Large-scale assessment of spatial variability in stream power distribution: An indicator of channel erosion and deposition potential

Channel morphodynamics, governed by erosion and deposition processes, constitute a relevant aspect of integrated water management planning, and development of sustainable fluvial projects. According to the Water Framework Directive, there is a need for hydromorphological recognition and channel geomorphic adjustment at the national level. Such a large scale excludes field measurements as the primary research method. Instead, methods that require less resources and are based on relatively simple process representations are required. The stream power (SP) concept, combining the effect of channel gradient and discharge, has been widely used for quantitative measurements in geomorphic works at different spatial scales, but not at the national level so far. The primary objective of this study was to estimate total and specific stream power, and detect erosion and deposition patterns along the river network in Poland. Given the dominant role of stream slope in SP spatial variations, the specific objective was to assess the vertical accuracy of high-resolution DEM representing water surface elevations along the river course, and to propose a method for extraction of elevation points along river reaches that increase the accuracy of DEM-derived stream slopes. We demonstrated that DEM generally overestimates the elevation by more than 0.5 m, significantly affecting the DEM-derived stream slope estimation. By extracting minimum water surface elevation from DEM within a 15 m radius from the target cell (river segment endpoint), a substantial improvement was achieved. The difference between the actual and DEM-derived water surface elevation dropped to 0.16 m. The results indicated that the distribution of dominating processes in Polish rivers is strongly governed by the character and origin of the terrain relief and lithological diversity. For regions with flat relief, most channels are generally in the state of equilibrium, whereas in upland and mountainous regions, erosion processes are dominant. This study demonstrates the potential use of the SP concept for mapping channel sensitivity to erosion and deposition dominance at a national scale, which can be relevant for integrated river catchment management.