DEMands of Precision: How DEM Resolution Shapes Various Flood Applications

Digital elevation models (DEM) form the backbone of flood related studies. Proper selection of the DEM product is critical to obtain reliable estimates. Most studies aimed at understanding DEM resolution impacts focus on geometric comparisons. A comprehensive structural and functional assessment framework for DEM comparisons is developed here. The structural differences in DEM are used to understand how DEM products produce differing estimates of flooding susceptibility, rainfall-runoff partitioning, sediment flux estimates and impacts of pluvial flooding. While there is no single DEM resolution that is superior, the results indicate that the ASTER-based 30m DEM is generally the least reliable. The widely available 10m 3DEP DEM is well suited for rainfall-runoff partitioning and flood risk and susceptibility mapping applications. Resampling this DEM to 15m resolution yields similar results and can be used in large domain applications. LiDAR based high-resolution DEMs (1m or less resolution) are best suited for pluvial flood delineations and stormwater management. Even 10m DEM is noted to yield inconsistent results. The 30m ASTER-based DEM yields the most conservative estimate of sediment fluxes due to overprediction of slope and altered watershed shape. The high resolution DEM is therefore recommended for this application as well.