Erosion rates obtained from check-dam sedimentation (SE Spain). A multi-method comparison

The main aims of this article are to calculate the erosion rates from sediments accumulated in the check dams and to compare the results with those of other methodologies.The study was carried out in a semi-arid area in the south-east of Spain, in the basin of the river Segura, where 425 check dams have been built in order to prevent silting up of a reservoir built in the estuary. From the records of sediments deposited in the different dikes since their construction, various erosion rates have been calculated. Variations in the rates obtained are very high and explanations have been proffered based on physical parameters like the surface areas of the drainage basins to the dikes, the slope of the channel, the lithology or the year in which the dikes were constructed. The results show that, in general terms, the larger the area and the steeper the incline, the lower the erosion rates. Highest rates were found in lithologies of marls and in dikes which have been operational for only a few years.The erosion rates for the whole set, as well as by sub-basins, have been compared with those obtained through other methods (USLE, Fournier and Bathymetric). The bathymetric rates are similar to those obtained from the dikes (3.95 t/ha/year), but the USLE values are 4.5 fold higher and contrary to those of the dikes.