Flooding

Although human populations have been victims of natural flooding, their presence and subsequent activities near rivers has also contributed to the problem. In naturally occurring conditions, vegetation captures significant amounts of precipitation and returns it to the atmosphere before it has a chance to hit the ground and be absorbed by the earth; however, certain farming practices, like clear-cutting land and animal grazing, hamper this process. Without the natural growth of vegetation to trap the rain, the ground must absorb more moisture than it would otherwise. When the absorption limit is reached, the likelihood of flooding increases. Similarly, construction of concrete and stone buildings contributes to the problem of flooding. While rain is easily absorbed into sand and other porous materials, it is not easily absorbed by man-made building materials, such as pavement and concrete. These substances cause additional run-off which must be absorbed by the surrounding landscape.