is as natural as rain and has been occurring for millions of years. Famously fertile floodplains such as the Mississippi Valley, the Nile River Valley in Egypt, and the Tigris-Euphrates in the Middle East have supported agriculture for millennia because annual flooding has left tons of nutrient-rich silt deposits behind. Humans have increased the risk of death and damage by increasingly building homes, businesses, and infrastructure in vulnerable floodplains.

To try to mitigate the risk, many governments mandate that residents of flood-prone areas purchase flood insurance and set construction requirements aimed at making buildings more flood resistant—with varying degrees of success.

Massive efforts to mitigate and redirect inevitable floods have resulted in some of the most ambitious engineering efforts ever seen, including New Orleans's extensive levee system and massive dikes and dams in the Netherlands. Such efforts continue today as climate change continues to put pressure on vulnerable areas. Some flood-prone cities in the U.S. are even going beyond federal estimates and setting higher local standards for protection .

For Hungry Minds

Related topics.

• FLOOD CONTROL
• CLIMATE CHANGE

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How Is Climate Change Affecting Floods?

Like other extreme weather disasters, flooding involves a number of competing factors that may affect its frequency and intensity.

• Share full article

By Elena Shao

• July 10, 2023

Floods can surge all year round, in every region of the world. But discerning the relationship between any given flood and climate change is no small feat, experts say, made difficult by limited historical records, particularly for the most extreme floods, which occur infrequently.

It can be tempting to attribute all floods and other extreme events to the forces of warming planet. But weather is not climate, even though weather can be affected by climate. For example, scientists are confident that climate change makes unusually hot days more common. They’re not as sure that climate change is making tornadoes more severe .

Floods fall somewhere along the confidence spectrum between heat waves (“yes, clearly”) and tornadoes (“we don’t know yet”), said Daniel Swain, a climate scientist at University of California, Los Angeles. “I’d say, ‘yes, probably, but…’”

Flooding, like other disasters, involves a number of competing factors that may affect its frequency and intensity in opposing ways. Climate change, which is worsening extreme rainfall in many storms, is an increasingly important part of the mix.

What causes floods

Several main ingredients contribute to flood development: precipitation, snowmelt, topography and how wet the soil is. Depending on the type of the flood, some factors may matter more than others.

For example, a river flood, also known as a fluvial flood, occurs when a river, stream or lake overflows with water, often following heavy rainfall or quickly melting snow. A coastal flood occurs when land areas near the coast are inundated by water, often following a severe storm that collides with high tides.

Flooding can also happen in areas with no nearby bodies of water. Flash floods, in particular, can develop anywhere that experiences intense rainfall over a short period of time.

How floods are measured

Many metrics are used to measure floods, including stage height (the height of the water in a river relative to a specific point) and flow rate (how much water passes by a specific location over a particular time period).

To describe the severity of a flood, though, experts will often use the more simple term “a 100-year flood,” to describe a flood that has a 1 percent chance of striking in any given year, considered an extreme and rare occurrence. The term is just a description of likelihood, though, not a promise. A region can have two 100-year floods within a few years.

Have floods increased in past decades?

Not exactly. Climate change has undoubtedly intensified heavy precipitation events, but, unexpectedly, there has been no corresponding increase in flood events .

When it comes to river floods, climate change is likely exacerbating the frequency and intensity of the extreme flood events, but decreasing the number of moderate floods, researchers found in a 2021 study published in Nature .

As the climate warms, higher rates of evaporation cause soils to dry out more rapidly. For those moderate and more commonplace floods, the initial conditions of soil moisture is important, since drier soils may be able to absorb most of the rainfall.

With larger flood events, that initial soil moisture matters less “because there’s so much water that the soil wouldn’t be able to absorb all of it, anyway,” said Manuela Brunner, a hydrologist at the University of Freiburg in Germany and the lead author of the 2021 study. Any additional water added past the point where the soil is fully saturated will run off and contribute to flood development, Dr. Brunner said.

Looking to the future

Scientists are confident some types of flooding will increase in the “business as usual” scenario where humans continue warming the planet with greenhouse gas emissions at the current rate.

First, coastal flooding will continue to increase as sea levels rise. Melting glaciers and ice sheets add volume to the ocean, and the water itself expands as it warms.

Second, flash flooding will continue to increase as there are more extreme precipitation events. Warmer temperatures increase evaporation, putting more moisture into the atmosphere that then gets released as rain or snowfall.

Researchers also expect that, as the climate warms, flash floods will get “flashier,” meaning that the timing of the floods will get shorter while the magnitude gets higher. Flashier floods can be more dangerous and destructive.

Flash floods may also increasingly follow catastrophic wildfires in a deadly cascade of climate disasters. That’s because wildfires destroy forests and other vegetation, which in turn weakens the soil and makes it less permeable.

If heavy rains occur on land damaged by a fire, the water “does not get absorbed by the land surface as effectively as it once did,” said Andrew Hoell, a meteorologist at the National Oceanic and Atmospheric Administration’s Physical Sciences Lab.

Though it may be counterintuitive to see the two extremes, too much fire and too much water, in the same region, the sight will most likely become more common, particularly in the American West.

Are different areas experiencing flooding?

In a recent paper published in Nature , researchers found that in the future, flash floods may be more common father north, in Northern Rockies and Northern Plains states.

This poses a risk for flood mitigation efforts, as local governments may not be aware of the future flash flood risk, said Zhi Li, lead author of the 2022 study.

The pattern is driven by more rapidly melting snow, and snow that melts earlier in the year, Dr. Li said. Regions at higher latitudes may experience more “rain-on-snow” floods like those that surged through Yellowstone in June .

Elena Shao is a reporter and graphics editor based in New York. More about Elena Shao

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• Review Article
• Published: 10 August 2021

Causes, impacts and patterns of disastrous river floods

• Bruno Merz   ORCID: orcid.org/0000-0002-5992-1440 1 , 2 ,
• Günter Blöschl 3 ,
• Sergiy Vorogushyn   ORCID: orcid.org/0000-0003-4639-7982 1 ,
• Francesco Dottori   ORCID: orcid.org/0000-0002-1388-3303 4 ,
• Jeroen C. J. H. Aerts   ORCID: orcid.org/0000-0002-2162-5814 5 , 6 ,
• Paul Bates 7 ,
• Miriam Bertola   ORCID: orcid.org/0000-0002-5283-0386 3 ,
• Matthias Kemter 1 , 2 , 8 ,
• Heidi Kreibich 1 ,
• Upmanu Lall   ORCID: orcid.org/0000-0003-0529-8128 9 &
• Elena Macdonald   ORCID: orcid.org/0000-0003-0198-6556 1  

Nature Reviews Earth & Environment volume  2 ,  pages 592–609 ( 2021 ) Cite this article

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• Natural hazards

Disastrous floods have caused millions of fatalities in the twentieth century, tens of billions of dollars of direct economic loss each year and serious disruption to global trade. In this Review, we provide a synthesis of the atmospheric, land surface and socio-economic processes that produce river floods with disastrous consequences. Disastrous floods have often been caused by processes fundamentally different from those of non-disastrous floods, such as unusual but recurring atmospheric circulation patterns or failures of flood defences, which lead to high levels of damage because they are unexpected both by citizens and by flood managers. Past trends in economic flood impacts show widespread increases, mostly driven by economic and population growth. However, the number of fatalities and people affected has decreased since the mid-1990s because of risk reduction measures, such as improved risk awareness and structural flood defences. Disastrous flooding is projected to increase in many regions, particularly in Asia and Africa, owing to climate and socio-economic changes, although substantial uncertainties remain. Assessing the risk of disastrous river floods requires a deeper understanding of their distinct causes. Transdisciplinary research is needed to understand the potential for surprise in flood risk systems better and to operationalize risk management concepts that account for limited knowledge and unexpected developments.

The causative mechanisms of floods with disastrous consequences tend to be different from those of non-disastrous floods, and show anomalies in one or several flood- and loss-generating processes.

Past trends in flood hazard show both upward and downward changes. In some regions, anthropogenic warming is already strong enough to override other drivers of change.

Flood hazards and impacts are projected to increase for many regions around the globe. Future flooding hotspots are expected in Asia and Africa, owing to climate and socio-economic changes.

Reducing vulnerability is a particularly effective way of reducing flood impacts. Global decreases in flood-affected people and fatalities since the mid-1990s (despite a growing population) are signs of effective risk reduction.

Disastrous floods often come as a surprise. Effective risk reduction requires an understanding of the causative processes that make these events distinct and to address the sources of surprise, including cognitive biases.

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Acknowledgements

This work was supported by the DFG projects ‘SPATE’ (FOR 2416) and ‘NatRiskChange’ (GRK 2043/1), the FWF ‘SPATE’ project (I 3174), the ERC Advanced Grant ‘FloodChange’ project (number 291152), the Horizon 2020 ETN ‘System Risk’ project (number 676027) and the Helmholtz Climate Initiative. P.B. was supported by a Royal Society Wolfson Research Merit award. J.C.J.H.A. was supported by an ERC Advanced Grant COASTMOVE (number 884442) and a NWO-VICI grant (number 453-13-006).

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B.M. suggested the original concept and coordinated the writing. G.B., S.V. and F.D. made major contributions to the writing. B.M., M.K., E.M. and S.V. generated the figures. All authors discussed the concepts and contributed to the writing.

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Supplementary information.

(AAL). A widespread indicator for risk, it is the estimated average loss per year considering the full range of scenarios from frequent events (zero or small loss) to extreme events (large loss or worst-case scenario).

Fall of rain onto existing snow, leading to flood runoff composed of snowmelt and rainfall.

Long, narrow and transient corridors of strong horizontal water vapour, transporting on average more than double the flow of the Amazon river and delivering moisture as heavy precipitation.

The fraction of the event water input (precipitation or snowmelt within the catchment) that is not retained in the catchment and that directly contributes to discharge during the event.

Consequences occurring in the inundated region during a flooding event.

Consequences occurring far away from the flooded region and/or after a flooding event.

Consequences of a flooding event that are difficult or impossible to monetarize, such as loss of life or loss of memorabilia.

The ratio of the number of people who lose their lives in a flood to the number of people affected by the flooding event.

The highest streamflow peak in each year.

The dates of the year when floods occur.

The distance over which flooding occurs simultaneously.

Level at which a flood causes extensive inundation, significant evacuations, or property transfer to higher ground.

Level at which a flood does not cause damage but requires mitigation action in preparation for more substantial flooding.

According to the DFO, either the total number of people left homeless after the incident, or the number of people evacuated during the flood.

Coupled Model Intercomparison Project Phase 5; for coordinated climate change experiments for the Fifth Assessment Report AR5 of the Intergovernmental Panel on Climate Change and beyond.

An indicator expressing the exceedance probability or rarity of an event. For instance, a 100-year flood discharge has a probability of 1/100 of being exceeded in a given year.

Relation between flood discharge and the associated return period.

Optimizing risk reduction measures based on the best available knowledge.

