The destruction of the nation's wetlands may also contribute to moderate floods. The wetlands are the swampy land along the edges of some rivers. When it rains, the wet soil and mud of a wetland acts like a sponge and stores the extra water. But much of America's wetlands have been drained for farmland or to build houses. The only place flood water can go is up and over its normal riverbanks and into areas where it can cause major damage.
Floods are primarily natural events.
Human activity influences the frequency and severity of floods, but they are created by Mother Nature. There is no really workable protection against major floods like those that hit Grand Forks in the spring of 1997 and the Mississippi River Basin in 1993. Our best defense against floods is an understanding of the way people treat their environment and better weather prediction.