Floods take place when normally dry land is covered, or inundated, by water. People have suffered from destructive floods for over 4,000 years of recorded history. Since the beginning of time floods have been the most devastating of natural forces known to man. Floods occur when waters rise above a level of containment in a natural stream or manmade trough. Once the overflow spills over its bank some degree of damage usually results. The damage may be confined to the adjacent local area or it may extend miles from the immediate flood site.
Besides the weather factor, the location of a place contributes to the possibility of flooding. Low-lying areas, such as flood plains, river basins, and coastal plains are often vulnerable to widespread flooding. Various kinds of riverbeds, such as arroyos and wadis, coastal regions, and valleys subject to rain or melted snow run-off are especially prone to flash flooding. Floods are most commonly attributed to ongoing rains, local thunderstorms, hurricanes, tidal waves, typhoons, cyclonic disturbances, and melted snow and ice. Tremendous pressure of swollen rivers can cause water bodies to spill over levees and embankments, causing staggering loss of life and extensive damage to property in the afflicted area. When sea walls, flood gates, dikes, or other kinds of man-made retaining structures designed for controlling the volume of water in reservoirs, dams, and canals break or leak, a major flooding calamity can result. Ninety percent of all disasters in the United States are flood-related. A third of all flood losses in America take place outside flood hazard areas.
The first meterologically recorded flood took place in Holland in 1228 with the loss of 100,000 lives. In the Netherlands, there is a long and