Erosion of river terraces as a component of large catchment sediment budgets: A pilot study from the Gangetic Plain

Erosion of river terraces and alluvial interfluves in large catchments may be a significant source of sediment, but is not readily included in sediment budgets because quantification is not straightforward. Here a pond on a large river terrace on the Gangetic Plain in northern India provides: an estimate of the proportion of sheet and rill erosion products that reaches a valley floor and, by analogy, the amount that reaches a channel that drains to a major river; and insights into the sensitivity of this delivery to climate change and land use. Comparison is made between the rate of delivery of the products of sheet and rill erosion to a valley floor with approximate sediment yield from gullies indicating that the latter is likely to be a more significant source of sediment. This is a pilot study and its limitations can guide future research. The construction of sediment budgets in many large catchments worldwide could potentially include the approach reported here. The study also contributes to understanding of human–environment interactions, specifically with regard to sheet erosion of agricultural soils.

► River terraces can be a significant source of sediment in rivers.
► A method for estimating sediment delivery from terraces by sheet erosion is presented.
► Sensitivity to climate and land use changes of sheet erosion rates is evaluated.
► Gullies appear to be the main source of sediment on the Ganga terraces.