Sand quarrying activities in an alluvial reach of Damodar River, Eastern India: towards a geomorphic assessment

Abstract

ABSTRACTRiver is a system in which it always tries to make a balance between input and output. Any type of human intervention may affect the whole system and alluvial rivers give response to this interference through changes in its morphology. This concept has serious implications on the present study of Damodar River (Eastern India). Though the hydrology and morphology of Damodar river have been controlled by human activities over the last 50 years, large-scale excavation of river sand from the Damodar riverbed was initiated in the mid-1990s due to increasing urbanization and industrialization. Mainly, the alluvial reach of lower Damodar river is highly affected by uncontrolled sand excavation. To identify the status of sand mining and assess the geomorphic impacts due to indiscriminate and unscientific sand mining, we select Damodar river in between Sillaghat and Sadarghat of West Bengal. It has been estimated that 8, 35,000 ft3/ day (in peak season) of sand is extracted through 71 sand mining areas only from the 40.625 km channel between Sillaghat and Sadarghat. With the help of Geographic Information System (GIS) and field survey, we tried to identify the effects of this huge extraction of sand on this river, which we mapped through Arc GIS software. From the prepared maps, we have identified that Thalweg dynamics, riverbank erosion, instability of river bars; channel bifurcation and pool-riffle sequence change are the major geomorphic impacts of sand mining. Keeping the above concept in the backdrop, it is essential to have a process-based understanding as well as in-depth study of the river for the sustainable management of this threatened river.