Bare-earth DEM generation from ArcticDEM, and its use in flood simulation

Terrain representation is important in many fields including flood mapping. In urban areas, topography data without ground objects are preferred in flood simulation for multiple concerns. However, the topography data collected by remote sensing techniques all contain the artefacts height to some extent. High-resolution photogrammetry DEMs, like ArcticDEM, are emerging with the widely available possibility while approaches to generate bare-earth DEM from them has yet been fully investigated. In this paper, we used the city of Helsinki as a case study. The optimal filter was selected among two morphological filters (PMF, SMRF) and then was used to generate bare-earth ArcticDEM with its various parameter combinations, generating a filtered ArcticDEM ensemble. Then, the elevation error and the flooding performance for a pluvial flooding scenario of this ensemble were evaluated at 2 m and 10 m resolution, respectively, using the LIDAR DTM as the benchmark. The SMRF was found to be advantageous over PMF and be effective at removing artefacts with broad parameter range. In the optimal ArcticDEM-SMRF the RMSE was reduced by up to 70%, achieving 1.02 m, and the simulated water depth error was reduced to a comparable magnitude expected from the LIDAR DTM simulation of 0.3 m. This paper indicates that the SMRF can be directly applied to generate bare-earth ArcticDEM in urban environment although caution should be taken when using in areas with densely packed buildings or vegetation. The results imply that the high-resolution photogrammetry DEMs have the potential to be an alternative of LIDAR in the future.