Assessment of river bank erosion in semi-arid climate regions using remote sensing and GIS data: A case study of Rdat River, Marrakech, Morocco

Abstract

Bank erosion is the process of detachment of material grains constituting the banks under the effect of river water during flood events in a fluvial system in semi-arid regions, which are characterized by irregular floods. The phenomenon of river bank erosion has several environmental impacts on the fluvial ecosystem and studies of it are essential. In this context, the purpose of this study is to provide a simple approach to estimate bank heights in order to evaluate the rate of contribution of river bank erosion to the sediment load of the rivers during the last 32 years and its consequences in the fluvial system. The database considered is Landsat images from 1984 to 2016 and the ALOS PALSAR elevation data of Rdat basin, which is located in the southeast of Marrakech in Morocco, as well as field evidence. These data were processed using remote sensing and GIS tools and then combined to improve the results. The obtained results showed that the river bank of Rdat basin is, significantly, unstable and contributes to the supply of sediments to the river, with a river bank retreat rate of 5 m.yr-1 and an annual volumetric erosion rate of 286.82 m3 yr-1 on average. The sediments released in the river, when eroded from banks, may be the origin of contaminated sediments (phosphorus, Mercury …) as well as the main cause of the filling of the river channel.