Downstream changes in riverbank sediment sources and the effect of catchment size

Abstract

Study region: In this study, we compiled and analyzed the results of previous sediment fingerprinting research that examined the riverbank as one of the sediment sources, representing 118 catchments across the globe, most of which were located in the UK (n = 84), the USA (n = 14), and Brazil (n = 10). Gathered studies included catchments ranging from 0.31 to 15,000 km2 and which were predominately agricultural. Study focus: It is essential to understand how riverbanks contribute to total sediment load at the catchment scale if we wish to develop better strategies for managing soil loss. Therefore, the main objective of this study was to assess different fingerprinting tracers quantitatively and analyze the influence of catchment size on riverbank erosion. New hydrological insights: We found that radionuclide tracers show the most consistent relative sources contributions. The share of riverbanks to total sediment loss was in the range of 1–25%. At the same time, the relative contributions of riverbanks and surface sources for many catchments exceeded 25% and 90%, respectively. This variability emphasizes the number of factors affecting riverbank erosion. However, despite this, there was a clear shift in contributions from surface sources to riverbanks with increasing catchment size. We suggest that, in nested catchments, there is a need for long-term longitudinal monitoring of sediment loads, including downstream changes of riverbank erosion.