Uncertainty assessment of synthetic design hydrographs for gauged and ungauged catchments

Design hydrographs described by peak discharge, hydrograph volume, and hydrograph shapeare essential for engineering tasks involving storage. Such design hydrographs are inherently uncertain asare classical flood estimates focusing on peak discharge only. Various sources of uncertainty contribute tothe total uncertainty of synthetic design hydrographs for gauged and ungauged catchments. These com-prise model uncertainties, sampling uncertainty, and uncertainty due to the choice of a regionalizationmethod. A quantification of the uncertainties associated with flood estimates is essential for reliable deci-sion making and allows for the identification of important uncertainty sources. We therefore propose anuncertainty assessment framework for the quantification of the uncertainty associated with synthetic designhydrographs. The framework is based on bootstrap simulations and consists of three levels of complexity.On the first level, we assess the uncertainty due to individual uncertainty sources. On the second level, wequantify the total uncertainty of design hydrographs for gauged catchments and the total uncertainty ofregionalizing them to ungauged catchments but independently from the construction uncertainty. On thethird level, we assess the coupled uncertainty of synthetic design hydrographs in ungauged catchments,jointly considering construction and regionalization uncertainty. We find that the most important sources ofuncertainty in design hydrograph construction are the record length and the choice of the flood samplingstrategy. The total uncertainty of design hydrographs in ungauged catchments depends on the catchmentproperties and is not negligible in our case.