What Causes an Area Flood?

Flooding can be one of the most dangerous and expensive natural disasters. From property destruction to drowning and the displacement of large numbers of people, floods can be a devastating occurrence. Some places are obviously more prone to flooding than others. Areas near rivers, lakes or streams and sometimes the ocean are more susceptible to flooding than those in upper elevations, away from major bodies of water.A handful of factors are typically the cause of disastrous flooding that spreads over a large area.

Prolonged Precipitation

• One of the most common reasons for flooding is rain. This type of flooding happens every year in many places, with some places enduring repeated floods. When precipitation falls for an extended period of time, the water that typically drains into nearby rivers or streams under normal circumstances does not have time to clear out in time. The continuing rainfall piles up and has nowhere to go but to flow into the surrounding areas, causing a flood.

Dams and Levees

• Areas near bodies of water that are protected by a dam or levee are susceptible to flooding should the dam or levee give way. A sudden rush of water from a broken levee, such as the rush of water into New Orleans following Hurricane Katrina, can often destroy structures in the path of the flow, catch residents by surprise and result in a large number of drownings.

Tropical Storms

• Heavy rains often accompany tropical storms, which can lead to flooding. When the moist air from the tropics forms a hurricane or tropical storm, large amounts of rain are likely to be involved as the system makes landfall. If the area is ill-equipped to handle the torrential rains, rivers, streams, lakes and other bodies of water are likely to spill over and flood low-lying areas. Coastal regions are typically at low elevations, making this possibility even more likely.

  In addition to the rainfall from a tropical storm or hurricane, there is a natural storm surge that pushes seawater inland and can cause coastal flooding driven by the wind and the sea.

Tsunami

• One of the most frightening causes of flooding is a tsunami. Often created by earthquakes and shifting in the earth's plates, these massive waves of water can travel at high speeds across entire oceans and crash into land with great force, instantly flooding coastal areas and often destroying everything in its path. Luckily, advanced warning systems can warn residents to seek higher ground hours in advance in some cases. However, locally generated tsunamis can strike within minutes, giving no time for warnings.