Flood simply means inundation of extensive land area with water for several days in continuation. Generally, floods are considered to be associated with rivers and people conceive floods as the outcome of accumulation of huge volume of water coming out of the rivers through overtopping of river banks during peak discharge period. In fact, flood is an attribute of physical environment and thus is a component of hydrogical cycle of a drainage basin. It may be pointed out that flood is natural phenomenon and is a response to rainfall but it becomes hazard and disaster when it causes colossal loss to human live and property. It is also important to note that floods are also aggravated by human activities and thus flood hazard is both natural as well as man-induced rather man-accentuated phenomenon. Floods are very often associated with alluvial rivers draining extensive alluvial and flood plains. About 3.5 per cent of the total geographical area of the world is covered by flood plains which house about 16.5 per cent of the total population of the world. The most notorious rivers of the world in terms of devastating floods 2^nd resultant damage to natural environment (riparian decay) and loss of human lives and property are the Ganga and its major tributaries.