Geomorphic response to riverine land cover dynamics in a quarried alluvial river Kangsabati, South Bengal, India

Abstract

This paper deals with impact of geomorphic responses such as thalweg shifting, sandbar instability, pool-riffle alteration, river bank erosion, channel incision river bed lowering and river bank erosion on riverine land cover dynamics arises by instream and floodplain sand mining in an alluvial reach as Kangsabati River from Mukutmonipur dam to Rajnagar confluence (193 km) during 2002–2016. Four segments i.e. Lalgarh, Mohanpur, Kapastikri and Rajnagar share as 554,656 m ton/year sand from 141 mining sites whereas others segment as Khatra, Raipur, Dherua and Panskura share only 33,497 m ton/year sand from 50 mining sites in the entire channel. Several maps were prepared to identify consequences of morphological responses with the help of field study and GIS technique. Friend and Sinha’s method (Geol Soc Lond 75(1):105–111, 1993) was used to detect planform change with geomorphic responses throughout the course. Pearson correlation matrix is used to establish the relation between geomorphic responses and land cover dynamics incorporates with mining intensity. The result shows that higher value of geomorphic responses decrease sandchar, riparian area but increases channel, mining, pits and clay cover in mining prone segments as Lalgarh, Mohanpur, Kapastikri, and Rajnagar. The lower value of geomorphic responses increase sandchar, riparian area but decreases channel, mining, pit sites and clay cover in sandchar segments as Khatra, Raipur, Dherua and Panskura, respectively. Therefore, sand mining greatly impact on riverine land covers dynamic following instable geomorphic responses. Moreover, this study reveals that sustainable sand mining incorporates with stable geomorphic responses maintain fluvial dynamics controlling of erosion and deposition process.