The floods of 1931 resulted in 1 to 4 million people being killed. The Yellow River (Huang He) in China has had the four deadliest flood events in world history. Many ancient communities relied heavily on the annual flooding of floodplain valleys on rivers such as The Tigris-Euphrates, the Nile, and the Ganges. Natural flooding of river plains and deltas each year are essential for farming in many areas of the world as the waters bring nutrient rich silt deposits that create very fertile alluvial soils. Residents are often left without power or clean drinking water which can lead to outbreaks of diseases. While sewage systems and power grids can be destroyed.Īfter floodwaters recede, land can be contaminated with hazardous material, such as building debris, fuel and untreated sewage. Infrastructure such as buildings, cars and houses can be left saturated or completely taken by the waters. With most cities and towns located at the coast or next to rivers, flood events can be major natural disasters, causing loss of life and damage to land and property.įloods can damage bridges, roads and other transport links. Severe cases can be caused by tsunami, hurricanes or tropical cyclones. For example, on natural drought hardened or frozen farmland, or on concrete paving.Ĭoastal and estuary flooding is caused by high sea tidal surges and waves that damage and infiltrate coastal defences. Flash floods are the result of a river blockage either natural or artificial (such as a landslide, glacier, or dam) giving way and releasing a massive amount of built up water.Īreal or urban flooding occurs when low-lying impenetrable ground becomes saturated as rainfall cannot run off as quickly as the accumulation of water. They can occur very quickly, often without warning and with little or no excessive rainfall. If the flow rate exceeds the capacity of the river channel then flooding of the surrounding area can occur.įlash floods are extreme versions of a river flooding event. River flooding is the most common type of flood event. There are many types and ways floods can occur, including, due to overflowing rivers, due to extreme coastal events, by natural or artificial ground saturation from excess rainfall, or by catastrophic failure in infrastructure. A flood is the submerging of normally dry land by an overflow of water.ĭepending on their type, floods can develop very slowly over time after extensive rains or in just a few minutes, very quickly, without any sign of rain.įloods can be a localised event affecting a small area of land or a very large disaster that can have an impact on entire islands or river basins.
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