Impact of resolution of DEM on the calculation of design floods in a small mountainous basin

Abstract

A Digital Elevation Model (DEM) is a powerful tool for representing the surface of a particular area of interest. The containing data in the DEM is used for determining the characteristics of the surface. The main factor regarding the quality of such data is the resolution of the DEM. In this paper, the authors focus on the impact of the resolution of the two DEMs that were used to calculate a design flood in the Boca River basin. The Boca River basin is a small mountainous catchment located in the Low Tatras National Park in Slovakia. The authors have used digital elevation models of the Boca River basin with a 20 x 20 m and 1 x 1 m resolution of the raster and the S- JTSK coordinate system. The DEMs were downloaded from the Basic Database for GIS (ZBGIS®) which is a part of the spatial database of the cadastral information system in Slovakia. The design values of short-term rainfalls from actual observations from the Kráľová Lehota - Čierny Váh climatological station and the Corine Land Cover land use map for 2018 were used as an input for the calculation of the design floods. The design floods (QN) were estimated for the return period (N) of 10, 20, 50 and 100 years, using the Soil Conservation Service - Curve Number method, and ArcGIS software and raster tools. The peak design floods were estimated by calculating the time concentration, the maximum potential river basin retention, the design rainfall intensity, the depth of the runoff, and the volume of the flood wave. The aim of the paper was to compare the results of these calculations when the two different quality resolution DEMs are used. The results show that the design floods calculated using the more precise DEM with a 1 x 1 m raster were lower by 3.9% than the design floods calculated using the DEM with the 20 x 20 m raster.