An Investigation of DEM Resolution Influence on Flood Inundation Simulation

This study investigates the influence of DEM resolutions on flood inundation simulation. Sanyei drainage area of Tainan City is taken as a case study. The catchment of Sanyei area is 43.7 km2 with a main stream of 6.7km and elevations running from 2 m to 30 m. This study uses 1x1 m LiDAR DEM of Sanyei area as a basis. To do pure 2D flood simulation, the channel elevation is adjusted based on the cross-sectional measurements. The channel adjusted 1x1m DEM is later used as basis to aggregate several DEMs including: 5x5m, 10x10m, 20x20m, 40x40m. Five flood inundation models were built based on the 5 DEMs mentioned above with a same model setting. Results show that the inundation area evaluation increases with coarser DEMs. Specifically, the inundation area given by the 40x40m DEM is 1.5 times greater than that given by the 1x1m DEM. This may not only lead to different decision making in evacuation route and responses, but also the evaluation of economic loss and project planning, etc.