About Floods

What causes flooding?

Every year, flooding kills thousands of people and causes tens of billions of dollars in property damage. Floods are usually considered natural disasters, but human activities have also started to contribute significantly to the increase in fllod deaths and damages. Floods account for about 39% of all deaths from natural disasters - more than any other type.

Effects of flooding

Natural flooding by streams, the most common type of flooding, is caused primarily by heavy rain or rapid melting snow; this causes water in the stream to overflow its normal channel and to cover the adjacent area. Geologically, the flat valley floor next to a stream channel is called a floodplain, however the term is often applied to any low area with the potential for flooding, including certain coastal areas. Floodplains, which include highly productive wetlands, provide natural flood and erosion control, help maintain high water quality, and contribute to the recharging of groundwater. Flooding causes the deposition of fertile soil on the banks of streams or rivers and in floodplain thus resulting in the beginnings of agriculture, and the nearby water source is available for irrigation.

How do humans contribute to flooding?

One way in which humans increase the likelihood of flooding and the resulting damage is by removing water-absorbing vegetation, especially on hillsides. Another is by living on floodplains. In many developing countries, the poor have little choice but to try to survive in flood-prone areas. In developed countries, however, people deliberately settle on floodplains and then expect dams, levees, and other devices to protect them from floodwaters - solutions that don't work when heavier-than-normal rains come. Urbanization increases flooding (even with only moderate rainfall) by replacing vegetation and soil with highways, parking lots, and buildings, which leads to rapid runoff of rainwater.

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