Identifying potential sources of sediment contribution based on
hillslope characterization
Abstract
Hillslopes are responsible for the production and transport of sediments
within a landscape (Gilbert 1877). Since the hillslope gradient and
morphology tend to vary across a landscape, it is expected that the
erosion and sediment delivery would also be non-uniform. In this study,
we explore the probability of the flux at a particular point in the
catchment reaching the river mouth using connectivity and the Revised
Universal Soil Loss Equation (RUSLE) in the Pranmati river catchment (a
small 3rd order Himalayan river catchment within the Ganga River
system). Methodology involves characterising the hillslopes of Pranmati
river catchment centered on land use and land cover units. Using RUSLE,
the sediment yielding capacity of various land cover units are estimated
based on which potential source areas are marked. The sediment
connectivity within the basin is also calculated by generating a
sediment connectivity map of the area using method given by Borcelli et
al. (2008). The catchment is categorized into four classes – (A) Highly
connected zones with high sediment yielding capacity (B) highly
connected zones but low yielding capacity (C) poorly connected zones but
high yielding capacity (D) poorly connected zones and low yielding
capacity. The area is then mapped on the basis of the defined classes
and potential areas of erosion and storage are identified. Our results
show that about 62% of the catchment area has low connectivity implying
sediment flux generated in these zones have a low probability of leaving
the catchment. Only 11% of the catchment area has sediment yield
greater than the mean yield per hectare. The sediment generated from
this small area of the catchment contributes 93% of the total sediment
production of the catchment. References Borselli, L., Cassi, P., &
Torri, D. (2008). Prolegomena to sediment and flow connectivity in the
landscape: a GIS and field numerical assessment. Catena,
75(3), 268-277. Gilbert, G. K. (1877). Geology of the Henry
mountains (pp. i-160). Government Printing Office.