Study on the influence of hard points on the morphology of the Ganges river

Abstract

The present study has been conducted to investigate the influence of natural and manmade hard points on the morphological development of the Ganges river ly~ng within Bangladesh. This study is also aimed to identify the location of natural and manmade hard points along the Ganges River. To carry out the study satellite images covering the period from 1973 to 2003, aerial photographs, historical maps, borehole data, water level and discharge data have been used. All of the data have been collected from CEGIS office. From this study it has been found that over the years Ganges is flowing within a morphologically active corridor within which the channel is highly mobile. Along the both sides of this con"idor, several locations such as Godagari, Rougtha, Talbaria, Shilaidaha, Nazirganj Bazar, Joukura etc are identified where the boundary materials are comprised of cohesive materials (natural hard point) of different degree with respect to erodibility. In addition, there are several locations where bank protection structures (manmade structure) were implemented during the last about 100 years both in Bangladesh and Indian portion along this river. The major identified manmade hard points in Bangladesh portion are spur at Pakkanarayanpur in Chapai Nawabganj, revetment to protect Godagari town, revetment and groyne to protect Rajshahi town, revetment to protect Rajshahi Cadet College at Sarda and guide bund to protect Hardinge Bridge at Pakshi. In Indian side, in addition to the Farakka Barrage, several locations were identified along the right bank where bank protection structures have been set up in the recent years. The study findings show that the presence of any hard points (either natural or manmade) at an aggressive bend along the Ganges river strongly influences the morphology of that particular bend. The presence of hard point not only affects on the erosion-accretion rate but also it influences on the erosion pattern and plan fornl development upstream and downstream of the hard point for a certain period.