Assessment of the watershed DEM mesh size influence on a large dam design hydrograph

The present study aims to assess the digital elevation model (DEM) resolution influence on the peak flow estimation for the design hydrograph of a large dam. This was executed by comparing the design hydrograph peak flows, with respect to a 2000years return period, which wereestimated for the Pietrarossa dam, in the South-East of Sicily, for different DEM spatial resolutions. The methodology consisted of the watershed extraction from the catchment basin in which the directly wired area belongs. Furthermore, the intensity duration frequency (IDF) curves were estimated starting from the observational time seriescollected by two rain gauges located near the dam. Finally, through a rainfall-runoff transformation, the design hydrographs were obtained by using both the watershed and the IDF curves. Considering different spatial resolutions, it was found that both the peak flow and the total volume decreases as the DEM spatial resolution decreases.