BED MATERIAL EXTRACTION AND ITS EFFECTS ON THE FORMS AND PROCESSES OF THE LOWER BALASON RIVER IN THE DARJEELING HIMALAYAS, INDIA

High intensity rains bring about landslides and high surface run - off in the upper catchment of the Balason River. Huge quantities of weathered materials as sediment load are being deposited in the river's lower course. The extent and intensity of this bed material extraction have taken such a toll that immediate attention is necessary to reduce the associated effects on the forms and processes of the Balason River's lower course. In this paper, an attempt has been made to closely analyse the prevailing effects of human interference noticed by the authors during this study. The methodology adopted during this study is field based. The changing cross sections and fluvial characteristic of the river were continuously observed. The extraction of bed materials was done directly from the riverbed and from adjacent flood plains and also from terraces. The extractions are responsible for the prevailing bed erosion and channel diversions because extraction pits are what are left behind. In the long term, if not controlled, the effects would be detrimental to the entire fluvial characteristics of the river.