Bivariate analysis of floods in climate impact assessments

• Published in: The Science of the total environment Vol. 616-617; pp. 1392 - 1403
• Main Authors: Brunner, Manuela Irene, Sikorska, Anna E., Seibert, Jan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2018
• Subjects: Bivariate flood frequency; Hydrological modeling; Seasonality; Synthetic design hydrographs; Bivariate flood frequency; Synthetic design hydrographs; Hydrological modeling; Seasonality
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.10.176

Climate impact studies regarding floods usually focus on peak discharges and a bivariate assessment of peak discharges and hydrograph volumes is not commonly included. A joint consideration of peak discharges and hydrograph volumes, however, is crucial when assessing flood risks for current and future climate conditions. Here, we present a methodology to develop synthetic design hydrographs for future climate conditions that jointly consider peak discharges and hydrograph volumes. First, change factors are derived based on a regional climate model and are applied to observed precipitation and temperature time series. Second, the modified time series are fed into a calibrated hydrological model to simulate runoff time series for future conditions. Third, these time series are used to construct synthetic design hydrographs. The bivariate flood frequency analysis used in the construction of synthetic design hydrographs takes into account the dependence between peak discharges and hydrograph volumes, and represents the shape of the hydrograph. The latter is modeled using a probability density function while the dependence between the design variables peak discharge and hydrograph volume is modeled using a copula. We applied this approach to a set of eight mountainous catchments in Switzerland to construct catchment-specific and season-specific design hydrographs for a control and three scenario climates. Our work demonstrates that projected climate changes have an impact not only on peak discharges but also on hydrograph volumes and on hydrograph shapes both at an annual and at a seasonal scale. These changes are not necessarily proportional which implies that climate impact assessments on future floods should consider more flood characteristics than just flood peaks. [Display omitted] •Design hydrograph construction is useful for climate change impact studies.•Peak discharges and hydrograph volumes are jointly but not proportionally affected by climate change.•The construction of seasonal design hydrographs is more informative in climate impact studies than the construction of annual design hydrographs.