In regions of the country where mountains are present, storms may dump rain or snow which then rushes down the mountain into the lowlands. When heavy storms hit these regions, flash floods may occur. Floods can also occur in coastal regions when unusually high tides and severe winds blow waves onto the lowlands. Sometimes floods are caused by undersea earthquakes. These giant waves can rapidly move long distances, flooding coastal areas hundreds and thousands of miles away.
Floods can also occur when a dam breaks.
Dams are built to hold water back. The water can then be used for irrigation, power or to prevent flooding below the dam. Occasionally, there is more water than can be safely contained or a dam breaks allowing huge quantities of water to surge down the channel. Since there is usually more water than will fit between the banks, large areas are inundated, resulting in tremendous destruction and often with loss of life. Historical Overview Floods have plagued mankind since before recorded history.