The Effects of Spatial Resolution Variability of Digital Elevation Models on Flood Hazard Analysis

Raster-based Digital Elevation Models (DEMs) represent the surface topography as the primary input in flood hazard and risk studies. The study aims to reveal the variability of the hazard at the base of the Ulus settlement by performing flood hazard analyses with different source and resolution DEMs, which are used on a global and local scale and form a primary input for many studies. For this purpose, DEMs data, such as MERIT 90m, FABDEM 30m, TopoDEM 10m, DEM5m, LiDAR 1m, and UAV 0.1m, for the Ulus River basin and settlement and the 500-year flood produced for the river tributaries using the SWAT rainfall-runoff model were used. To examine spatial resolution variability, flood hazard analyses were performed based on the two-dimensional LISFLOOD-FP hydrodynamic model, using a fixed Manning n value (n=0.035). As a result, although there is an increase in cost, time, and model instabilities from low resolution to high resolution, it is essential to choose the most appropriate DEM according to the required detail and scale of the hazard analysis to be able to obtain more accurate results. While the model time and average computational errors from low resolution to high resolution increased, the water extent and the spatial distribution of the hazard classes produced for people and buildings decreased. The FABDEM data is more advantageous in regional studies than others, whereas the LiDAR data can be used in basin-scaled studies. In addition, the DEM5 data also can be used in basin-scaled studies after clearing the heights of the buildings and vegetation groups.