Development of a sediment delivery model for application in large river basins

This paper presents an analysis of available data on suspended sediment con centrations in rivers within the Yorkshire region. It identifies the main c ontrol on the mean suspended sediment concentration across 62 medium-sized catchments (5-380 km(2)) to be that of land cover/use, with the percentage of cropped and suburban/urban land accounting for 71.5% of the variation be tween catchments. Twenty-two of the sites have associated flow gauging, and analysis of this reveals a strong flow dependence for catchments with a hi gh percentage of arable land. In the case of urbanized catchments, there is considerable scatter owing to the influence of point source inputs: notabl y sewage effluent, combined sewer overflows, drainage from colliery waste a nd mine waters. This scatter is due not only to the inherent variability wi thin these point sources, which is not flow related, but also to the variab le degree of dilution by flow in the main stream. As a first-order approxim ation, a simple regression model, in which sediment concentration is a func tion of the daily mean flow and the percentage of cropped and suburban/urba n land cover can be used to generate daily time-series of sediment concentr ation. This model has been applied within the LOIS catchment delivery model and performs well across a wide range of catchment types. Results are pres ented for four catchments representative of the Yorkshire region. Copyright (C) 1999 John Wiley & Sons, Ltd.