Mathematical modeling for incision and width changes caused by gravel mining

Abstract

Among other remarkable impacts, the most important effect of gravel mining in rivers is riverbed degradation. Channel-width changes associated to riberbed incision play a major role in this process. Bed incision is coupled with these changes in channel width: bed shear stress reduces as riverbed widens so that incision process slows down and viceversa, bed shear stress enhances as channel becomes narrower. These processes have been oberved in Gállego River, in NE Spain. In this paper a 1-D mathematical model that accounts for river degradation is presented. In order to test the applicability of the model proposed herein, field data has been collected (sediment mining rates, historical thalweg evolution and hydrological data). Extensive degradation up to 5 m has ocurred within the last 11 km of the river. A good agreement between river bed elevations predicted by the model with those observed in the field is shown.