Regional analysis of multivariate compound coastal flooding potential around Europe and environs: sensitivity analysis and spatial patterns

Camus, Paula; Haigh, Ivan D.; Nasr, Ahmed Abu El; Wahl, Thomas; Darby, Stephen E.; Nicholls, Robert J.

doi:10.5194/nhess-21-2021-2021

Cited by 39 publications

(42 citation statements)

References 60 publications

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“…Indeed, other variables could be studied, such as precipitation, river discharges, or even storm duration the same way as Hs [54]. A sensitivity analysis on these variables could be conducted on this area as in [55]. We can also note that we defined an independent wave event as a 3-day window (see Section 3.1), but [56] note that 25% of extreme wave events are consecutive events that hit the same location in less than a day.…”

Section: Discussionmentioning

confidence: 99%

Deriving the 100-Year Total Water Level around the Coast of Corsica by Combining Trivariate Extreme Value Analysis and Coastal Hydrodynamic Models

Louisor

Rohmer

Bulteau

et al. 2021

JMSE

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As low-lying coastal areas can be impacted by flooding caused by dynamic components that are dependent on each other (wind, waves, water levels—tide, atmospheric surge, currents), the analysis of the return period of a single component is not representative of the return period of the total water level at the coast. It is important to assess a joint return period of all the components. Based on a semiparametric multivariate extreme value analysis, we determined the joint probabilities that significant wave heights (Hs), wind intensity at 10 m above the ground (U), and still water level (SWL) exceeded jointly imposed thresholds all along the Corsica Island coasts (Mediterranean Sea). We also considered the covariate peak direction (Dp), the peak period (Tp), and the wind direction (Du). Here, we focus on providing extreme scenarios to populate coastal hydrodynamic models, SWAN and SWASH-2DH, in order to compute the 100-year total water level (100y-TWL) all along the coasts. We show how the proposed multivariate extreme value analysis can help to more accurately define low-lying zones potentially exposed to coastal flooding, especially in Corsica where a unique value of 2 m was taken into account in previous studies. The computed 100y-TWL values are between 1 m along the eastern coasts and a maximum of 1.8 m on the western coast. The calculated values are also below the 2.4 m threshold recommended when considering the sea level rise (SLR). This highlights the added value of performing a full integration of extreme offshore conditions, together with their dependence on hydrodynamic simulations for screening out the coastal areas potentially exposed to flooding.

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Section: Discussionmentioning

confidence: 99%

Deriving the 100-Year Total Water Level around the Coast of Corsica by Combining Trivariate Extreme Value Analysis and Coastal Hydrodynamic Models

Louisor

Rohmer

Bulteau

et al. 2021

JMSE

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“…The first step in determining extreme events is to define which events are considered to be 'extreme'. There are ways to use automatic threshold approaches for detecting extreme events, but they struggle due to the diverse characteristics in the time series of drivers that cause coastal floods (Camus et al, 2021). River-specific thresholds are only feasible for case studies that can take the local properties, like flood protection or elevation of the surrounding area, into account.…”

Section: Methodsmentioning

confidence: 99%

Compound Flood Events: Analysing the joint occurrence of extreme river discharge events and storm surges in Northern and Central Europe

Heinrich

Hagemann

Weisse

et al. 2022

Preprint

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Abstract. The simultaneous occurrence of extreme events gained more and more attention from scientific research in the last couple of years. These compound extreme events have an increased damage potential, compared to the separate occurrence of extreme events, and became a core topic in risk assessment. It is important to improve our understanding of the underlying mechanisms that can cause compound flood events. Our study focuses on the analysis of potential compound flood events with the following contributions. First, we introduce a Monte–Carlo approach to analyse flood event probabilities in northern and central Europe without the use of copulas or ensembles. Second, we investigate if the number of observed compound extreme events is within the expected range of two standard deviations of randomly occurring compound events. This includes variations of several parameters to test the stability of the identified patterns. Finally, we analyse if the observed compound extreme events had a common driver. The results of our investigation show that rivers along the western facing coasts of Europe experienced a higher amount of compound flood events than expected. In these regions, the vast majority of the observed potential compound flood events seem to be related to the Großwetterlage Cyclonic Westerly.

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“…Couasnon et al, 2020;Titley et al, 2021) and values of ρ are generally higher than those of τ (see, e.g. Camus et al, 2021;Wahl et al, 2015). The results of ρ and τ computed for our analysis show a moderate but significant correlation of the separate loss estimates from EFAS RRA and ReAFFIRM with the insurance claim database (Table 5).…”

Section: Estimated Compound Flood Impactsmentioning

confidence: 99%

Compound flood impact forecasting: integrating fluvial and flash flood impact assessments into a unified system

Láng-Ritter

Berenguer

Dottori

et al. 2022

Hydrol. Earth Syst. Sci.

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Abstract. Floods can arise from a variety of physical processes. Although numerous risk assessment approaches stress the importance of taking into account the possible combinations of flood types (i.e. compound floods), this awareness has so far not been reflected in the development of early warning systems: existing methods for forecasting flood hazards or the corresponding socio-economic impacts are generally designed for only one type of flooding. During compound flood events, these flood type-specific approaches are unable to identify overall hazards or impacts. Moreover, from the perspective of end-users (e.g. civil protection authorities), the monitoring of separate flood forecasts – with potentially contradictory outputs – can be confusing and time-consuming, and ultimately impede an effective emergency response. To enhance decision support, this paper proposes the integration of different flood type-specific approaches into one compound flood impact forecast. This possibility has been explored through the development of a unified system combining the simulations of two impact forecasting methods: the Rapid Risk Assessment of the European Flood Awareness System (EFAS RRA; representing fluvial floods) and the radar-based ReAFFIRM method (representing flash floods). The unified system has been tested for a recent catastrophic episode of compound flooding: the DANA event of September 2019 in south-east Spain (Depresión Aislada en Niveles Altos, meaning cut-off low). The combination of the two methods identified well the overall compound flood extents and impacts reported by various information sources. For instance, the simulated economic losses amounted to about EUR 670 million against EUR 425 million of reported insured losses. Although the compound impact estimates were less accurate at municipal level, they corresponded much better to the observed impacts than those generated by the two methods applied separately. This demonstrates the potential of such integrated approaches for improving decision support services.

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Regional analysis of multivariate compound coastal flooding potential around Europe and environs: sensitivity analysis and spatial patterns

Cited by 39 publications

References 60 publications

Deriving the 100-Year Total Water Level around the Coast of Corsica by Combining Trivariate Extreme Value Analysis and Coastal Hydrodynamic Models

Deriving the 100-Year Total Water Level around the Coast of Corsica by Combining Trivariate Extreme Value Analysis and Coastal Hydrodynamic Models

Compound Flood Events: Analysing the joint occurrence of extreme river discharge events and storm surges in Northern and Central Europe

Compound flood impact forecasting: integrating fluvial and flash flood impact assessments into a unified system

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