MORPHODYNAMICS OF THE MEANDERING RIVER: A STUDY ALONG THE SUBARNAREKHA RIVER OF GOPIBALLAVPUR SECTION, WEST BENGAL, INDIA

Rivers not only represent a vital resource for human activity but they are central to an understanding of geomorphology of most regions. A section of the river Subarnarekha (near Gopiballavpur) is considered for the study on bed and bank morphology associated with patterns of process and channel adjustment. The process-based study of alluvial channel has emphasized an alternative and smaller time and space scale for understanding alluvial channel dynamics. The sand-bed of river tract is complicated by the effects of significantly changing bed forms. However, the gravel bed of the river is lying below the depth of 1 meter from the top of the point bar sand bed which is often not mobile until discharges approach bank-full stage. The bank morphology reveals flood signatures of past events. The depositional activity of over bank flow on the floodplain is very different among the riverine system. The class of extreme events determines channel capacity, affecting channel pattern and more frequent events, although at times widely separated in time, controlled bed load movement and bed form adjustment. Variation of grain size is recorded from the outer bank to inner bank at the meandered section of Subarnarekha. Sand splays are significant feature on the over bank deposits particularly at the section of meandered banks. Bank margin cliffs are found on the older depositional bars at the curvature of the channel. All these modification of channel floor and channel bank are product of bank full discharge in the occurrences of floods. Repeated field survey, sediment grain size analysis, measurement of geomorphic features, satellite image analysis and analysis of discharge data reveal the above features of dynamic alluvial channel.