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Merz, B., Blöschl, G., Vorogushyn, S. et al. Causes, impacts and patterns of disastrous river floods. Nat Rev Earth Environ 2 , 592–609 (2021). https://doi.org/10.1038/s43017-021-00195-3

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Flood Hazard, Vulnerability and Risk Assessment for Different Land Use Classes Using a Flow Model

• Original Article
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• Published: 05 December 2019
• Volume 4 , pages 225–244, ( 2020 )

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• Md Abdullah Al Baky 1 ,
• Muktarun Islam 2 &
• Supria Paul 3  

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This study is concerned with flood risk that can be assessed by integrating GIS, hydraulic modelling and required field information. A critical point in flood risk assessment is that while flood hazard is the same for a given area in terms of intensity, the risk could be different depending on a set of conditions (flood vulnerability). Clearly, risk is a function of hazard and vulnerability. This study aims to introducing a new approach of assessing flood risk, which successfully addresses this above-mentioned critical issue. The flood risk was assessed from flood hazard and vulnerability indices. Two-dimensional flood flow simulation was performed with Delft3D model to compute floodplain inundation depths for hazard assessment. For the purpose of flood vulnerability assessment, elements at risk and flood damage functions were identified and assessed, respectively. Then, finally flood risk was assessed first by combining replacement values assessed for the elements and then using the depth–damage function. Applying this approach, the study finds that areas with different levels of flood risk do not always increase with the increase in return period of flood. However, inundated areas with different levels of flood depth always increase with the increase in return period of flood. The approach for flood risk assessment adopted in this study successfully addresses the critical point in flood risk study, where flood risk can be varied even after there is no change in flood hazard intensity.

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1 Introduction

This study is concerned with how we can assess flood risk in a given flood prone area. There are many examples of flood studies in different countries. Bangladesh is one of those countries where a significant number of studies have been carried out with flood issue. This research selected Bangladesh for the purpose of assessing flood risk.

Bangladesh is a deltaic country located at the lower part of the basins of the three mighty rivers—the Ganges, the Brahmaputra and the Meghna. This unique geographical setting, surrounded by mountains on three sides, together with extremely flat and low-lying floodplain topography, a low-lying coastline, and an extreme climate variability has rendered the country highly prone to natural hazards such as flood (Chowdhury et al. 1997 ; Hoque et al. 2011 ; Islam et al. 2010 ). About one-fifth to one-third of the country is annually flooded by overflowing rivers during pre-monsoon (April to May) and monsoon (June to September) periods. These floods cause physical damages to agricultural crops, buildings and other infrastructure, social disruptions in vulnerable groups, livelihoods and local institutions, and direct and indirect economic losses (Baky et al. 2012 ; Bhuiyan and Dutta 2012 ; Mirza 2011 ). The flood hazard problem in recent times is getting more and more frequent and acute due to growing population size and human interventions/socio-economic activities in the floodplain at an ever-increasing scale (Bhuiyan and Baky 2014 ; Paul and Routray 2010 ).

Flood mitigation approaches in Bangladesh have ranged from structural interventions (embankment, flow regulation structures, etc.) to non-structural approaches (forecasting and warning, flood preparedness before during and after the flood, flood proofing measures, etc.) (Paul and Routray 2010 ; Rahman and Salehin 2013 ). The Flood Action Plan (FAP) and French Engineering Consortium (FEC) conducted a feasibility flood control survey and a hydrological study in Bangladesh. They focused on agricultural adjustment processes (Younus 2012 ) and the impacts of floods when flood adaptation fails at the community level (Younus and Harvey 2014 ). Structural flood protecting projects even though have short-term positive impacts, the viability of those projects made over the years has often faced criticism because of their adverse hydraulic, environmental and socio-economic impacts (Burrel et al. 2007 ; Chowdhury et al. 1997 ; Shaw 2006 ). Those projects cause economic hardship to the poorer community of the society, which are dependent on many free resources (e.g. fisheries) of river (Chowdhury et al. 1997 ; Chowdhury 2010 ) and even on water transport by country boats (Hunting 1992 ). Furthermore, the benefits of structural flood control projects cannot be reached at all level of society. For example, aquaculture activities are becoming popular particularly in the coastal region of Bangladesh (Sohel and Ullah 2012 ) as polder-based flood control project is developing in the region. However, it is still unlikely for the marginal population to engage in such aquaculture activities since the activities need sufficient capital to start.

The experiences with structural flood control interventions gave way to new insights, which are a combination of structural and non-structural flood hazard mitigation measures depending on the specific local or regional needs (Van Alphen and Lodder 2006 ). Very recently, Bangladesh government has focused on both structural and non-structural flood management approaches to reduce vulnerability to flooding in the country (Paul 1995 , 1997 ; Paul and Hossain 2013 ). Preparation of flood risk maps is the basic requirement before non-structural flood hazard mitigation approaches (Bhuiyan and Baky 2014 ; Bhuiyan et al. 2014 ; Demir and Kisi 2016 ; Giustarini et al. 2015 ; Hoque et al. 2011 ; Islam et al. 2010 ; Islam and Sado 2000 ). Flood risk mapping facilitates the administrators and planners to identify areas vulnerable to flood hazard and to determine infrastructure at risk and the degree they might be affected, and to map their capacity to respond and recover (Bhuiyan and Baky 2014 ; Bhuiyan et al. 2014 ; Hazarika et al. 2018 ; Sanyal and Lu 2009 ; Tran et al. 2009 ; Vojtek and Vojteková 2016 ). Most importantly, it helps in identifying and prioritizing the mitigation and response efforts and helps to inform emergency responses (Tran et al. 2009 ).

Despite having mentionable positive options of flood risk map, the study of flood risk mapping is limited. Chowdhury and Karim ( 1996 ) studied on risk-based zoning of storm surge prone area of the Ganges tidal plain. Hazard factors were based on simulated spatial distribution of 100-year flood depths, while the vulnerability factors were based on the distribution of population densities. Risk indices were then derived as a product of hazard and vulnerability factors as per Skakun et al. ( 2014 ). At that time, the application of hydraulic simulation and or satellite image in preparing flood hazard map was not so prominent. Therefore, the study outputs had question with accuracy. Afterwards, Islam and Sado ( 2000 ) used NOAA-AVHRR images with GIS to develop flood hazard maps for Bangladesh. Tingsanchali and Karim ( 2005 ) studied flood hazard, vulnerability and risk in the southwest region of Bangladesh. However, problem was that they assumed the vulnerability factor to be proportional to population density, which does not truly represent the flood damage data, thus questioning the output of vulnerability as well as risk. For assessing vulnerability, at first the approach should address the elements at risk, and then estimates the damage function. This is the theoretical basis of assessing vulnerability as given by Merz et al. ( 2007 ). Hasan ( 2006 ) followed this theoretical basis for assessing agricultural flood vulnerability in Tarapur union (the smallest rural administrative unit of Bangladesh), Gaibandha district, Bangladesh. Masood and Takeuchi ( 2012a ), Dewan et al. ( 2007 ) and Dewan ( 2013 ) conducted flood hazard and risk assessment for Dhaka, Bangladesh. These studies, particularly the study by Masood and Takeuchi ( 2012a ), indicated to identify elements at risk by following the land use mapping approach, thus improving the output of flood vulnerability.

Recently, we can observe some milestones in flood hazard and vulnerability studies, but not in flood risk study. The application of hydraulic model in flood hazard assessment is becoming popular. We can mention the studies by Afifi et al. ( 2019 ), Zin et al. ( 2018 ), and Tyrna et al. ( 2018 ) that applied different hydraulic models in studying flood hazard. At the same time, land use-based and community-based flood vulnerability study is also getting prioritised. The study by Masood and Takeuchi ( 2012b ) is a comprehensive study showing a clear path of how to conduct flood risk study. The study shows the uses of one-dimensional hydraulic model for hazard assessment and analysis of land use for vulnerability assessment and finally finds out flood risk from hazard and vulnerability. Rakib et al. ( 2017 ) and very recently Hoque et al. ( 2019 ) introduce a new dimension in vulnerability assessment, and this dimension makes the vulnerability assessment become more community focused than before. Their methods include analysing satellite images, a structured questionnaire, criteria mapping, observation and secondary data.

Overall, the studies of flood hazard and vulnerability are good in number as well as they are updated. However, still now flood risk as a concept has not been addressed properly in flood studies. Flood risk is a function of hazard and vulnerability (Alexander 1991 ; Skakun et al. 2014 ). It is the probability of loss due to flood of a given intensity (Alexander 1991 ). The critical point is that while flood hazard is the same for a given area in terms of intensity, the risk could be different depending on a set of conditions and this set of conditions is referred by vulnerability (Crichton 1999 ). Since knowledge on flood risk is must for a planner to plan a disaster resilience society, addressing flood risk properly is a prerequisite, but it has not done yet. This study aims to introduce a new approach of assessing flood risk properly, which successfully addresses this above-mentioned critical issue. The focus of the flood risk of this study is the Baniachong Upazila (Sub-district), one of the flood-affected Upazilas in Bangladesh. Adopting the hydrodynamic behaviour certainly increases the accuracy of flood hazard map (Afifi et al. 2019 ), thereby ensuring better accuracy in flood vulnerability and risk maps. This study applied a 2D hydrodynamic model for the purpose of producing flood hazard map at different return periods of floods in the study site. The hazard maps were assessed under different land use categorizations. The subsequent attempt was to prepare flood vulnerability maps from flood depth–damage functions for cropping land and rural settlements. As a final attempt, the study estimated damage and produced risk maps from vulnerability index and hazard index.

2 Methodology

An integrated and interdisciplinary research approach was followed in this study. Technical assessments were integrated with stakeholders’ views on different aspects of flood hazards and risks. The interdisciplinary nature of the present study warranted the use of a wide range of technical and social research tools and methods. These are hydraulic modelling (with GIS application) of flood inundation, analysis of satellite images to determine different physical elements at risk and using quantitative method (questionnaire survey) to gather information about flood damages to different types of physical risk elements in the study area.

2.1 Description of the Study Area

The principal sources of floods in Bangladesh are the river floods from the major river systems in the monsoon months. A broad strip of land extending beyond the active river floodplains is subjected to this type of flood. The northern and north-eastern trans-boundary hill streams are susceptible to flash floods from the adjacent hills in India in the pre-monsoon months of April and May. Flash floods cause extensive damages to crop and property, particularly in the haor (wetland) areas in the northeast region (Brammer 1999 ). They cause massive damage to dry-season boro (rice variety) rice crop just before or at the time of harvesting. In case of property loss, they cause breaching to embankment and other flood controlling structures, road, railway, bridges, buildings, etc. In this study, one of such flash flood hazard prone areas, the Baniachong Upazila (sub-district) in Habiganj district, was selected for assessments of flood hazard, vulnerability and risk (Fig.  1 ).

Location of Baniachong Upazila and selected gauge stations within the model boundary

Baniachong Upazila with an area of 482.25 km 2 is located in the Agro-ecological Zone—20: Eastern Surma-Kushiyara Floodplain. The mean annual rainfall in the area is about 2659 mm, as compared to the national average of 2300 mm. The rainfall varies considerably within a year, with 79% of rainfall occurring in 5 months from May to September.

The river network close to Baniachong includes Shutki, Old Kushiyara, Shaka, Borak, Shingli, and Bibiyana rivers (Fig.  1 ). These rivers are hydraulically connected with the Kushiyara–Kalni river system which flows down along the north of the sub-basin from northeast towards the southwest and provides a major source of flood water during the monsoon. The major portion of the basin lies outside Bangladesh and the area receives water from Tripura Hills on the south and the run-off from right bank floodplain of the Kushiyara–Kalni. The topography of the floodplain in the study area is generally flat with some depressions located in north and southwest portions of the study area (Elevation map—Fig.  1 ). The area surrounding the CBD (Central Business District) of the Upazila is positioned at higher elevation than distal floodplain of the local rivers (Elevation map—Fig.  1 ).

2.2 Derivation of Design Floods

2.2.1 selection of gauge stations.

