Historical Trend Of Riverbank Erosion Along The Braided River Jamuna

Abstract

The Jamuna, the lower part of the Brahmaputra River of India, enters into Bangladesh at Nageshwari upazila of Kurigram district and meets the Ganges at Aricha, is the most dynamic among the rivers of Bangladesh. This river is one of the largest sand-bed braided rivers in the world which is complex and chaotic by nature. The annual erosion along this river is highest among all rivers in Bangladesh [1]. However, the rate of erosion along this river varies over time and space. It is gathered from historical data that the rate of erosion in the Jamuna River was around 5,000 ha per year in the 1980s while in recent years the rate has been around 2,000 ha per year [2].

Compared to its complexity, data, information and knowledge of the riverbank erosion are not enough. In general, understanding on riverbank erosion process of large braided rivers is limited. Old maps and time-series satellite images during low flow facilitate this study in looking into the historical trend of riverbank erosion process. Bank erosion process has been found to be associated with other factors including natural factors such as change in river width. Being a braided river, the Jamuna has multiple channels. An attempt has been made in this study to find out the response of erosion to the presence of the main channel. Water level and discharge are two important hydrological parameters governing the erosion process. It has been attempted to find out the influence of these indicators. Understanding of the historical trend of the riverbank erosion process along the Jamuna would facilitate the national planners in the context of riverbank protection. The knowledge will also help to understand the bank erosion process of large sand-bed braided rivers elsewhere in the world.