Estimation of the rate of erosion of valley fill deposits in a part of the NW Lesser Himalaya

Abstract

Depositional river terraces in technically active regions are used to determine the relative roles of tectonic and climatic changes in the landscape evolution of an area. Apart from providing evidences of tectonic and climatic shifts, these terraces over a long period act as a source of sediment, which is eroded from them. A terrace located in the Lesser Himalaya of known age and a small drainage network developed over it (indicating it to be the only source of erosion), was studied to estimate the rate of erosion. The rate of erosion was calculated by comparing the pre-erosion topography of the terrace modelled in this study by the present day topography of the terrace. Results show that these stored sediments in the form of a depositional terrace are being eroded at a rate of 190 tonnes/year. The results suggest that the rate at which these sediments are eroded is considerable and contributes significantly to the total sediment budget of the river.