A number of water level gauge stations were selected on the main rivers surrounding the study area to be subsequently used in determination of different flood levels corresponding to different return periods and subsequent analysis for floodplain inundation. Figure  1 shows the locations of such gauge stations. The stations selected include Kushiyara River at Sherpur (SW_175.5), Khowai River at Habigang (SW_159), Surma-Meghna at Markuli (SW_270) and Surma-Meghna at Azmiriganj (SW_271).

2.2.2 Frequency Analysis of Water Levels

For study area, frequency analysis of the maximum water level and or discharge during the months of April–May in pre-monsoon season was conducted since it is the flash flood inundation area. The source of the water level data is Bangladesh Water Development Board (BWDB). BWDB provides water level data at every 1-day interval. The time series water level and discharge data at the selected stations were first checked for trends. Frequency analysis was carried out with different probability distributions functions (PDFs). These PDFs are: Two-Parameter Log Normal (LN2), Three-Parameter Log Normal (LN3), Pearson Type III (P3), Log Pearson Type III (LP3) and Gumbel (EV1). To estimate peak discharge for different return periods, some of these five PDFs perform well in some cases. For example, Pumchawsaun ( 2018 ) found Log Pearson Type III (LP3) distribution fit well in case of estimation of peak discharges for 1-in-100 year flood; on the other hand, Khan and Sabbir ( 2018 ) found that Pearson Type III (P3) is the best fitted distribution for overall flood frequency analysis. Since in this present study, it is unknown which distribution fits well for the study area gauge stations; all these five PDFs were compared to get the best fitted distribution. Table  1 shows the equations of all these five distributions.

The PDFs were tested based on the probability plot correlation coefficient (PPCC) (Filliben 1975 ). Goodness-of-fit test based on PPCC is useful for assessing whether a proposed distribution is consistent with the at-site data sample (Stedinger 1993 ). The test uses the correlation coefficient ‘r’ between the ordered observations and the corresponding fitted quantiles, determined by plotting positions for each observation. Cunnane ( 1978 ) plotting position formula was used to obtain the fitted quantiles. The best fit PDFs were selected and subsequently used to determine the design flood level.

2.3 Flood Inundation Mapping

Preparing flood inundation maps based on all primary and secondary data and hydraulic model is the post-stage of derivation of design floods. The use of hydrodynamic models such as  Delft3D, HEC-RAS, MIKE11, SOBEK, HEC-RAS, ISIS, ONDA and FLUCOMP is very common in flood inundation mapping at watershed level. For inundation modelling, Delft3D, a 3D modelling technique developed in the Dutch-based research institute (Deltares 2014 ) was used in this study. Delft3D is a fully integrated computer software suite applied to simulate hydrodynamics, sediment transport, waves, morphological developments, water quality and ecology for fluvial, estuarine and coastal environments. The Delft3D-FLOW, a module of Delft3D, is a hydrodynamic (and transport) simulation program which calculates non-steady flow and transport phenomena resulting from hydraulic and meteorological forcing on a curvilinear, boundary fitted grid or spherical coordinates.

An essential data required for Delft3D hydraulic simulation is the land topographic data. The NASA Shuttle Radar Topographic Mission (SRTM) digital elevation data, available as 1 arc second (approx. 30 m resolution), are very popular land topographic data. This dataset is found to use in many studies (e.g. Patro et al. ( 2009 ), Baugh et al. ( 2013 )) related to flood inundation mapping using flow model. In this study, this SRTM data were used in hydraulic simulation. The DEM data were further processed using ArcGIS to fill in the no-data voids or cells. The C-band radar signal of SRTM dataset is unable to penetrate through vegetation canopy to the bare land surface, resulting in high absolute vertical error in dense forest area (Baugh et al. 2013 ). However, in open land surface this vertical error reduces significantly (Rodriguez et al. 2006 ). Ahead of this problem, in this study, there was an attempt to process the SRTM dataset with vegetation height data to get more accurate output. The vegetation height dataset was collected from Spatial Data Access Tool (SDAT) site. The site provides 1 km Forest Canopy Height globally. However, according to the dataset, canopy height was found zero in the study area. Therefore, regarding the problem with vegetation height, no further processing was carried out with the SRTM dataset.

The processed SRTM data were converted to the sizes required for 728 × 538 grids truncated for the study area using Delft3D-RGFGRID. Important considerations in constructing the computational grids were: (i) the grids must fit as closely as possible to the land–water boundaries of the area to be modelled; (ii) the grids must be orthogonal, i.e. the grid lines must intersect perpendicularly; and (iii) the grid spacing must vary smoothly over the computational region.

Figure  1 shows the model setup for the study area. Two boundary conditions were assigned: one upstream boundary and one downstream boundary. The upstream discharge was considered at location of Sherpur (SW175.5) which is part of the Kushiyara River and the downstream water level was considered at location of Habiganj (SW 159) which is part of the Barak River. The model was simulated for return periods of 2.33, 10, 20, 50 and 100 years. Out of the available time series data at the boundary station, time series were selected such that the peak pre-monsoon water levels are close to the water levels analysed for different return periods at that station. Time step used in simulation for this model is 4 min and the simulation time spanned over 3 months from 1st April to 31st May.

2.4 Flood Damage Vulnerability Analysis

2.4.1 identification of elements at risk.

The first step in vulnerability analysis was to identify the elements at risk in the study area. The elements at risk are defined as the level of exposure with reference to agricultural fields, buildings/infrastructure, population, economic activities, public services and utilities, etc., which can be impacted by the flood hazard (Dewan 2013 ). In this study, elements of risk were identified by analysing satellite images in the GIS environment and hence obtaining land use map, followed by overlying the elements onto flood inundation maps. Field observations and interviews were conducted to verify the elements identified.

Land use/land cover (LULC) dataset was generated from the digital image classification of Landsat, ETM + satellite images of 2011, downloaded from Global Land Cover Facility ( https://glovis.usgs.gov/ ). Among various image classification techniques, the maximum likelihood algorithm is shown to produce useful outcome in deriving LULC (Dewan and Yamaguchi 2009 ; Jia 2019 ). Therefore, in this study supervised classification of maximum likelihood algorithm was applied to classify Landsat images into discrete land LULC categories. An overall workflow in preparing LULC map is shown in Fig.  2 . The classification was performed on false colour composition of bands 4, 3 and 2 into following land use and land cover classes: cropping land, rural settlement, urban settlement, water bodies and bare land. Information collection during field survey as ground-truthing point was used to assess the accuracy of classification. The elements at risk identified for the study areas include cropping land and rural settlements (i.e. homesteads), because other land cover classes are not important from flood risk point of view. It is noted here that image classification did not yield roads as one land use classification. Finally, inundation layers were overlaid on land use layer to obtain the overlaid zones. From the ArcGIS overlay analysis, different sort of inundation statistics was generated.

Workflow showing land use classification

2.4.2 Assessment of Flood Damage Functions

The quantification of vulnerability depends on the susceptibility of ‘elements at risk’. It can be termed as the degree of loss to a given element at a given severity level. It is usually expressed on a scale 0 (no damage) to 1 (total loss) unit. The present study considers ‘depth of inundation’ as the main parameter for assessing flood damage functions for croplands and rural settlements. The study further considers the direct economic damages of floods. Considering depth as the flood damage parameter, depth–damage relationships (alternatively called loss functions or vulnerability functions) were developed for different elements at risk: crops and settlements. Depth–damage relationship presents information on the relationship of flood damage of a certain element to a certain depth of flooding (or stage) (Smith 1994 ).

In this study, for developing depth–damage relationship for crop, the flood damage data were collected from different secondary literature and organizations, and extensive interviews with the local people were conducted as part of the questionnaire survey. A total of 120 local people including farmers, fishermen, and small businessman from the study site were interviewed as household basis. A questionnaire survey was preferred for this interview session as it provides insight into the information of inundation depth and associated flood damages. The survey was conducted following a random sampling method to select respondents for the household interviews. The structured questionnaire was first pre-tested in 15 randomly selected households. Then, modifications were made before the actual interviews of the sampled households. Additionally, the questionnaire was administered to respondents who (i) were aged 20 years and above, (ii) had lived in the respective area for at least 15 years, and (iii) were main decision makers in the household, and/or, in the absence of a family head, it was made with appropriate representative and knowledgeable member of the household. The questionnaire survey covered the local perceptions on crop and settlement damages associated with different remarkable flood events such as 1988, 1998, 2004 and 2007 as well as collected information on damage corresponding inundation depths. Damage was assessed in terms of the amount of money (presented as percentage of the total production value) necessary to recover the original production. Based on this flood depth–damage information from questionnaire survey, depth–damage curve was developed.

For developing the depth–damage relationship for settlement, a valuation survey was conducted for the settlement vulnerability assessment. Following the study by Islam ( 2005 ), settlements were classified into four types such as brick floor–brick wall (BB), brick floor–CI sheet wall (BC), mud floor–CI sheet wall (MC), and mud floor–mud wall (MM). For the selected properties, the survey quantified the damage of all items due to flood and their current value based on type, quality and degree of wear. This included information on the height above the floor of each item or the height taken as standard from house to house. The information for all samples of each element class was then averaged and stage-damage curves were constructed.

2.5 Flood Risk Assessment

As risk is a combination of hazard, vulnerability and exposure (i.e. elements at risk) (Skakun et al. 2014 ), in the final step of risk assessment, the expected damage of the risk element was estimated first by combining replacement values assessed for the elements and then following the stage-damage function. The following equations were followed to estimate expected damage.

where D is total direct property damage per cell of the raster map, ‘vul’ is the vulnerability value per cell which is the function of Depth (DP) in meter and duration (DR) of inundated land in days, A is the area of each cell in sq.m and P is the property value in monetary terms of each cell. Here, ED is the expected damage and T is the return period of flood.

Property value data per hectare of each land use class were collected from the field survey. Data on average unit prices of houses and cropping land under the present circumstances were collected from the field survey. After that, a land use-based raster map showing the monetary value for each land parcel was prepared (Economic Value in Fig.  3 ). Direct damages to properties of economic units were classified as settlement and agricultural damages (Vulnerability in Fig.  3 ). Then, the expected damage value was classified into several defined classes using GIS environment (Expected Damage in Fig.  3 ). The single output map algebra in Fig.  3 was the product of direct property damage ( D ) divided by return period pf flood (T). The conceptual model for entire flood risk mapping is shown in Fig.  3 .

Conceptual model for flood risk assessment

3 Results and Discussion

3.1 frequency analysis of water levels.

The fitted PDFs and the corresponding values of PPCC for annual maximum water levels of the selected gauge stations and for maximum discharge for Kushiyara River at Sherpur (SW_175.5) station are shown in Tables  2 , 3 , 4 , 5 , and 6 . The probability plots along with 90% confidence interval for the annual maximum water levels of the selected gauge stations are shown in Fig.  4 . It is seen that the observed values fall well within the 90% confidence interval of the fitted distributions for annual maximum water level.

Probability plot along with 90% confidence interval of the fitted distributions to the pre-monson peak water level data of different gauge stations in Baniachong Upazila

3.2 Model Calibration and Validation

After simulating the hydrodynamic model Delft3D, the first step was to calibrate and validate the model’s output with observed data. Water level (WL) data for the month April to May 2007 (pre-monsoon) of Markuli (SW 270) station were used for calibration purpose. The selected Markuli (SW_270) station belongs to the Surma-Meghna River system (Fig.  1 ). The calibrated parameter was the Manning’s roughness coefficient ‘n’ in the river. Similar to the study by Dutta and Nakayama ( 2009 ), land use types were the basis for estimating the roughness coefficients for rivers and surface in this present study. From the calibration, a close agreement between the observed and calculated water level (Fig.  5 ) using the roughness coefficients between 0.019 and 0.023 was found.

