SIMULATION OF FLUVIAL SEDIMENT DYNAMICS THROUGH STRATEGIC ASSESSMENT OF STREAM GAGING DATA: A TARGETED WATERSHED SEDIMENT LOADING ANALYSIS

Near-channel sediment loading (NCSL) is localized and episodic, making it difficult to accurately quantify its cumulative contribution to watershed sediment loading, let alone predict the effects from changes in river discharge from climate change or land management. We developed a methodological framework, using commonly available stream gaging data, for estimating watershed-scale NCSL, a feature generally absent in most watershed models. The method utilizes a network of paired gages that bracket the incised river corridors of 15 tributaries to the Minnesota River, in which near-channel sources are often the dominant contributors of sediment loading. For each set of paired gages, we calculate NCSL as the difference between the upstream and downstream sediment loading minus the field contribution between the gages. NCSL generally increases with river discharge when it exceeds the observed threshold benchmark in the tributaries of Minnesota River Basin; accordingly, we developed a predictive model for quantifying NCSL using river discharge as the independent variable. This approach provides a predictive basis for evaluating the impacts on near-channel sediment supply from land cover change and increases in precipitation and runoff with climate change; as well as, the utility of water conservation efforts designed to attenuate peak river discharges and mitigate near-channel erosion.