Floods are the most common of all natural disasters. They occur in all 50 states in the United States and all countries of the world. Flood waters can collect when the spring rains come , during heavy thunderstorms, or winter snow thaws. Floods can happen very quickly or can build after a few days of rain or snow melt. Towns and cities built in low lying areas or near rivers are especially prone to experience flooding.

The most dangerous kind of flood is when a dam breaks. Huge amounts of water rush over the land without warning and carry heavy amounts of debris from trees, houses, bridges, and just about anything that gets in its way. The rushing water can reach a height of 20 feet and when it is packed with the dangerous debris, it crushes everything in its path. The Johnstown flood happened when a dam burst upstream.

Johnstown Flood May 31, 1889

Flooding of the land happens when lakes and rivers are holding all of the water that they possibly can and rain water from storms continues to collect. The banks of the rivers and lakes begin to overflow with water that it can not hold. Sometimes the flood waters break through weakened areas of protective levees that line the banks of some large rivers. .The water spreads onto (floods) the lowest lying areas that surround the body of water.

Floods can also occur when a temporary weather system, such as a hurricane, hits land. Coastal areas can be flooded by the storm surge that comes as the front edge of the storm hits land. Inland areas can be flooded by heavy rains that collect as the hurricane passes over the land.

Text Citations:

FEMA:
http://www.fema.gov/library/flood.htm