Water level calibration of the model at Markuli station (SW 270)

After calibration, the model was validated against the water levels (WL) for the month April to May 2007 of Azmiriganj (SW 271) station at Surma-Meghna river. The validation shows that the observed and computed water levels are close (Fig.  6 ). The computed water level at this station was found to vary within − 0.17 and the coefficient of determination ( R 2 ) is 0.72. Further validation was carried out between the observed flood extent of 1998, a 100-year flood event (Islam and Chowdhury 2002 ), and the modelled 100-year flood extent (Fig.  7 ). The extent of 1998 flood was maximum from 27th July 1998 to 07th September 1998 in the study site as per BWDB ( 2010 ). RADARSAT image covering the 1998 inundation extent was found available for 26th August, which is within the specified range of maximum flood extent. Therefore, this RADARSAT image was used for delineating the observed inundation extent of 1998 flood. It was found 76.5% accuracy between the modelled and the observed inundation extents when a GIS overlay operation was performed between these two extents.

Water level validation of the model at Azmiriganj station (SW 271)

Map showing 100-year flood inundation computed from modelled scenario (left) and 26 August 1998 flood inundation from observed scenario

3.3 Inundation Maps

Simulation by Delft3D model yielded floodplain inundation depths at different return periods, as presented in Fig.  8 and Table  7 . It was found that overall with the increase in return period the inundated area increases substantially for the flood class of “Low (0–2 m)” and “Medium (2–4 m)”. However, exception is 20-year return period of flood, where inundated area for the flood class of “Low (0–2 m)” decreased as compared to the flood class of “Low” at 10-year return period. Noticeably, at 2.33-year flood event, only the north side of the study area was inundated, but with greater return period of flood the western and the southern sides of the study area were inundated gradually. There was no inundated area for “High (4–6 m)” class of flood at 2.33-year return period; however, at greater reoccurrence of flood (greater than 10-year) inundated area of “High” class of flood was present with slight extent (~ 1 km 2 ). The percentage area of inundation increased from 28.77 to 80.28% corresponding to 2.33-year return period to 100-year return period, respectively, for flood class low. Whereas for medium and high class floods, the area of inundation increased from 0.31 to 10.23% and 0 to 0.28% for return period 2.33 years to 100 years, respectively.

Inundation depth (flood hazard map) for different return periods in Baniachong Upazila

At low reoccurrence interval of flood, the major river systems are not always seen to play major role in flooding the adjacent floodplains by their overbank flows. Rather, floodplains are inundated from the flows coming from local floodplain channels connected with the major river systems (Jeb and Aggarwal 2008 ; Luo et al. 2018 ; Tanaka et al. 2017 ). This is why the distribution of floodplain inundation can be sporadic at low reoccurrence interval of flood. However, at later stages of flood as water levels continue to rise, floodplains get closer to major river and meet flows directly coming from the river (Fantin-Cruz et al. 2011 ; Karim et al. 2016 ; Yin et al. 2013 ; Zin et al. 2018 ). Then, a vast expanse of the floodplain is inundated. The pattern of inundation in the study site showed similar behaviour at different return periods of flood. Except few areas, the whole study site was inundated (Fig.  8 ) by the overbank flows coming from the major rivers (Fig.  1 ) (the Kushiyara, the Khowai, the Surma-Meghna and the Barak) at recurrence interval of flood greater than 20. At relatively low recurrence intervals of flood, a small portion of the study site, northern portion mainly, was inundated possibly by local floodplain channels only. The floods with a relatively low return period have a large influence on the annual risk. At the same time as these floods may cause relatively low economic damage per event, their relatively frequent occurrence means that they should be fully considered in flood risk assessments (Ward et al. 2011 ).

The inundation extent in the study area simulated by Delft3D model is comparable to other studies. The percentage of flooded area in Baniachong Upazila was 86.63 as on June 13, 1998 (BWDB 2010 ). Study conducted by Bhuiyan et al. ( 2010 ) termed the 1998 flood is a return period of 75 to 100 years. In this study, for 100-year return period, 80.28% (399.34 km 2 ) area was found under flooding (Table  7 ), which is quite close to the BWDB study.

3.4 Inundation of Different Land Use Categories

Supervised classification of LANDSAT image with ArcGIS yielded different land cover existing in Baniachong. The land cover map was assessed against Google Earth image. The assessment was 30 m apart sampling basis, since the LANDSAT image used in this study is approximately 30 m in resolution. Bai et al. ( 2015 ) also used Google Earth images when assessed land use map of China. Overall accuracy in the Bai et al. ( 2015 ) study varies from 48.6 to 68.9%. In the present study, the assessment shows 70%, 100%, 60%, 62% and 60% accuracy in water bodies, urban settlement, rural settlement, cropping land and bare land categories, respectively, in the derived land cover map.

The land use map of Baniachong is shown in Fig.  9 . About ~ 4%, ~ 18%, ~ 27%, ~ 37% and ~ 15% are covered by water bodies, urban settlement, rural settlement, cropping land and bare land, respectively. This distribution of land use classes is representative to a typical rural area of Bangladesh (e.g. Khan et al. ( 2015 ), Parvin et al. ( 2017 )).

Land use map of Baniachong Upazila

Figure  10 presents the percentage of inundation area for each land use class at different return periods of flood. It is found from Fig.  10 that the affected area increases with the increase of return period and flood depth for all land use classes. It is noticeable that, with the increase in return periods from 2.33 to 100 inundated areas become more than tripled for land use classes rural settlement (~ 37 to ~ 126 km 2 ), urban settlement (~ 13 to ~ 63 km 2 ) and bare land (~ 14 to ~ 57 km 2 ), and more than doubled for land use class cropping land (~ 76 to ~ 188 km 2 ). The percentage inundation of urban settlement (~ 16 to ~ 85) is higher than that of rural settlement (~ 15 to ~ 69) with the increase in return period. Water bodies were inundated much more (~ 29% at 2.33-year flood and ~ 90% at 100-year flood) than that of any other classes of land use. It reflects the loss of capture fisheries during flooding. The rising trend of inundated area for cropping land, which is the most dominant land use type, decreases with the increase of return periods. Noticeably, in case of higher reoccurrence interval of flood (e.g. 50 and 10-year floods), inundated area for cropping land remains the same with the increase of return period.

Percent of inundation area for each land use class at different return periods (years)

The settlement areas (both urban and rural) in the study site are slightly elevated locally, as like as other settlement areas in Bangladesh (Choudhury 1973 ). This is why these areas usually do not receive flood flow from major rivers nearby or even from local floodplain channels at low reoccurrence interval of flood. Furthermore, man-made structures, such as road network, obstruct lateral and longitudinal connectivity of flood water fluxes (Kumar et al. 2014 ), thereby reducing the chance of inundation in the settlement areas of Baniachong Upazila. As a result, only a negligible portion of the settlement areas (~ 28% for rural settlement and ~ 16% for urban settlement at 2.33-year flood) were inundated at low reoccurrence interval of flood as found from the simulation. However, at greater reoccurring interval of flood, the settlement areas received flood water as the flood flows defeat the settlement elevation and or overtop the man-made structures. This led to abrupt inundation of the settlement areas, thereby increasing the inundated area in percentage (~ 28% at 2.33-year flood to ~ 94% at 100-year flood) (Fig.  10 ). Cropping or agriculture land areas, which are typically as depressions or low elevated zone in active and older floodplain, often receive flood water from major rivers as well as from local floodplain channels (Charlton 2008 ). The cropping land area in Baniachong Upazila most probably has similar characteristics in terms of flood water connectivity with the major rivers and the local floodplain channels. Therefore, most of the area of cropping land was inundated at low reoccurrence interval of flood (~ 40% and ~ 80% at 2.33 and 10-year floods, respectively) and unlike settlement areas, the inundated area did not increase abruptly and even did not change at greater reoccurrence interval of flood (from 50- year to 100-year flood) (Fig.  10 ).

3.5 Floodplain Damage Vulnerability

3.5.1 damage function and damage vulnerability mapping.

Figure  11 shows the depth–damage curves for two elements of risks: cropping lands and rural settlements for the study site. Depth–damage functions for these two elements were constructed with the help of hazard maps shown in Fig.  8 . It is noted here that the damage function shown here for rural settlement refers to an average for four dominant types of settlements usually found in the study site (as discussed in Sect.  2.4.2 ). This damage function was used to represent the physical vulnerability of the rural settlements since it was not possible to distinguish the four different types either in the satellite image processing or through field survey.

Flood damage vulnerability (depth–damage function) of cropping land and rural settlement

Using the hazard map (Fig.  8 ) and the stage-damage curve (Fig.  11 ), crops vulnerability maps for different return periods of flood were constructed, as shown in Fig.  12 . In the crop vulnerability mapping, the flood depths were divided into five scales (0–0.5 m, 0.5–1 m, 1–1.5 m, 1.5–2 m and 2 m and above) and their respective vulnerability is: very low vulnerable (0–0.25), low vulnerable (0.25–0.45), medium high vulnerable (0.45–0.65), high vulnerable (0.65–0.84) and very high vulnerable (0.84–1) for different return periods of flood.

Vulnerability rank for cropping land at different return periods of flood

From Fig.  12 , it is found that crop vulnerability increases with the increase in return period. Almost 20% of the total cropping land area is “high” and or “very high” vulnerable to 100-year flood. These areas are close to the rivers (Fig.  12 ), and further generally laying at low elevations (Elevation map—Fig.  1 ). On the other hand, ~ 42% of the total cropping land area is “low” to “medium high” vulnerable to 100-year flood. Most of these areas tended to be further away from the high drainage density areas. Significantly, the results in Fig.  12 depict the fact that the cropping land in northern portion of the study site is much more vulnerable to flood than any other area of the study site. This is due to the fact that the northern portion is very close to the Suriya-Kalakhai River system (Fig.  12 ), one of the major rivers in the study site. Furthermore, the area is a depression zone identified in the elevation map in Fig.  1 . Consequently, the extent of flood damage would be higher in norther portion than any other portion of the study site. Note that, this proposition is true for same flood, in terms of intensity and exceedance probability. However, one might argue with different varieties of crop as crop vulnerability can differ from one variety to another variety (Cutter 1996 ). This is probably a scope of further study in future.

Rural settlement vulnerability maps for different return periods of flood were constructed, as shown in Fig.  13 . In the rural settlement vulnerability map, the flood depths were divided into six scales (0–0.5 m, 0.5–1 m, 1–1.5 m, 1.5–2 m, 2–2.5 m and 2.5 m and above) and their respective vulnerability is: very low vulnerable (0–0.15), low vulnerable (0.15–0.35), medium low vulnerable (0.35–0.6), medium high vulnerable (0.6–0.75), high vulnerable (0.75–0.9) and very high vulnerable (0.9–1) for different return periods.

