Author(s): Juan L. Garzon; Oscar Ferreira; Andreia Ferreira; Juana Fortes

Linked Author(s): Juan L. Garzon

Keywords: Coastal Flooding; Wave Overtopping; Early Warning System; XBeach

Abstract: Communities can be vulnerable to wave-induced flooding and the risk is expected to increase with rising sea levels and population growth. Under this threat, early warning systems are relevant instruments for effective risk reduction strategies. These systems combine accurate hazard estimations with risk level classification for specific coastal receptors such as pedestrians. Regarding hazard computations, numerical models are gaining in popularity among the possible tools due to their robustness in simulating wave nearshore processes. Regarding risk level classification, the determination of the limits that trigger those levels requires a detailed evaluation. In this study, SWAN+XBeach (non-hydrostatic mode) is used to simulate wave overtopping at two sites of the Portuguese coast, Praia de Faro and Quarteira, during three storms with varying severity. Two overtopping indicators are simulated to represent coastal flooding: mean overtopping discharge and maximum depth velocity. Field observations of impacts caused by these storms are categorized into four risk levels for pedestrians (no risk, low risk, moderate risk, and high risk). Then, the modelled indicators are used to estimate equivalent risk levels based on limits proposed in previous risk assessment sources such as Coastal Engineering Manual 2002, Eurotop (2018), HIDRALERTA, FLOODsite (2009). The comparison of the observed and estimated risk levels reveals that all sources can identify the high risk and the no risk level episodes. However, some discrepancies between sources are found to estimate moderate risk episodes. This study demonstrates that the proposed methodology is appropriate to simulate wave overtopping and properly characterize risk levels for pedestrians.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221411

Year: 2022