Spatially Targeting the Expansion of Agricultural Land in a Mountainous Catchment for Maximal Sediment Export Avoidance: Heuristic Optimization Considering Spatial Interaction

Vegetation cover has a large impact on the soil loss dynamics of non-sealed, natural surfaces. Forests have meaningful effects on avoiding the production and transport of sediment. In this study, a combination of methods was applied to locate areas within a river catchment in the southern Andes of Ecuador that would produce a maximal or minimal impact on the sediment yield when deforested. RUSLE was applied to compute the amount of local sediment production within the study region. Then CAMF-MFD was used to simulate sediment flow throughout the catchment and to select cells with maximal/minimal impact on sediment yield at the catchment outlet and/or the urban border of the populated area within the catchment. Six scenarios were devised taking all possible combinations of two factors: reference areas (outlet, urban border, or the combination of both), and type of optimization (maximal- or minimal-impact afforested areas that would be converted to agriculture). The outcomes showed the results of CAMF-MFD are in the same order of magnitude as the sediment values obtained by related studies. Additionally, this work provides a means, based on scientifically sound methods, to discriminate between afforested areas that may be converted, in case it is required, to agriculture with a minimum impact on sediment yield, and afforested areas that must not, under any circumstances, be converted to land use types that are less protective to the soil.