Vulnerability rank for rural settlement at different return periods of flood

The result of vulnerability map for rural settlement showing in Fig.  13 depicts that rural settlement vulnerability increases with the increase in return period. Overall, irrespective of any class of vulnerability, ~ 28% of the total rural settlement area is vulnerable to flood at 2.33-year return period. This percentage becomes ~ 95% at 100-year flood. Now, if looking on the basis of vulnerability class, only 0.2% of the total rural settlement area is “high” and or “very high” vulnerable to flood at 2.33-year return period. However, at 100-year flood this percentage increases to ~ 8. This increasing trend is probably due to the nearby Kalni River (Fig.  13 ). Noticeably, rural settlement area with “low” and or “very low” vulnerable to flood increases sharply with the increase in return period (~ 15% of the total rural settlement area at 2.33-year flood increase to ~ 30% of the total rural settlement area at 100-year flood). These areas where rural settlement vulnerability with “low” and or “very low” increases are tended to be either close to the Suti River and the Barak River (Fig.  13 ) or laying at relatively low elevations (Elevation map—Fig.  1 ). As a whole, distance from river to settlement determines the settlement vulnerability in the study site. However, type of settlement is obviously a factor in this regard, but it is out of scope in the present study.

3.5.2 Damage estimation and risk mapping

The expected damage of the inundated land use types was estimated using equation outlined in Sect.  2.5 . The value of P (property value) was found to be Tk. 9.4 (Tk. 2820 per cell) for agriculture and Tk. 590 for settlement (Tk. 177,000 per cell). Thus, raster-based damage maps for various return of floods were produced.

Figure  14 shows the expected damage or risk map for cropping land at different return periods of flood. Figure  15 presents the percentage of cropping land area with different levels of risk at different return periods of flood. From Figs.  14 and 15 , it is found that overall the cropping land area with different classes of flood risk increases with the increase in return period. However, cropping land areas with “Low” and “High” flood risk decrease (~ 30 km 2 to ~ 28 km 2 for “Low” and ~ 28 km 2 to ~ 12 km 2 for “High”) with the increase in return period from 10 to 100-years and 50 to 100-years, respectively (Fig.  14 ). The cropping land in southern portion of the study area is not under risk at 2.33-year flood, but in northern portion it is always under risk at all level of floods (Fig.  14 ).

Expected damage or risk map for cropping land at different return periods of flood

Percent of cropping land area with different levels of risk at different return periods of flood

The reason why cropping land areas with “Low” and “High” flood risk decrease with the increase in return period is probably because these areas are shifted to either risk class of “Medium” or “Very high” when affected by greater reoccurrence interval of flood. Overall, existing topography and river-channel network performing as vulnerability element and flood depth as hazard element determine the spatial distribution of different levels of flood risk for the cropping land in the study site. The northern portion of the study area has depression (Elevation map—Fig.  1 ), and this is probably the main reason for which the area is under flood risk at all level of floods. Furthermore, the Kalni River at north is also responsible for the area to be flooded at all level of floods. The drainage density in southern portion of the study area is relatively higher (Fig.  14 ), thus increasing the flood risk level for cropping land in respective area.

Figure  16 shows the risk maps for rural settlement at different return periods of flood. Figure  17 presents the percentage of rural settlement area with different levels of risk at different return periods of flood. Figures  16 and 17 show that except the area covered by the risk classes of “Low” and “Medium high” all other classes increase with the increase in return period. Significantly, the area covered by the risk class of “Very low” increases much more (~ 14 km 2 at 2.33-year flood to ~ 67 km 2 at 100-year flood) than any other classes. The rural settlement areas located south and south-east of the Suti River (Fig.  16 ) are not at risk to 2.33-year flood. However, at greater reoccurrence interval of floods, these areas, particularly the areas close to the Suti River, fall under the risk classes from “Medium low” to “Very high”. The reason could be the existence of intricated network of river-channels close to the area as shown in Fig.  16 .

Expected damage or risk map for settlement at different return periods of flood

Percent of rural settlement area with different levels of risk at different return periods of flood

Overall, the study finds that areas with different levels of flood risk do not correspond to the areas of inundation at different return periods of flood. While the areas of inundation increase with increase in return period of flood, the areas with different levels of flood risk are determined by depth of inundation and depth–damage function (i.e. vulnerability index).

4 Conclusions

Baniachong Upazila represents a flash flood area where Boro rice is the dominant crop, and this variety of crop is a very important element for estimating risk. Area of inundation depth increases substantially with increasing return period, which has a considerable impact on the area of cropland and also the area of settlements. It was found that cropland is highly vulnerable at 2.8-m depth, while settlement is highly vulnerable above 3-m depth.

Traditionally, hydrologic/hydraulic models are commonly used to study or delineate the potential areas of flood hazard at given recurrence interval of flood. Determining the flood hazard using one of the popular hydraulic models, and then delineate the flood vulnerable and risk areas as carried out in this study for Baniachong Upazila is important for decision makers, planner and overall management activities. Importantly, this study shows an effective approach of integrating GIS, hydraulic model and field survey in the study of flood risk assessment, and this approach successfully assesses flood risk in the study site, where risk as a concept has been placed in terms of theoretical framework. Furthermore, the study showing approach to flood risk assessment is relatively inexpensive and easy to manage and more significantly allows interactive use by flood managers for continuing improvement.

Nonetheless, the study has a number of limitations mainly due to resource and time constraints. Damage due to floods can depend on a number of factors, including depth of flood inundation, duration of flooding, flow velocity, timing of occurrence, rate of rise of flood, etc. However, the study did not consider any other potential factor except ‘depth of inundation’ as the parameter for assessing flood damage functions. While flow velocity is typically an important damage parameter in such flash flood area, not considering it may be justified, since the area is much inland corresponding to a higher order catchment and the fact that the effect of velocity is maximum in the hilly, the border areas, which gradually diminishes with the increase in the order of the catchment. However, velocity is one important parameter while assessing flood damage due to storm surges and future study should be undertaken considering this parameter.

Another limitation is that only the direct economic damages of floods has been considered, while some studies (i.e. Smith ( 1994 )) indicated that indirect flood damage (with multiplier effect) may assume a significant proportion of the total flood damage. While vulnerability due to flood hazards encompasses physical, social, economic and environmental dimensions, only the physical vulnerability aspects have been considered in the present study because of resource limitation and lack of time to carry out the investigation.

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Zin WW, Kawasaki A, Takeuchi W, San ZMLT, Htun KZ, Aye TH, Win S (2018) Flood Hazard Assessment of Bago River Basin. Myanmar J Disaster Res 13:14–21

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Acknowledgements

The study was financially supported by the Climate Change Trust Fund of Climate Change Cell under Ministry of Forestry and Environment (MoEF) of Government of Bangladesh. It was being implemented by Climate Change Study Cell housed at Institute of Water and Flood Management (IWFM), Bangladesh University of Engineering and Technology (BUET). The authors of the study sincerely acknowledge the help from Dr Ashraf Dewan, Senior Lecturer, School of Earth and Planetary Sciences (EPS) for providing a general outline to prepare this study. He is also acknowledged for providing the RADARSAT image of 1998 flood event, which was used in this study for validation purpose of the hydraulic model’s result.

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School of Geography, University of Melbourne, Melbourne, Australia

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Sylhet Agricultural University, Sylhet, Bangladesh

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Baky, M.A.A., Islam, M. & Paul, S. Flood Hazard, Vulnerability and Risk Assessment for Different Land Use Classes Using a Flow Model. Earth Syst Environ 4 , 225–244 (2020). https://doi.org/10.1007/s41748-019-00141-w

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Received : 14 August 2019

Accepted : 20 November 2019

Published : 05 December 2019

Issue Date : March 2020

DOI : https://doi.org/10.1007/s41748-019-00141-w

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Addressing Worldwide Flood Concerns: Empowering Local Communities

Denise Corsel

Over the last 25 years, the world has seen a rise in the frequency of natural disasters in rich and poor countries alike. Today, more people than ever are at risk from natural hazards, with those in developing countries particularly at risk. This essay series is intended to explore measures that have been taken, and could be taken, in order to improve responses to the threat or occurrence of natural disasters in the MENA and Indo-Pacific regions. Read  more ...  

Floods have become a growing concern throughout the world. [1] Fueling this concern is the prediction that climate change will increase the intensity and severity of flooding. [2] There are also growing concerns that climate change will dramatically increase the health risks associated with contaminated water and dangerous substances that are released during floods. [3] These concerns need to be addressed in order to reduce the negative impact of floods upon communities worldwide.

Coping with floods is a major challenge for many communities, especially those in developing nations, which generally have to manage the responses to and recovery from them mostly on their own. Governments, NGOs and other organizations provide aid during a natural disaster when, where and how they can. However, their extent of their contributions sometimes fail to meet the needs of local communities, especially immediately following the disaster but also in the longer term, due to their limited financial capabilities, inadequate access to affected areas, lack of awareness or political constraints under which they operate.

This essay focuses on the role of local communities during the recovery stage from floods. By drawing on a case study of rural communities in Laos, [4] the essay highlights the potential benefits of equipping local communities with long-term practices that will assist them in recovery efforts. The essay concludes with a discussion of the lessons and insights gained from this case and that they could be applied in other countries to improve flood resiliency.

The Importance of a Community-Centered Approach

This essay discusses floods from the perspective of long-term recovery since the latter contributes to resiliency, which is defined as “the ability to recover readily.” [5] The recovery stage—encompassing the process and outcome—is crucial because it covers everything that is required for the affected community to return to conditions of normality. [6] Floods are almost impossible to prevent and the scale of adverse consequences from floods is exceedingly difficult to gauge. Therefore, mitigating the consequences of floods is often quite challenging, especially in rural villages in developing countries, where technology and finances are in short supply. This overall magnifies the importance of the recovery stage.

Local communities are directly affected by floods and thus are the primary risk-bearers in such situations. They are the first on the scene and generally carry out the initial response. It is thus important to focus particularly on local communities during their recovery. Floods can inflict enormous damage, [7] especially upon those who are the most vulnerable community members. The damage affects property, finances, job security, emotional and health status, and livelihoods. Therefore, the community affected has an investment and a strong motive to recover and to return to normal life as quickly as possible. Compared to others, such as aid organizations, supporters and governments, the community itself will prioritize the recovery process the most. Therefore, a community-centered approach to improve flood resiliency is recommended. The Sendai Framework for Disaster Risk Reduction [8] supports this by emphasizing that there should be a people-centered approach when preventing disaster risk. To do so, during the recovery stage of a flood it is important for people to be both reflective and pro-active so that they can improve the management of future flooding.

Another reason why a community-centered approach is recommended is because with the increase of natural disasters throughout the world, [9] aid response will not be enough on its own. Resilient development [10] is, therefore, more important now than ever before. Developing the community to be resilient will not only enhance the efficiency of the recovery, but will assist with building a stronger system that can better manage all types of risks while improving the chances of maintaining the progress made by the community. Overall it will strengthen the current links between aid organizations and the communities’ development work, which allows for a lasting change. [11]

A community-centered approach can be highly efficient since communities know and understand their own situations best. Some would argue that experts possess greater expertise, theoretical knowledge and specific skills than the communities they seek to assist. Nonetheless, the local public has more everyday knowledge regarding their own surroundings and how their community members are likely to respond to certain recovery actions, which may be crucial to recover efficiently. Additionally, when preparing for a potential flood disaster, the community is the only party that has a clear emotional investment regarding the potential impacts and risks. In any event, it is imperative that all relevant stakeholders are included and participate to have a successful recovery process and outcome. [12] Community participation will enable more effective and long-term flood practices, improve the overall flood management process in place and allow for safer and quicker decisions to be made.

Helping to equip local communities, including their most vulnerable members, with recovery practices will enable them in the long-term to augment their own resilience to floods, which will be especially useful in case the prediction [13] that climate change will produce more intense and severe flooding is correct. As illustrated in the case of Laos’ rural communities, local communities, specifically those that are prone to flooding, tend to already have several recovery practices in place that could, and should be bolstered through the contributions of experts, government authorities and aid.

