Effects of variability in probable maximum precipitation patterns on flood losses

Andreas Paul Zischg,Jeffrey Neal,Guido Felder,Jim Freer,Gemma Coxon,Niall Quinn,Paul Bates,Rolf Weingartner

doi:10.5194/hess-22-2759-2018

Abstract

Abstract. The assessment of the impacts of extreme floods is important for dealing with residual risk, particularly for critical infrastructure management and for insurance purposes. Thus, modelling of the probable maximum flood (PMF) from probable maximum precipitation (PMP) by coupling hydrological and hydraulic models has gained interest in recent years. Herein, we examine whether variability in precipitation patterns exceeds or is below selected uncertainty factors in flood loss estimation and if the flood losses within a river basin are related to the probable maximum discharge at the basin outlet. We developed a model experiment with an ensemble of probable maximum precipitation scenarios created by Monte Carlo simulations. For each rainfall pattern, we computed the flood losses with a model chain and benchmarked the effects of variability in rainfall distribution with other model uncertainties. The results show that flood losses vary considerably within the river basin and depend on the timing and superimposition of the flood peaks from the basin's sub-catchments. In addition to the flood hazard component, the other components of flood risk, exposure, and vulnerability contribute remarkably to the overall variability. This leads to the conclusion that the estimation of the probable maximum expectable flood losses in a river basin should not be based exclusively on the PMF. Consequently, the basin-specific sensitivities to different precipitation patterns and the spatial organization of the settlements within the river basin need to be considered in the analyses of probable maximum flood losses.

Highlights

Floods are one of the most damaging natural hazards, accounting for a majority of all economic losses from natural events worldwide (UNISDR, 2015)
We set up a coupled component model for estimating flood losses of extreme flood events in a complex mountainous river basin
On the basis of a Monte Carlo approach, we computed an ensemble of extreme flood events for different precipitation patterns of a 3-day probable maximum precipitation scenario

Summary

Introduction

Floods are one of the most damaging natural hazards, accounting for a majority of all economic losses from natural events worldwide (UNISDR, 2015). For portfolio risk analyses of insurance companies, the estimation of the probable maximum loss is important for fulfilling financial regulations and stability criteria. Critical infrastructure, such as power stations, has to be protected against extreme floods. Insurance companies and governmental institutions are increasingly interested in quantifying flood risks, and especially in estimating the impacts of probable maximum floods leading to high cumulative losses (Burke et al, 2016; Morrill and Becker, 2017) or the destruction of critical infrastructure (Hasan and Foliente, 2015; Mechler et al, 2010; Michaelides, 2014)

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