Probabilistic Assessment of Flood Hazard due to Levee Breaches Using Fragility Functions

Abstract

Flood hazard maps are useful tools for land planning and flood risk management in order to increase the safety of flood‐prone areas that can be inundated in the event of levee failure. However, flood hazard assessment is affected by various uncertainties, both aleatory and epistemic. The flood hazard analysis should hence take into account the main sources of uncertainty and quantify the confidence of the results for a given design flood event. To this end, this paper presents a probabilistic method for flood hazard mapping, which considers uncertainty due to breach location and failure time. A reliability analysis of the discretized levee system, performed using the concept of fragility function, enables the preselection of a set of levee sections more susceptible to failure. The probabilities of the breach scenarios (characterized by different breach locations and times) are then calculated using the probability multiplication rule, neglecting multiple breaches. The method is applied to a 96‐km levee‐protected reach in the central portion of the Po River (Northern Italy) and to an adjacent 1,900‐km2 flood‐prone area on the right‐hand side of the river, with a focus on the piping breach mechanism. The numerical simulations are performed through a combined 1D‐2D hydrodynamic model using widespread free software. The results show that the method is effective for probabilistic inundation and flood hazard mapping. In addition, it has the advantage of requiring a smaller computational effort in comparison with the methods based on a classic Monte Carlo procedure.

Floodplains in the Anthropocene: A Global Analysis of the Interplay Between Human Population, Built Environment, and Flood Severity

“…Some countries have implemented (at times controversial) retreat programs as a response to floods through the buyout of properties located in more exposed areas in the floodplains (Binder et al., 2020; Siders, 2019; Sipe & Vella, 2014; Thaler & Fuchs, 2019). Alternatively, countries rely on structural protective measures, such as levees, to reduce the frequency of flooding (Collenteur et al., 2015; D'Oria et al., 2019; Mård et al., 2018; Mazzoleni et al., 2014; Takahasi & Uitto, 2004). However, these measures may lead to the unintended effects of enabling intense urbanization of flood‐prone areas and the subsequent reduction of flood risk awareness, often referred to as the safe development paradox (Di Baldassarre et al., 2019; Haer et al., 2020; Hutton et al., 2019; Kates et al., 2006; White, 1945).…”

Probabilistic Flood Hazard Mapping Considering Multiple Levee Breaches

“…The fragility functions for piping obtained by D’Oria et al. (2019) are used in this study since piping has been documented as the main cause of levee breaching in the middle reach of the Po River (Mazzoleni et al., 2015).…”

An introduction to flood modeling for catastrophe risk management

“…For example, a defense could fail for over‐topping simply when the flood depth exceeds the defense height, but it could also fail through breaching for much lower flood depths. For this reason, flood risk models generally employ probabilistic approaches to model defense failure conditioned to flood magnitude (e.g., D'Oria et al, 2019).…”