Publication Date:
2021-06-27
Description:
Compound flooding in coastal regions, that is, the simultaneous or successive occurrence of high sea levels and high river flows, is expected to increase in a warmer world. To date, however, there is no robust evidence on projected changes in compound flooding for northwestern Europe. We combine projected storm surges and river floods with probabilistic, localized relative sea‐level rise (SLR) scenarios to assess the future compound flood hazard over northwestern coastal Europe in the high (RCP8.5) emission scenario. We use high‐resolution, dynamically downscaled regional climate models (RCM) to drive a storm surge model and a hydrological model, and analyze the joint occurrence of high coastal water levels and associated river peaks in a multivariate copula‐based approach. The RCM‐forced multimodel mean reasonably represents the observed spatial pattern of the dependence strength between annual maxima surge and peak river discharge, although substantial discrepancies exist between observed and simulated dependence strength. All models overestimate the dependence strength, possibly due to limitations in model parameterizations. This bias affects compound flood hazard estimates and requires further investigation. While our results suggest decreasing compound flood hazard over the majority of sites by 2050s (2040–2069) compared to the reference period (1985–2005), an increase in projected compound flood hazard is limited to around 34% of the sites. Further, we show the substantial role of SLR, a driver of compound floods, which has frequently been neglected. Our findings highlight the need to be aware of the limitations of the current generation of Earth system models in simulating coastal compound floods.
Description:
Key Points:
We combine high‐resolution projected storm surges with localized sea level rise and projected river floods to assess compound flood hazard in the RCP8.5 scenario
We find decreasing compound flood hazard for 66% of the locations across northwestern Europe.
Models reproduce upper tail dependence between storm surge and river floods, yet discrepancies exist in capturing dependence strength.
Description:
Alexander von Humboldt‐Stiftung (Humboldt Foundation)
http://dx.doi.org/10.13039/100005156
Keywords:
551.489
;
compound flood
;
storm surge
;
river floods
;
sea level rise
;
climate change
;
Europe
Type:
article
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