The Response Units Concept and Its Application for the Assessment of Hydrologically Related Erosion Processes in Semiarid Catchments of Southern Africa

Abstract

Proper management of valuable land resources is of paramount importance especially in regions affected by natural hazards. The sustainable development of land resources depends on the understanding of the processes and dynamics active within the landscape. In Southern African countries water shortage and water quality issues related to soil erosion are a major problem affecting the population in rural and urban areas. Consequently, during the last decade increasing attention has been focussed especially on such issues, and an increasing number of integrated hydrological and erosion studies, including the development and application of respective integrated regionalization concepts, is reflecting this development. The present study deals with the regionalization of spatially distributed hydrological related erosion processes in the catchments of the Mkomazi river (KwaZulu-Natal, South Africa) and the Mbuluzi-river (Kingdom of Swaziland). It was carried out within the framework of an interdisciplinary EU-funded project developing an Integrated Water Resources Management System (IWRMS) in semiarid catchments of Southern Africa. Within this project the concept of “Response Units (RUs)” was applied and adapted as Erosion Response Units (ERUs) to regionalize the distribution of hydrologically induced soil erosion in space and time. ERUs are landscape model entities identifying relative homogeneous hydrological related erosion processes, thus providing a spatially distributed model structure for regionalization. The examples from Southern Africa presented in this paper discuss the methods used to delineate such Response Units integrating remote sensing and GIS techniques.