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BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

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.

The present study focuses on the Balason river running through the Himalayan piedmont zone (near Siliguri, India). The objective of the study is an assessment of the environmental effects of river bed material extraction by humans and the dependence of indigenous people on the river and its ecosystem services. The analysis is based on results of field work consisting of geodetic measurements of the river channel and interviews among the local community from the Nimtijot village. Historical hydrological data were also used for the study. The results of the investigation show that the Balason river is heavily affected by excessive exploitation of river bed material during dry season and the replenishment of extracted material in a monsoon season is not always sufficient. It leads to channel deepening. The local community working in the river heavily depends for its livelihood on continuing this activity. A decreasing amount of bed material to be extracted may lead to degradation of the strong relationship between the local community and their natural environment (river).

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