Author(s): Manuel Del Jesus; Salvador Navas

Linked Author(s): MANUEL DEL JESUS, Salvador Navas

Keywords: Flooding risk; Stochastic generation; Hybrid downscaling

Abstract: Flood risk assessments are the result of the evaluation of a chain of processes that starts with precipitation, follows with runoff and streamflow, continues with flooding and ends in the mentioned risk. The usual approach to assess flood risk is the application of design storms, in which rainfall climatologies are used to determine the extreme regime of precipitation from which the return levels associated to the return periods of interest are derived. Once the design storm associated with a given return period has been defined, it is transformed through the aforementioned chain, using hydrological and hydraulic models to derive the induced flooding, from which flooding risk is assessed. Thus, the statistical treatment of variables is normally done in the first link of the chain (precipitation) and the result (one event) is transformed and used to assess flooding risk. Previous works (del Jesus et al., 2019, 2018) have shown that design storms may underestimate flooding impacts, but a more in-depth evaluation of the effects of different modeling decisions needs still to be assessed. In this work, we show a comparison between different modeling decisions for assessing flooding risk. Flood-inducing events are characterized both by design storms and multivariate fully stochastic techniques at the precipitation and streamflow links. Hybrid downscaling is used to statistically characterize flooding and flooding risk. All these experiments are summarized, and the results of the risk assessments in space and time compared. Flooding risk assessments will be carried out for Los Corrales de Buelna, Spain. The main conclusion of the work is that design storms may not answer the question of interest of most risk assessments and that, therefore, their use should be limited. Moreover, the later in the risk chain the statistical analysis is done, the more accurate the risk assessment obtained will be, at the expense of an increased computational cost. References del Jesus, M., Navas Fernández, S., Diez-Sierra, J., 2018. Statistical analysis of flooding using hybrid downscaling, in: Proceedings of the 5th IAHR Europe Congress. Presented at the 5th IAHR Europe Congress. New Challenges in Hydraulic Research and Engineering, Trento. https://doi.org/10.3850/978-981-11-2731-1_276-cd del Jesus, M., Navas, S., Díez-Sierra, J., 2019. Stochastic generation and hybrid downscaling for improving the estimation of return periods of flooding. Presented at the 38th IAHR World Congress, pp. 2745–2747. https://doi.org/10/ghdctz

DOI: https://doi.org/10.3850/IAHR-39WC252171192022256

Year: 2022