The influence of climate change on suspended sediment transport in Danish rivers

The HIRHAM regional climate model suggests an increase in temperature in Denmark of about 3 degrees C and an increase in mean annual precipitation of 6-7%, with a larger increase during winter and a decrease during summer between a control period 1961-1990 and scenario period 2071-2100. This change of climate will affect the suspended sediment transport in rivers, directly through erosion processes and increased river discharges and indirectly through changes in land use and land cover. Climate-change-induced changes in suspended sediment transport are modelled for five scenarios on the basis of modelled changes in land use/land cover for two Danish river catchments: the alluvial River Ansager and the non-alluvial River Odense. Mean annual suspended sediment transport is modelled to increase by 17% in the alluvial river and by 27% in the non-alluvial for steady-state scenarios. Increases by about 9% in the alluvial river and 24% in the non-alluvial river were determined for scenarios incorporating a prolonged growing season for catchment vegetation. Shortening of the growing season is found to have little influence on mean annual sediment transport. Mean monthly changes in suspended sediment transport between -26% and +68% are found for comparable suspended sediment transport scenarios between the control and the scenario periods. The suspended sediment transport increases during winter months as a result of the increase in river discharge caused by the increase in precipitation, and decreases during summer and early autumn months. Copyright (C) 2007 John Wiley & Sons, Ltd.