Evaluation of remotely-sensed DEMs and modification based on plausibility rules and initial sediment budgets of an artificially-created catchment

To quantify landscape change resulting from processes of erosion and deposition and to establish spatially distributed sediment budgets, models of change can be established from a time series of digital elevation models (DEMs). However, resolution effects and measurement errors in DEMs may propagate to these models. This study aimed to evaluate and to modify remotely-sensed DEMs for an improved quantification of initial sediment mass changes in an artificially-created catchment. DEMs were constructed from photogrammetry-based, airborne (ALS) and ground-based laser scanning (TLS) data. Regions of differing morphological characteristics and vegetation cover were delineated. Three-dimensional (3D) models of volume change were established and mass change was derived from these models. DEMs were modified region-by-region for rill, interrill and alluvial areas, based on logical and hydro-geomorphological principles. Additional DEMs were constructed by combining multi-source, modified data. Models were evaluated by comparison with d-GPS reference data and by considering sediment budget plausibility. Comprehensive evaluation showed that DEM usability depends on a relation between the technique used to obtain elevation data, surface morphology and vegetation cover characteristics. Photogrammetry-based DEMs were suited to quantification of change in interrill areas but strongly underestimated surface lowering in erosion rills. TLS DEMs were best suited to rill areas, while ALS DEMs performed best in vegetation-covered alluvial areas. Agreement with reference data and budget plausibility were improved by modifications to photogrammetry- and TLS-based DEMs. Results suggest that artefacts in DEMs can be reduced and hydro-geomorphic surface structures can be better represented by applying region-specific modifications. Photogrammetry-based DEMs can be improved by combining higher and lower resolution data in defined structural units and applying modifications based on principles given by characteristic hydro-geomorphic evolution. Results of the critical comparative evaluation of remotely-sensed elevation data can help to better interpret DEM-based quantifications of earth-surface processes. Copyright (C) 2012 John Wiley & Sons, Ltd.