Recovery Practices in Laos

While numerous flood recovery practices are used throughout the world, local communities in Laos have their own practices, especially since they often experience flooding due to the annual rainy season. Flooding is Laos’ main hazard [14] that affects communities all across the county and often develops into a disaster. [15] Therefore, Laos’ coping practices have developed over many generations. They include traditional practices such as constructing houses on stilts; setting up community banks of rice; using traditional medicines; seeking shelter in temples and/or schools; creating dug-out drainage systems for paddy fields; and removing water from houses with baskets. These practices do indeed help with recovery, though they are predominantly needs-based coping strategies. However, NGOs and United Nations staff are teaching and/or sharing with rural communities other, more advanced flood resilience practices, such as using pumps to remove water; creating official village disaster committees and disaster preparedness plans; employing sturdier home building and repair techniques (e.g. using concrete or stronger wood); and implementing food and drinking storage systems.

In Laos, the management of flooding, which is challenging due to unpredictable flash floods, is primarily conducted at local levels and appears to be effective due to enhanced focus on villages’ own disaster management committees. Owing to the country’s financial situation, [16] flood management is mostly conducted by the individual village, which has its own village chief and elder. Often when a flood occurs, it is not possible for outsiders, including government officials, to enter/reach the villages affected. Therefore, it is important to focus particularly on local communities’ own coping mechanisms during recovery. In such a situation, Laos’ citizens currently manage and work together as a community to manage floods. So far, this has been working satisfactorily. However, with the building of houses in floodplains, logging trees and signs that changing climate is increasing the severity of floods and droughts, [17] existing local coping mechanisms might not be enough. Yet, whether their current practices are adequate to meet these immediate challenges or not, equipping Laos’ citizens with additional recovery practices would be highly beneficial, as it would allow the communities to better manage the (current and future) physical, emotional and secondary damage created by flooding disasters by strengthening their resilience. Additionally, it would allow them to handle the floods better in the long-term, especially if flooding worsens.

Laos’ villagers could learn from other recovery practices used in other countries. For instance, in Khammouane Province (Laos) the main concern during the recovery stage is health since floods spread disease and drinking and washing water become contaminated. This issue could be mitigated by chemically treating the water, as is done in Tanzania [18] or by using water purification tablets, as is done in Bangladesh. [19] Furthermore, another recovery practice that the majority of communities throughout Laos would benefit from would be the introduction of a rice variety that can withstand flooding because currently during floods the loss of rice, the main source of their livelihood, [20] is reducing their capability to recover. This practice has been effective in India, Bangladesh and Nepal, [21] and research is being conducted on how this would work in Laos. [22] There are many other practices that may be helpful, such as in Thailand, where communities are involved with hazard mapping to enhance education, [23] and in Vietnam, where they use schools to hold flood safety campaigns. [24] The idea that building on current practices while introducing new ones to enhance communities’ resilience is gathering momentum.

Nevertheless, it is important that communities are supported in selecting the most beneficial and realistic recovery practices. Additionally, it is crucial that the practices are manageable and accessible by the communities over the long term, thereby ensuring that they are sustainable. As a result, the communities would be empowered and capable of recovering from floods better and quicker, as well as potentially recovering from other natural disasters because some of these practices are transferable.

Some of Laos’ citizens may be content with the way floods are currently managed; however, most are open to learning and to trying out new practices and/or enhancing their current recovery practices. Moreover, villages, such as those in Laos, where residents have learned to cope with disasters on their own and thus, a community-centered approach is already in place, are likely to be more open to strengthening and building on their current approach than to acceding to outsiders’ management of the recovery stage. In fact, Laos’ government, in apparent recognition of this, supports village disaster management committees. Several aid organizations, including the Global Facility for Disaster Reduction and Recovery [25] and the United Nations also promote sustainable assistance to ensure that long-term resilience is strengthened in such a manner that the country and its communities will be better able to manage disasters and ‘build back better’ [26] without them.

Equipping local communities with long-term recovery practices, some of which may be learned from other countries and adapted to country-specific circumstances could contribute to more effective disaster recovery, a better flood management process, and safer and quicker decisions. The main lesson learned from the case study of rural communities in Laos is that in countries where aid is not always readily accessible and where a community-centered management approach has been forming over the years, it is important to focus on and enhance the community-centered approach during the flood recovery stage. Given that the incidence of flooding has increased and is predicted to worsen in countries, including Laos, [27] special attention should be devoted to strengthening long-term local recovery practices, which is part of resilient development. In particular, as also illustrated by this case study, it is crucial to consider sustainability when improving flood resilience at local levels.

Undeniably government agencies and aid organizations play a vital role in disaster management. Nevertheless, they should focus on enhancing the communities’ resilient development so that, in the future, communities can manage floods better on their own and conduct the recovery process with greater efficiency. Particularly during the recovery stage, the risk-bearers should be principally in charge of managing their situation, as it is they who know best what is required to return the community to a state of ‘normality’ as quickly as possible. Where possible, the risk-bearers should be supported in their efforts to guide ‘building back better’ initiatives. [28]  In sum, attention should be focused more sharply upon, and more support and resources should be invested in local communities to improve their flood resilience by enhancing their current recovery practices and introducing new ones.

[1] Dawei Han, Flood Risk Assessment and Management (Sharjah: Bentham Science Publishers, 2011) 1.

[2] Duncan Geere, “Global Flooding Risk Could Triple by 2030,” Wired , March 5, 2015, accessed April 15, 2016, http://www.wired.co.uk/news/archive/2015-03/05/flooding-predictions-2030 ; and Tianyi Luo ,  Andrew Maddocks ,  Charles Iceland , Philip Ward and Hessel Winsemius, “World’s 15 Countries with the Most People Exposed to River Floods,” World Resources Institute , March 5, 2015, accessed April 15, 2016, http://www.wri.org/blog/2015/03/world%E2%80%99s-15-countries-most-peopl… .

[3] Roger Few and Franziska Matthies, eds ., Flood Hazards & Health: Responding to Present and Future Risks (London: Earthscan, 2006); and National Geographic, “Floods,” National Geographic , 2015, accessed June 26, 2015, http://environment.nationalgeographic.com/environment/natural-disasters… .

[4] Laos, located in South-East Asia, is officially known as Lao PDR, which is short for Lao People’s Democratic Republic.

[5] Michael Pitt, Learning Lessons from the 2007 Floods: An Independent Review by Sir Michael Pitt (London: Cabinet Office, 2008) 349, accessed April 15, 2016, http://webarchive.nationalarchives.gov.uk/20100807034701/http:/archive… .

[6] Home Office, Dealing with Disaster (London: Cabinet Office, 1998), accessed April 15, 2016, http://webarchive.nationalarchives.gov.uk/20050523205851/http:/ukresili… .

[7] Roger Few and Franziska Matthies, eds ., Flood Hazards & Health: Responding to Present and Future Risks (London: Earthscan, 2006).

[8]  United Nations Office for Disaster Risk Reduction (U.N.I.S.D.R.), Sendai Framework for Disaster Risk Reduction 2015-2030  (2015) 10, accessed April 15, 2016, http://www.unisdr.org/files/43291_sendaiframeworkfordrren.pdf .

[9] International Federation of Red Cross and Red Crescent Societies, Introduction to the Guidelines for the Domestic Facilitation and Regulation of International Disaster Relief and Initial Recovery Assistance (Geneva: International Federation of Red Cross and Red Crescent Societies, 2011) 3.

[10]  Natalia Adler, “Resilient Development Means Better Preparing Children, Families and Communities for Shocks, Making Sure They Can Better Withstand Them, and Helping Them to Recover Quickly,”  U.N.I.C.E.F. Technical Note: Resilient Development (2016) 3.

[12] Upala Banerjee, “Adopting Rights-Based Programming Strategies Towards Developing Capacities for Accessing Sustainable Water and Sanitation Facilities: The NAM SAAT/Sida/UNICEF Partnership in Luang Prabang Province in Laos - A Case Study” (U.N.D.P., 2005) 249, accessed May 15, 2016,  http://www.unescobkk.org/fileadmin/user_upload/appeal/LLP/LLP_Documenta… .

[13] Duncan Geere, “Global Flooding Risk Could Triple by 2030,” Wired , March 5, 2015, accessed April 15, 2016, http://www.wired.co.uk/news/archive/2015-03/05/flooding-predictions-2030 .

[14]  United Nations Office for Disaster Risk Reduction (U.N.I.S.D.R.), Country Assessment Report for Lao PDR: Strengthening of Hydrometeorology Services in Southeast Asia   (2013), accessed April 15, 2016, http://www.unisdr.org/files/33988_countryassessmentreportlaopdr[1].pdf .

[15] Saysoth Keoduangsine, Robert Goodwin and Paul Gardner-Stephen, “A Study of an SMS-Based Flood Warning System for Flood Risk Areas in Laos,” International Journal of Future Computer and Communication  3 (2014): 182-186, accessed May 15, 2016, http://www.ijfcc.org/papers/292-M052.pdf .

[16] The World Bank, “Lao PDR Overview,” last modified April 2016, http://www.worldbank.org/en/country/lao/overview .

[17]  “Laos Yet to Formulate Drought Response Plan,” Vientiane Times , April 29, 2016, accessed May 11, 2016, http://www.vientianetimes.org.la/FreeContent/FreeConten_Laosyet.htm .

[18] Tumpale Sakijege, John Lupala and Shaaban Sheuya, “Flooding, Flood Risks and Coping Strategies in Urban Informal Residential Areas: The Case of Keko Machungwa, Dar es Salaam, Tanzania,” J àmbá: Journal of Disaster Risk Studies 4 (2012): 1-10, accessed April 15, 2016, doi: 10.4102/jamba.v4i1.46.

[19] S. Paul and J. Routray, “Flood Proneness and Coping Strategies: The Experiences of Two Villages in Bangladesh,” Disasters 34 (2010): 489-508, accessed April 15, 2016, doi: 10.1111/j.1467-7717.2009.01139.x.

[20]  “Lao PDR,” The International Rice Research Institute (2015), accessed April 15, 2016, http://irri.org/our-work/locations/lao-pdr .

[21] Amy Kazmin, “Asia Races to Find Drought-Resistant Rice,” Future of the Food Industry , last modified January 13, 2016, http://www.ft.com/cms/s/2/dea46c3e-982a-11e5-9228-87e603d47bdc.html .

[22]  “Lao PDR,” The International Rice Research Institute (2015), accessed April 15, 2016, http://irri.org/our-work/locations/lao-pdr .

[23] A. Phonmart, “Promoting Community Awareness and Strengthening Community Resilience.” Presentation by Department of Disaster Prevention and Mitigation (D.D.P.M.), (Bangkok: Ministry of Interior).

[24] Standing Office of Tien Giang Provincial Committee for Flood and Storm Control (P.C.F.S.C.), “Activities under MRC – ADPC – ECHO Project and Achievement . ”   Presentation at Regional Workshop, Tien Giang, Laos, 2009.

[25]  World Bank, Resilient Recovery: An Imperative for Sustainable Development  (2015), accessed May 8, 2016, https://www.gfdrr.org/sites/gfdrr/files/publication/Resilient-Recovery-An-Imperative-for-Sustainable-Development.pdf .

