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Traditionally, the relationship between flow rate and sediment concentration in rivers has been estimated empirically. However, the problem of empirical data collection is that it is often difficult to cover the entire range of flow rates. Especially higher flow rates are often undersampled, which might lead to an underestimation of modelled sediment transport as flood events are often associated with important erosion events. In order to overcome this limitation, the introduction of the transport capacity concept can establish a safe upper bound of this sediment transport relationship. Nevertheless, given the number of implied variables in this equation, there is a high uncertainty associated with it. In this study, we aim to reduce the uncertainty on the modelled sediment transport by constraining the relation between sediment concentration and flow rate by means of a combination of sensitivity analysis and field data. This theory is implemented in a model that was used to simulate sediment transport in the Guadalquivir river basin, one of the most important rivers in the Mediterranean (56 978 km2). The sediment concentration-flow rate relation was established by combining the empirical data for the lower flow domain and Yang’s total load formula for the upper flow domain. In combination with data from automated gauging networks, the total annual sediment transport was calculated to be between 6.0 106 and 13.1 107 Mg year-1. A global sensitivity analysis of the main parameters of Yang’s equation was done to identify key data input constraints. This revealed that one of the most important parameters was the mean sediment diameter. A field sampling of flood deposits was done inmediately after high flow events to determine its range.


Session R13, Sediment Transport Modeling



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