Flooding

Because of the potential of a flood to destroy life and property, men and women have, for centuries, developed ways to prepare for and fight this natural disaster. One common way to manage floodwaters is to construct dams to stop excess water from inundating dry areas. Another way is to divert floodwaters away from populated areas to planned areas of flood storage. To this end, flood control reservoirs are kept partially empty so that they can catch floodwaters when the need arises. These reservoirs then release the water at a slower rate than would occur under flood conditions; hence, reservoirs give the soil time to absorb the excess water. About one-third of reservoirs in the United States are used for this purpose.

Two other ways to safeguard life and property are known as "hazard zoning" flood plains and "minimizing encroachment." When hazard zoning a flood plain, planners look at such things as historical records of 40-year floods, geological maps, and aerial photographs to predict likely areas where flooding could occur. Rather than relocating populations, hazard zoning is used for planning the location of new settlements. Minimizing encroachment means carefully planning where buildings are located so that they do not restrict the flow of water or cause water to pond excessively; however, as long as people choose to live in low-lying, flood-prone areas, scientists and engineers can only do so much to protect them from the risks of floods caused by both natural conditions and human activities.