[26] United Nations Lao PDR, “UN Disaster Risk Reduction Chief: Building Back Better Makes Communities More Resilient,” October 9, 2012, accessed April 15, 2016, http://www.la.one.un.org/media-center/news-and-features/20-un-disaster-risk-reduction-chief-building-back-better-makes-communities-more-resilient .

[27]  “Laos: Floods highlight disaster-preparedness needs,” IRIN , September 7, 2011, accessed May 7, 2016, http://www.irinnews.org/fr/report/93672/laos-floods-highlight-disasterp… .

[28] United Nations Lao PDR, “UN Disaster Risk Reduction Chief: Building Back Better Makes Communities More Resilient.”

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Floods and Your Safety

• Floods, big or small, can have devastating effects on your home and your family. You can take steps to reduce the harm caused by flooding.
• Learn how to prepare for a flood, stay safe during a flood, and protect your health when you return home after a flood.

Prepare for a flood

Floods, big or small, can have devastating effects on your home and your family. Learn how to prepare for a flood, including how to create a plan, supplies you’ll need, and getting your home ready.

Learn more:

• Preparing for a Flood
• Guidelines for Septic and Onsite Wastewater Systems

Stay safe after a flood

Floodwater and standing water can be dangerous and can make you vulnerable to infectious diseases, chemical hazards, and injuries. Know how to protect yourself and your loved ones from the risks brought by floodwater.

• Safety Guidelines: Floodwater After a Disaster or Emergency

Reenter your flooded home

When returning to a home that’s been flooded after natural disasters such as hurricanes, tornadoes, and floods, be aware that your house may be contaminated with mold or sewage, which can cause health risks for your family.

• Safety Guidelines: Reentering Your Flooded Home
• Flood Safety and Preparedness (weather.gov)
• Flood Safety | Flood Preparedness | American Red Cross
• Floods | Ready.gov
• Drinking Water Advisory Communication Toolkit
• Emergency Water Supply Planning Guide
• EPA's Flooded Homes Cleanup Guidance
• Food and Water Safety During Power Outages

Learn how to prepare for a flood and stay safe during and after a flood.

Natural Disasters Essay for Students and Children

500+ words essay on natural disasters.

A Natural disaster is an unforeseen occurrence of an event that causes harm to society. There are many Natural disasters that damage the environment and the people living in it. Some of them are earthquakes , cyclones, floods, Tsunami , landslides, volcanic eruption, and avalanches. Spatial extent measures the degree or severity of the disaster.

Levels of Disaster

The severity or degree of damage can be further divided into three categories:

Small Scale Disasters: Small scale disasters are those that extend from 50 Kms. to 100 Kms. So this kind of disasters does not cause much damage.

Medium-scale disasters: Medium Scale disasters extend from 100 Kms to 500 Kms. These cause more damage than a small scale disaster. Moreover, they can cause greater damage if they occur in colonial states.

Large Scale Disasters: These disasters cover an area of more than 1000 Kms. These cause the most severe damage to the environment. Furthermore, these disasters can even take over a country if the degree is high. For instance, the wiping out of the dinosaurs was because of a large scale natural disaster.

Get the huge list of more than 500 Essay Topics and Ideas

Types of Disasters

Causes: These can cause of releasing of the energy. This release is from the core of the earth. Furthermore, the release of energy causes seismic waves. Rupturing of geological faults causes earthquakes. But other events like volcanic eruptions, landslides mine blasts can also cause it.

Landslides: Landslides is the moving of big boulders of rocks or debris down a slope. As a result, landslides occur on mountains and hilly areas. Moreover, landslides can cause destruction to man-made things in many ways.

Causes: Gravitational pull, volcanic eruptions , earthquakes can cause landslides. Moreover, soil erosion due to deforestation is also a cause of landslides.

Avalanches: Avalanches are like landslides. But instead of rocks thousand tons of snow falls down the slope. Moreover, this causes extreme damage to anything that comes in its way. People who live in snowy mountains always have fear of it.

Causes: Avalanches takes places when there is a large accumulation of snow on the mountains. Moreover, they can also occur from earthquakes and volcanic eruptions. Furthermore, the chances of surviving an avalanche are very less. This is because people die of hypothermia in it.

Tsunami: Tsunami is the production of very high waves in oceans and seas. Moreover, the displacement of the ground causes these high waves. A tsunami can cause floods if it occurs near shores. A Tsunami can consist of multiple waves. Moreover, these waves have a high current. Therefore it can reach coastlines within minutes. The main threat of a tsunami is if a person sees a Tsunami he cannot outrun it.

Causes: Tsunami is unlike normal eaves that occur due to the wind. But Tsunami is waves that occur by ground displacement. Thus earthquakes are the main causes of Tsunamis.

FAQs on Essay on natural disaster

Q1.What are natural disasters?

A1. Natural Disasters are unforeseen events that cause damage to the environment and the people.

Q2.Name some Natural disasters.

A2. Some Natural Disasters are earthquakes, volcanic eruptions, Landslides, floods, Tsunami, avalanches. Natural disasters can cause great damage to human society. But preventive measures can be taken to reduce the damage from these disasters.

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Cold front brings Houston flood, strong storm risk. Here's what you need to know

A flood watch is already in place Thursday to highlight the risk of flooding that's expected later in the day .

Several inches of rain are possible in Houston, with the heaviest rain likely to fall north of Interstate 10. This area of Southeast Texas has been hit hard in recent weeks with multiple rounds of heavy rain and flooding. 

FLOOD WATCH DETAILS: A flood watch is in effect for Houston through Friday morning ahead of several inches of rain to come

In addition to the heavy rain risk, strong storms could pose a damaging wind and hail threat.

Multiple hazards Thursday

Fortunately, the Thursday morning drive was free of problems caused by inclement weather. The potential for heavy rain and strong storms approaches Southeast Texas late Thursday afternoon and into the evening.

KNOW YOUR FLOOD RISK: Use our interactive flood tracker to see what your risk of flooding is.  

High-resolution weather models depict vigorous thunderstorm growth north of Houston during the afternoon hours. This means towns like Conroe and Huntsville will likely see heavy rain arrive in time for the evening commute between 4 and 6 p.m. For Houston, storms are expected to arrive closer to between 7 and 9 p.m. 

Widespread rainfall totals of between 1 and 3 inches are expected across Greater Houston. Higher totals are forecast north of I-10, where the Weather Prediction Center has a rare high risk flash flooding. Rain totals of 2 to 4 inches are expected north of Houston, with locally higher amounts of over 6 inches possible. 

Onshore winds and an approaching cold front work together Thursday to produce the likelihood of heavy rain. Flooding will be the biggest concern Thursday, especially in portions of Trinity, San Jacinto, Polk, and Walker Counties. Portions of these counties have seen 600% of normal rainfall, or 20 to 30 inches, since mid-April.

The Storm Prediction Center has an enhanced risk of severe weather near and north of Houston, which is a level 3 out of 5. This designation means that strong storms may be a bit more numerous in nature, especially closer to Huntsville and College Station. Damaging winds and large hail are primary severe weather threats, but a secondary tornado threat is also on the table through Thursday evening.

Showers and thunderstorms will hug the Upper Texas Gulf Coast through early Friday morning.

Friday showers possible

Friday will be a bit of a transition day for us weather-wise.

The morning starts with storm chances, particularly for areas south of I-10 towards the coast. Intermittent showers and storms may linger through the afternoon in this area as an upper-level disturbance rides along the stalled boundary.

If you're planning to head to Crystal Beach for Jeep weekend, plan on dodging off-and-on storms through Friday afternoon. By no means will Friday be a washout, but there will be a decent chance for rain showers towards coastal communities.

IS HAIL BECOMING MORE COMMON?: Houston has had a lot of severe weather this spring. Is large hail becoming more common?

After a long stretch of rain every couple of days, dry weather is here to stay. 

Hello, summer!

No reason to rub your eyes to make sure you read that last sentence correctly. 

High pressure aloft will establish itself into next week, resulting in a much-needed break from rain. Day after day of sunshine will bring about highs in the lower 90s with heat index values possibly getting above 100 degrees. 

Houston is quite familiar with hot weather, but early season heat is often more dangerous because people haven't gotten used to the warmth. You'll want to practice heat safety next week, especially if you're going to be outside for an extended period. Summer arrives next week for all intents and purposes, friends.

• Anniston/Gadsden

Flash flood warning affecting Mobile County until 2:45 a.m. Tuesday

• Updated: May. 14, 2024, 5:58 a.m. |
• Published: May. 13, 2024, 11:48 p.m.
• Advance Local Weather Alerts

On Monday at 11:41 p.m. the National Weather Service issued a flash flood warning in effect until Tuesday at 2:45 a.m. for Mobile County.

"At 11:41 p.m., Doppler radar indicated thunderstorms producing heavy rain across the warned area. Between 1 and 2 inches of rain have fallen over the past couple hours. Additional rainfall amounts of 1 to 2 inches are possible in the warned area. Flash flooding is ongoing or expected to begin shortly," explains the weather service. "Flash flooding of small creeks and streams, urban areas, highways, streets and underpasses as well as other poor drainage and low-lying areas."

Locations impacted by the warning include Midtown Mobile, Downtown Mobile, Prichard, Tillmans Corner, Chickasaw, I10 And I65, I65 And I165, Tacon, Mertz, Neshota, Navco, Forest Hill, Plateau, West Hill, Whistler, North Mobile, Wheelerville, Eight Mile and Mann.

According to the weather service, "Turn around, don't drown when encountering flooded roads. Most flood deaths occur in vehicles."

Breaking down weather alerts: advisories, watches, and warnings

• Flash flood warning: Take action!

A flash flood warning is issued when a flash flood is either imminent or already occurring. In flood-prone areas, it's crucial to move immediately to higher ground. A flash flood is a sudden and violent inundation that can develop within minutes to hours, and it can even happen in areas not currently experiencing rainfall.

• Flood warning: Take action!

A flood warning is declared when flooding is on the verge of happening or is already underway.

• Flood advisory: Be aware:

A flood advisory is released when flooding is not expected to reach a severity level necessitating a warning. Nonetheless, it can still cause considerable inconvenience and, without exercising caution, potentially lead to situations that threaten life and/or property.

• Flood watch: Be prepared:

A flood watch is issued when conditions are favorable for flooding. It doesn't guarantee that flooding will occur, but it signifies that the possibility exists.

Be flood-ready: Expert guidance from the weather service for your safety

Floods can pose a significant threat, especially if you live in a flood-prone area or find yourself camping in a low-lying region. To ensure your safety, the weather service offers essential flood safety guidelines:

1. Move to higher ground:

• If you reside in a flood-prone region or are camping in low-lying terrain, the first step to safety is relocating to higher ground.

2. Adhere to evacuation orders:

• If local authorities issue an evacuation order, heed it promptly. Prior to leaving, secure your home by locking it.

3. Disconnect utilities and appliances:

• If time permits, disconnect your utilities and appliances. This precaution minimizes electrical hazards during flooding.

4. Avoid basements and submerged areas:

• Avoid basements or rooms submerged in water with electrical outlets or cords. Preventing electrical accidents is crucial.

5. Swift evacuation for your safety:

• If you notice sparks or hear buzzing, crackling, snapping, or popping noises, evacuate immediately. Avoid any water that may be charged with electricity.

6. Refrain from walking in floodwaters:

• Never attempt to walk through floodwaters, even if they appear shallow. Just 6 inches of fast-moving water can forcefully sweep you off your feet.

7. Seek higher ground when trapped:

• Should you become trapped by moving water, reach the highest point possible and dial 911 to contact emergency services.

