Why river islands are formed after every big city

Abstract

The perennial rivers have high and wide catchment areas that supply water continuously to the rivers. So, all through the year, they get water for their activities. Large cities emerge around such rivers and congregate as huge urban clusters like Delhi, Varanasi, and Patna. It was quite interesting to note that in all the big rivers like the Ganges, after crossing all big cities are invariably present, big river islands. The perceived cause of this is the heavy deposits by the people, or the slowing down of the river as it flattens up. The cause of the river islands is only partly the dirt thrown into the river by the people but largely because of the soap detergents and acids that produce large amounts of salts leading to precipitate and coagulation through a process called Cataphoresis of the colloidal impurities while crossing the cities. Since the river is slender in the cities due to concertized/solid embankment the flow is fairly fast. So, the whole material is pushed beyond the precincts of the cities. But as the river meanders beyond the city's ambit it spreads wider and slows down. So it gives enough opportunity to the colloids to settle down over some time the same enlarges to form River Island.