Effect of DEM-smoothing and -aggregation on topographically-based flow directions and catchment boundaries

It is generally assumed that, in humid climates, the groundwater table a subdued copy of surface topography. However, general unlikely to be affected by microtopography as seen high-resolution Digital Elevation Models (DEMs). So far, there has been little guidance on best resolution DEM use determine shape water or direction shallow flow headwater catchments. We, therefore, looked at effects DEM-smoothing and -aggregation calculated directions derived catchment boundaries, identified areas landscape features for which are particularly sensitive smoothing aggregation. For > 40 % area Krycklan study catchment, depend strongly degree aggregation DEM. The four main were: local slopes opposite slope, flat areas, ridges, incised streambanks. To changing boundaries smoothed aggregated DEMs, we drainage locations, representing outlets catchments varying sizes. size first-order streams were most processing These often almost completely out during preprocessing steps. shifts would have large effect balance. This thus highlights need carefully consider areas.