During heavy rainfall, there is a risk of flooding, especially in low-lying and flood-prone areas. Remember to never drive through water on the road, even if it seems shallow. According to the NWS, as little as 12 inches of rapidly flowing water can carry away most cars. Prioritize your safety by staying informed and prepared.

Navigating rainy roads: Safety tips for wet weather

When heavy rain sets in, the risk of flooding and hazardous driving conditions rises. Whether it's prolonged rainfall or rapid runoff, being prepared is essential. Here are some valuable safety tips from the weather service to ensure you stay safe in heavy rain:

Beware of swollen waterways:

• In heavy rain, refrain from parking or walking near culverts or drainage ditches, where swift-moving water can pose a grave danger.

Maintain safe driving distances:

• Adhere to the two-second rule for maintaining a safe following distance behind the vehicle in front of you. In heavy rain, allow an additional two seconds of distance to compensate for reduced traction and braking effectiveness.

Reduce speed and drive cautiously:

• On wet roads, reducing your speed is crucial. Ease off the gas pedal gradually and avoid abrupt braking to prevent skidding.

Choose your lane wisely:

• Stick to the middle lanes on multi-lane roads to minimize the risk of hydroplaning, as water tends to accumulate in outer lanes.

Prioritize visibility:

• Turn on your headlights and be careful of other vehicles to the rear and in blind spot areas as they are especially difficult to see through rain-spattered windows.

Watch out for slippery roads:

• The initial half-hour of rain is when roads are slickest due to a mixture of rain, grime, and oil. Exercise heightened caution during this period.

Keep a safe distance from large vehicles:

• Large trucks and buses can reduce your visibility with tire spray. Avoid tailgating and pass them swiftly and safely.

Mind your windshield wipers:

• Overloaded wiper blades can hinder visibility. If rain severely limits your sight, pull over and wait for conditions to improve. Seek refuge at rest areas or protected spots.
• When stopping by the roadside is your only option, position your vehicle as far off the road as possible, ideally beyond guardrails. Keep your headlights on and activate emergency flashers to alert other drivers of your position.

By following these safety measures, you can significantly reduce risks and ensure your well-being when heavy rain pours down. Stay informed about weather conditions and heed advice from local authorities to make your journey safe and sound.

Advance Local Weather Alerts is a service provided by United Robots, which uses machine learning to compile the latest data from the National Weather Service.

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Officials brace for a surge of college students on Lake Shasta this weekend

U.S. Forest Service and Shasta County sheriff's officials are expecting a busy weekend on Lake Shasta as college students from Oregon are expected to make an annual trek to California to unwind on the water for Mother's Day weekend.

Most of the students rent houseboats and flock to Slaughterhouse Island near the Sacramento Arm on Lake Shasta. In years past there have been problems on the lake as students have left behind large amounts of trash, and some weekends have turned deadly.

At least four visiting students from Oregon universities have died at the lake since 2001.

Large numbers of students from universities in Oregon, as well as UC Davis, are expected on Mother's Day weekend and Memorial Day weekend, said Joe Stubbendick, a forest service recreation officer for the Shasta Lake Ranger District.

For the second-straight year, lake visitors will find good conditions for boating and camping.

The reservoir is 97% full, according to the U.S. Bureau of Reclamation, which operates Shasta Dam. And the weather this weekend is expected to be sunny, with high temperatures in the low 90s.

Stubbendick said he based the number of student visitors in years past on the number of houseboats that have been seen moored near Slaughterhouse Island.

"I would say that we've had dozens of houseboats lined up side by side along the shore, with most of those houseboats at capacity in terms of what's authorized on those boats," Stubbendick said.

Safety is 'biggest concern'

Officials try to get the message to students and others visiting the lake to pack out what they pack in and not leave trash behind. They also urge them to be safe while boating, especially if they are drinking, Stubbendick said.

"Safety is the biggest concern. We want to be able to give kids, not just students, but to have all recreators have a safe place to recreate, and if they're partaking and in that kind of party scene that they're doing it in a responsible manner. And boats are dangerous. Swimming and alcohol don't exactly mix," Stubbendick said.

Sheriff's Sgt. Chris Van Eyck said he expects the Memorial Day holiday would draw an even larger number of students out to visit the lake.

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The Mother's Day influx will serve as a warm-up for the Boating Safety Unit's first weekend on the lake this season, Van Eyck said. The forest service and marina owners around the lake also work with student groups, urging them to be safe and responsible about drinking and not leaving behind trash, Van Eyck said.

Background on past incidents on the lake

Students from the University of Oregon made national headlines in 2016 when members of the Lambda Chi Alpha fraternity land other students left behind so much trash that a campground on the Slaughterhouse Island was declared a biohazard site.

After the weekend party, they left the island littered with trash, human waste and almost 100 tents.

Weekend partying has also turned deadly on the lake . The most recent death was May 19, 2018, when a 21-year-old University of Oregon student was found dead in his tent near the lakeshore.

Witnesses told boating safety officials he had been drinking before going to his tent the night before, but officials said at the time that was unclear whether alcohol played a role in the death.

Another Oregon State student died in 2001 after slipping and falling off a houseboat. Two students from Oregon schools died in 2005, one who hanged herself and another who drowned, officials said.

Van Eyck said deputies patrolling the lake try to take an educational approach to working with the students, warning them against such infractions as riding on the bow of a boat, wearing life jackets or riding on the side of a boat while it is underway.

He also had a message for others on the lake to be aware of the students on the lake.

"If the general public is going out there. Just be aware that you have an influx of students that don't necessarily have the boating experience that a lot of the citizens around this county have, so just be extra cautious," Van Eyck said.

Reporter Damon Arthur welcomes story tips at 530-338-8834, by email at [email protected] and on X, formerly known as Twitter, at  @damonarthur_RS . Help local journalism thrive by  subscribing today !

Update: Allegheny County under a flash flood warning Wednesday night

• Updated: May. 15, 2024, 9:15 p.m. |
• Published: May. 15, 2024, 8:45 p.m.
• Advance Local Weather Alerts

On Wednesday at 9:04 p.m. the National Weather Service issued an updated flash flood warning in effect until 10:30 p.m. for Allegheny County.

"At 9:04 p.m., Doppler radar showed thunderstorms producing heavy rain across the warned area. Between 1.5 and 2.5 inches of rain have fallen. Additional rainfall amounts of 0.5 to 1 inch are possible in the warned area. Flash flooding is already occurring," states the weather service. "Flash flooding of small creeks and streams, urban areas, highways, streets and underpasses as well as other poor drainage and low-lying areas."

Locations impacted by the warning include Pittsburgh, Mount Lebanon, Bethel Park, Upper St. Clair, Scott Township, Dormont, Castle Shannon, Bridgeville and South Fayette Township.

According to the weather service, "Turn around, don't drown when encountering flooded roads. Most flood deaths occur in vehicles. Be especially cautious at night when it is harder to recognize the dangers of flooding."

Understanding the differences between advisories, watches, and warnings

• Flash flood warning: Take action!

A flash flood warning is issued when a flash flood is imminent or occurring. If you are in a flood-prone area, move immediately to high ground. A flash flood is a sudden violent flood that can take from minutes to hours to develop. It is even possible to experience a flash flood in areas not immediately receiving rain.

• Flood warning: Take action!

A flood warning is issued when flooding is imminent or occurring.

• Flood advisory: Be aware:

A flood advisory is issued when flooding is not expected to be bad enough to issue a warning. However, it may cause significant inconvenience, and if caution is not exercised, it could lead to situations that may threaten life and/or property.

• Flood watch: Be prepared:

A flood watch is issued when conditions are favorable for flooding. It doesn't guarantee that flooding will occur, but it signifies that the possibility exists.

Be flood-ready: Expert guidance from the weather service for your safety

Floods can pose a significant threat, especially if you live in a flood-prone area or find yourself camping in a low-lying region. To ensure your safety, the weather service offers essential flood safety guidelines:

1. Seek higher ground:

• If you reside in a flood-prone region or are camping in low-lying terrain, the first step to safety is relocating to higher ground.

2. Follow evacuation orders:

• If local authorities issue an evacuation order, heed it promptly. Prior to leaving, secure your home by locking it.

3. Disconnect utilities and appliances:

• If time allows, disconnect your utilities and appliances. This reduces the risk of electrical hazards during flooding.

4. Avoid basements and submerged areas:

• Steer clear of basements or rooms where water has submerged electrical outlets or cords. This helps prevent electrical accidents.

5. Swift evacuation for your safety:

• If you notice sparks or hear buzzing, crackling, snapping, or popping noises, evacuate immediately. Avoid any water that may be charged with electricity.

6. Refrain from walking in floodwaters:

• Never attempt to walk through floodwaters. Even just 6 inches of swiftly moving water can forcefully knock you off your feet.

7. Seek high ground if trapped:

• Should you become trapped by moving water, reach the highest point possible and dial 911 to contact emergency services.

During periods of heavy rainfall, especially in low-lying and flood-prone areas, the risk of flooding escalates. Remember this crucial advice: never attempt to drive through water on the road, even if it appears shallow. According to the weather service, as little as 12 inches of rapidly flowing water can carry away most vehicles. Stay safe by being prepared and informed.

Rainy roadways ahead: Essential safety tips for heavy rain

Heavy rainfall may lead to flooding if prolonged or if there is excessive runoff. Excessive runoff can be a result of saturated ground and/or rainfall intensity. Follow these recommendations from the weather service to stay safe in heavy rain:

Beware of rapid water flow:

• In heavy rain, refrain from parking or walking near culverts or drainage ditches, where swift-moving water can pose a grave danger.

Maintain safe driving distances:

• Adhere to the two-second rule for maintaining a safe following distance behind the vehicle in front of you. In heavy rain, allow an additional two seconds of distance to compensate for reduced traction and braking effectiveness.

Slow down and stay cautious:

• On wet roads, reducing your speed is crucial. Ease off the gas pedal gradually and avoid abrupt braking to prevent skidding.

Choose your lane wisely:

• Stick to the middle lanes to minimize the risk of hydroplaning. Outer lanes are more prone to accumulating water.

Prioritize visibility:

• Enhance your visibility in heavy rain by turning on your headlights. Watch out for vehicles in blind spots, as rain-smeared windows can obscure them.

Watch out for slippery roads:

• The initial half-hour of rain is when roads are slickest due to a mixture of rain, grime, and oil. Exercise heightened caution during this period.

Keep a safe distance from large vehicles:

• Don't follow large trucks or buses too closely. The spray created by their large tires reduces your vision. Take care when passing them as well; if you must pass, do so quickly and safely.

Mind your windshield wipers:

• Overloaded wiper blades can hinder visibility. If rain severely limits your sight, pull over and wait for conditions to improve. Seek refuge at rest areas or protected spots.
• If the roadside is your only option, pull off as far as possible, preferably past the end of a guard rail, and wait until the storm passes. Keep your headlights on and turn on emergency flashers to alert other drivers of your position.

By following these safety measures, you can significantly reduce risks and ensure your well-being when heavy rain pours down. Stay informed about weather conditions and heed advice from local authorities to make your journey safe and sound.

Advance Local Weather Alerts is a service provided by United Robots, which uses machine learning to compile the latest data from the National Weather Service.

If you purchase a product or register for an account through a link on our site, we may receive compensation. By using this site, you consent to our User Agreement and agree that your clicks, interactions, and personal information may be collected, recorded, and/or stored by us and social media and other third-party partners in accordance with our Privacy Policy.

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