Modelling gully erosion rates and its impact on catchment sediment yield at the continental scale

In many regions of the world, gully erosion is a process that is responsible for important soil losses and a majority of the sediments transported by river systems. Understanding and quantifying gully erosion (GE) rates and their contribution to catchment sediment yields (SY) is therefore of fundamental scientific importance, but also necessary for the development of suitable land use and catchment management strategies. Nonetheless, our ability to simulate and predict GE remains currently very limited, especially at the continental scale. This research aims to bridge this gap by developing a first spatially explicit and process-oriented model that simulates average GE rates at the continental scale, building on recently obtained insights, model concepts and databases. In a first phase, we will develop a model that can simulate the density of gully heads across Africa. For this, we will develop a framework similar to the simulation of landslide susceptibilities. In a second phase, we will couple this gully density model to a model simulating the expansion rate of individual gully heads. The integration of these two models will result in the very first assessment of gully erosion rates at a continental scale (at decadal timescales). In a last phase, we will confront the simulated gully erosion rates of Africa with a database on measured SYs for >600 catchments. From this we will obtain a first quantification of the overall importance of GE for SYs.