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it originates and land forming. There are adequate examples of new land being
formed in the Sunderban areas of Indian sub-continent. In contrast to deltaic
formations estuaries develop where the rivers carry less sediment to the ocean
which has steep slopes, strong ocean current and strong tidal effects.
Briefly this is the tale of journey of a river from the hills to the oceans through
flood plains. In fact flood plains are essential component of a river
system. During its journey it faces the advent of civilization, development of
urban areas. Flood, which is a natural phenomenon occurs in most of the rivers
carrying volumes of silt and nutrients adjacent to the river i.e. in the flood plains.
Floods are sometimes devastating causing enormous loss to the habitants.
Dams are constructed in many rivers to thwart the problem of flood. Moreover,
river water that reaches the ocean forms part of the hydrologic cycle, but is lost
for the beneficial use of mankind. Dams also help in storing some amount of
flow of water and are used for irrigation, generate hydroelectricity, drinking wa-
ter supply, etc.
DAMS
Water that falls on the surface as precipitation or as snow melt
ultimately finds its way through streams and nalas to the oceans, thus making it
impossible for human use, either for irrigation, industries, power generation and
for drinking purposes. Humanity from time immemorial is trying to hold the
flowing water by artificial means for its own use. Advancement of science has
made it possible to hold the flowing water for various uses. The dam is such an
artificial hydraulic structure to hold the water by obstructing the flow of water
through rivers, resulting in raising water levels on its upstream side. As a result,
a reservoir is formed in the upstream side submerging large areas on its side.
Consequently, the flow in the downstream side is greatly reduced.
Dams are often classified according to its uses or purpose. Storage dams as
the name signifies store water in the upstream side of the river by making
suitable obstruction structure. Gravity dam is an example. Such
storage dams may be constructed by a wide variety of materials like stone,
concrete, earth, rockfill etc. A barrage or a weir is classified under diversion
dam does not submerge any area by pool of water, but the water level in the
upstream side is slightly raised to direct water through canals.
