A CONCEPTUAL MODEL OF SEDIMENT ROUTING AND SEDIMENT DELIVERY RATIO, THEORY AND APPLICATION IN TUSCANY

The sediment routing assessment is an important task of the recent research in predicting soil erosion rates and defining different soil protection strategies. A better knowledge of this phenomenon is very useful both to undertake the appropriate sediment management policies and to face the risk connected with river dynamic. The authors propose here a simple conceptual sediment transport model, in conjunction with a GIS environment, based on the concept of linear reservoir cascades coupled with the sediment deposition and degradation. The developed model of sediment routing, is used to explain the spatio-temporal heterogeneity of sediment transport processes, their interactions with rainfall and catchment characteristics. The model introduces the Sediment Delivery Ratio (SDR) jointly to a complete river basin hydrology characterization and the sediment deposition processes analysis. The peculiarity of the developed model is its conceptual easiness and the demand of few parameters available by GIS elaborations. The model has been developed and tested, at event scale, on Virginio creek basin, a small watershed in Tuscany (Italy). The research highlights some of the scientific issues involved in quantifying the sediment discharge in the catchment and presents validation results comparing model predictions with sediment transport measurements collected at an experimental gauging sediment station.