Seasonal and Interannual Changes in Sediment Transport Identified through Sediment Rating Curves

AbstractSediment dynamics of lowland rivers are of importance in building resilient strategies to manage environmental change. Yet the effects of natural and anthropogenic disturbances on sediment dynamics are poorly understood. Here a low-frequency suspended sediment sampling data set is used to assess the spatial and temporal variations of suspended sediment fluxes in the River Thames (United Kingdom). Sediment rating curves (SRCs) were used to analyze both the spatial and the temporal variation of catchment-suspended sediment transport. SRC exponents for the River Thames were found to be between 0.21 and 1.13. The 95% confidence interval was also determined through a bootstrapping technique. The seasonal and interannual variability of SRC parameters were analyzed to reveal seasonal and secular changes. The results are used to quantify the seasonal flushing effect, in which suspended sediment concentrations are typically substantially higher during the first floods after the summer dry period. The suspended sediment concentrations of the River Thames during the first floods after summer are estimated to be around 1.5–2 times those of other floods, for a given water discharge. A decrease in the flushing effect which began in the 1990s is observed (around 50% of its original magnitude), which may be attributable to changes in catchment and river channel management.