Hanne De Brue

Impact of the spatial and thematic resolution of Holocene anthropogenic land-cover scenarios on modeled soil erosion and sediment delivery rates

Recent reconstructions of global Holocene vegetation may provide a powerful means to quantify long-term cumulative sediment fluxes induced by anthropogenic land-cover changes. However, the former’s low spatial resolutions question their potential for use in geomorphic models, since sediment redistribution processes operate at much smaller scales. Furthermore, current land-cover reconstructions often do not differentiate the typology of human impact, although the susceptibility of different anthropogenic land uses towards erosion varies greatly. Hence, the present study investigates the sensitivity of a spatially distributed erosion and sediment redistribution model to the spatial and thematic resolution of input land-cover information. The geomorphic model was applied to the Scheldt Basin (~19,000 km2) with low-resolution and high-resolution land-cover input, and subsequently compared to a field-based reference sediment budget of the Dijle subcatchment. Results indicate that low-resolution land-cover information, expressed as proportions of different land-cover types within each grid cell, leads to largely overestimated sediment fluxes. In contrast, spatial allocation of individual land-cover types to a 100-m grid yields more accurate results. These variations in model outcomes are related to differences in landscape connectivity between high- and low-resolution land cover. Moreover, geomorphic model results are non-linearly related to the area under cropland. This indicates that there is not only a need for land-cover reconstructions at high spatial resolution but also that differentiation of anthropogenic land-cover types is essential for accurate geomorphic modeling.