Selecting sites for afforestation to minimize sediment loss from a river basin: Computational complexity of Single and Multiple Flow Direction Methods in raster databases

To minimize the sediment flowing to the outlet of a river catchment with minimal effort or cost, the best areas to perform a certain intervention, e.g., afforestation, must be selected. CAMF is a method that performs this selection process iteratively in a raster geo-database. The original version of CAMF uses a Single Flow Direction (SFD) algorithm to simulate the flow paths. Although SFD is often used in studies related to hydrological applications, it may fail to reflect the nature of flow transport, depending on the topography. This paper describes and analyzes the integration of Multiple Flow Direction (MFD) methods in CAMF, in order to provide more accurate flow simulations in areas with specific topographic characteristics. We compare the computational complexity of CAMF-SFD and CAMF-MFD using two methods: FD8 and D∞, and we discuss the scalability w.r.t. the number of cells involved. We evaluate the behavior of these three variants for sediment yield minimization by afforestation in two catchments with different properties.