A framework for the hydrological assessment of at-site bankfull discharge-width for (semi-) incised Ganga river in Middle Ganga plains

Abstract

Floods and corresponding plains are very important to the river to fulfill its complex bio-geomorphological functions. These functions vary in importance from one river to another river. Hence, in this work an attempt has been made to evaluate bankfull discharge and its width. The analysis is carried out at seven Central Water Commission (CWC) hydro-meteorological sites on main stem of Ganga River. The bankfull discharge is assessed using an approach of ‘partial duration series’ rationally in flood frequency analysis for each CWC site. The region covering at-least a part of its flood plain, i.e., bankfull width is derived using rating curve of respective CWC site and validated using pre-post monsoon cross-sections and google-earth imageries at all CWC sites. The present methodology overcomes the problem of incised and semi-incised rivers. The results are indicative of the likely minimal river space (both essential and desirable) for the seven locations, but unexplained anomalies exist in terms of discharges along the length of the river.