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How to Prevent and Fight Floods

Causes I: Too Much Rain (1/9)

Heavy monsoon rains turned Indonesia’s capital Jakarta into a huge lake in February 2008. In recent years, Jakarta suffered from more severe floods during monsoon season. Blocked and inefficient sewage pipes and waterways keep the water from draining and aggravate flooding.

Rainfall is the most common cause of flooding. Normally, excess rain water drains through rivers into the sea. But unusually high amounts of rain, melting snow and glaciers, and rivers that have been diverted from their natural floodplains all significantly increase the risk for floods. (Photo: Reuters)

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How to Prevent and Fight Floods

Causes II: Deforestation (2/9)

The 1998 Yangtze River flood was one of the most severe floods China had ever seen. More than 3,000 people lost their lives and millions of acres of cropland were destroyed. Environmentalists and scientists blamed heavy logging along the riverbanks.

Forests use up and hold more water than grass- or farmland. Once the trees are gone, the land suffers from soil erosion and sediment is washed downstream from the mountains, clogging the river. (Photo: Reuters)

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How to Prevent and Fight Floods

Causes III: When The Levees Broke (3/9)

Hurricane Katrina hit New Orleans in August 2005. In the aftermath, the levees protecting the city against the Mississippi River and Lake Pontchartrain could not withstand the buildup of water that came with the storm. Around 80 percent of the city, half of which is below sea level, was flooded.

Levees are made to prevent land from flooding and rivers from overflowing, but they are not built to resist strong hurricanes like Katrina. Settlements in areas that are liable to storms and flooding often lead to avoidable damage or death. (Photo: Reuters)

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How to Prevent and Fight Floods

Impacts I: Water Shortages and Disease (4/9)

Around 30 million people in India, Bangladesh, Bhutan, Pakistan, and Nepal were affected by heavy rainfalls in August 2007, which left more than 2,000 people dead. Bangladesh is particularly vulnerable to flood disasters, because half of the country is only slightly above sea level.

Muddy waters are excellent breeding grounds for bacteria and insects - ideal for spreading infectious diseases. Flood casualties are not only caused by drowning in floodwaters, but also through water-borne epidemics, lack of clean drinking water, and lack of access to health care. (Photo: Reuters)

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How to Prevent and Fight Floods

Impacts II: Flooding the Poor (5/9)

In August 2007, Sudan was also hit by devastating floods. Even if the death toll was low compared to the floods that devastated South Asia the same month, damages were widespread. Many fields and villages were covered by floodwater for months, killing 12,000 livestock animals, 16,000 chickens, and huge amounts of crops.

Destruction, injury, and death are not the only damages caused by floods. Floods also have long-term economic effects like shortages of food and crop supplies or a decline in tourism. In less developed countries, impacts are even worse than in industrialized countries due to lack of flood control and emergency response infrastructure. (Photo: Reuters)

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How to Prevent and Fight Floods

Impacts III: Getting Out of the Mud (6/9)

People clear the streets of Jakarta after heavy floods in February 2007. When the flood waters recede, new problems emerge. Mud, dirt, and debris have to be cleared from the streets, and houses have to be rebuilt.

Financing this can be a big burden. Most people’s property in developing countries is not insured against flooding. Their governments often lack the financial resources to clean up streets or rebuild houses. Because floods are a predictable risk in certain regions, it is difficult to obtain insurance that covers damage due to floods. Even in the U.S., most homeowners' insurance policies do not cover flood damage. (Photo: Reuters)

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How to Prevent and Fight Floods

Benefits I: Turning Damage into Profit (7/9)

Although many parts of Bangladesh suffer from severe floods every year, the country also tries to benefit from the positive effects of floods. Floods bring water and nutrients to otherwise dry lands, make depleted soils more fertile, and renew wetlands.

Some countries like China, Vietnam, and Bangladesh are trying to develop innovative flood management strategies, and adopting new farming systems that are suitable for flooded areas. The challenge is to recognize the benefits of floods and profit from fertile floodplains. (Photo: Reuters)

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How to Prevent and Fight Floods

Flood Defense I: Keeping the Water Out (8/9)

Summer 2002: The overflowing Danube River caused severe floods in parts of Austria, Eastern Germany, and Eastern Europe. The floods led to about 25 billion Euros in insured economic losses.

While deploying sandbags is usually the first and most common way to keep floodwaters out, it is not the most environmentally friendly method. Disposing of contaminated sandbags is costly and difficult. Preventive measures like drainage basins, flow regulation structures, or flood reservoirs help to reduce flood peaks considerably. (Photo: Reuters)

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How to Prevent and Fight Floods

Flood Defense II: The Thames Barrier (9/9)

Around five million people in the U.K. live in areas at risk from flooding. Rising sea levels, storm events, and development on floodplains and low lying coastal regions even increase the risk.

The Thames Barrier, the second-largest movable flood barrier in the world, was completed in 1984. At a cost of 700 million euros, its purpose is to prevent London from exceptionally high tides that would cause the River Thames to overflow. Ten separate movable gates positioned across the river regulate the water flowing through. (Photo: Public Domain/Pingstone)

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