Geomorphic Threshold and Sand Mining: A Geo-environmental Study in Kangsabati River

Abstract

Over extraction of sand from channel bed are hampered the natural renewal of sediment, geo-environmental setup and channel geometry of riverine system. Hence, geomorphic threshold is applied to define the resilience capacity of river and significant change of process response system in case of sand mining. Objective of this chapter is to determine the threshold limit of sand mining following several geo-environmental settings like geological, morphological, drainage, soil, and channel planform along with riverine land covers in different segments of Kangsabati River using GIS platform. The results demonstrated that all upper segments fall under resilience of threshold limit due to breakdown of slope and presence of enough sediment outflows than extraction. In contrary, maximum middle and entire lower segments are crossed the threshold limit of riverine system, caused by massive mining induced steep slope and meagre sediment inflow. Moreover, some segments of middle course are situated under resilience pre-stage of the threshold limit stage due to sudden fall of bed slope along with enough sedimentation than extraction. It is a point to note that crossed the threshold limit not only depends on mining intensity but also result of significant change of the responsible hydraulic variables. Hence, maximum hydro-ecological consequences are observed in the over threshold limit segments.