Inundation of Land

the covering of a land area by water brought about by natural causes (overflowing of rivers, heavy precipitation, or tides) or artificial causes (construction of reservoirs or ponds). Inundation may be long-term, in which case it is usually impossible to use the land (for example, land occupied by the basin of a reservoir), short-term, when use of the land is easy and feasible (for example, land flooded by high waters in the spring), intermittent (caused by tides or by overflowing of rivers in the spring), which can be forecast fairly accurately, or sudden (an elemental disaster caused, for example, by a flood), for which the likelihood of an early warning is very small. In cases of inundation, the soils that remain under water for several years deteriorate as a result of destruction of the soil absorption complex, decomposition of the sod, and gleization; on the other hand, during short-term flooding of river bottomlands by spring high waters, fertile river soils are formed because of the deposition of sediment that is rich in organic material. In certain areas, loss of soil cover and swamping (when water runoff is slow) are also possible. Inundation, particularly sudden inundation, can result in great damage to the national economy (destruction of buildings and other structures, as well as crop damage). Many farm crops (for example, winter grain crops, clover, timothy, and meadow fescue) die even during short-term inundation in the summer.

In arid regions, inundation is used as a method of irrigating rice (surface watering), for water supply (basin irrigation), and for leaching of salt lands. The inundation of land by reservoir waters creates shallow waters (1.5–2.0 m deep), which may be used for breeding fish, waterfowl, and shore animals; the overgrown shallow waters may also become breeding grounds for the development of the malaria mosquito.

The economic use of inundated lands often requires changes in the inundation conditions (periods, duration, and depths). For this reason, the shores of reservoirs, rivers, and seas are dammed up, that is, enclosed by embankments; river beds are regulated in order to reduce the water flow rate or increase their delivery capacity (river channels are deepened, widened, and straightened; rapids and ponds are eliminated); and highland channels and embankments are built to protect the land from flooding by meltwater, rainwater, and runoff water from the surrounding slopes.