A spatially distributed model for the long-term suspended sediment discharge and delivery ratio of drainage basins

Understanding and quantifying the long-term suspended sediment discharge of drainage basins is a key goal of geomorphology, with important implications for the study of water quality, agricultural sustainability, and the evolution of landscapes and sedimentary basins over geologic timescales. Previous studies have highlighted the importance of relief/slope, precipitation, temperature, vegetation, and soil texture in controlling suspended sediment discharge in natural/undisturbed landscapes. However, globally applicable models currently used to predict suspended sediment discharges are limited because they are based on basin-averaged versions of these properties and do not incorporate all of the controlling variables into a single model. In this paper, I propose a spatially distributed, globally applicable model for the long-term suspended sediment discharge of drainage basins that includes all of the principal controls on suspended sediment discharge previously documented in the geomorphic literature. The model explicitly distinguishes the detachment of sediment on hillslopes and in low-order valleys from the transport of sediment in higher-order alluvial channels. The model uses slope, soil texture, mean monthly rainfall, and mean monthly leaf area index as controlling parameters for the detachment component. The transport component is modeled using a Rouse number-dependent transport criterion that explicitly includes the effects of slope and soil texture. The model is capable of reproducing the long-term sediment yield of 128 global rivers with a Pearson correlation coefficient (R value) of 0.79 using just two free parameters. The model also predicts sediment delivery ratios consistent with those measured in natural drainage basins.