Complex picture for likelihood of ENSO-driven flood hazard

Emerton, Rebecca; Cloke, Hannah; Stephens, Elisabeth; Zsótér, Ervin; Woolnough, Steven J.; Pappenberger, Florian

doi:10.1038/ncomms14796

Cited by 115 publications

(114 citation statements)

References 24 publications

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“…Flooding at individual stations is known to exhibit serial correlation (Douglas et al, 2000;Mallakpour et al, 2017), with flood-rich and flood-poor periods; our results show that at a larger scale, years with widespread flooding are also clustered in time. However, although flood risks in Europe are known to be affected by the El Niño-Southern Oscillation and the North Atlantic Oscillation (Emerton et al, 2017;Nobre et al, 2017;Ward et al, 2014), neither has a measurable correlation with the average European flood synchrony scale ( Figure S5). However, although flood risks in Europe are known to be affected by the El Niño-Southern Oscillation and the North Atlantic Oscillation (Emerton et al, 2017;Nobre et al, 2017;Ward et al, 2014), neither has a measurable correlation with the average European flood synchrony scale ( Figure S5).…”

Section: Resultsmentioning

confidence: 99%

Growing Spatial Scales of Synchronous River Flooding in Europe

Berghuijs

Allen

Harrigan

et al. 2019

Geophysical Research Letters

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River flooding is a common hazard, causing billions of dollars in annual losses. Flood impacts are shaped by the spatial scale over which different rivers flood simultaneously, but this dimension of flood risk remains largely unknown. Using annual flood data from several thousand European rivers, we demonstrate that the flood synchrony scale—the distance over which multiple rivers flood near synchronously—far exceeds the size of individual drainage basins and varies regionally by more than an order of magnitude. These data also show that flood synchrony scales have grown by about 50% over the period 1960–2010. Detrended flood synchrony values are serially correlated, implying that years with spatially extensive floods tend to follow one another. These findings reveal that flood risks are correlated well beyond the individual drainage basins for which flood hazards are typically assessed and managed.

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Section: Resultsmentioning

confidence: 99%

Growing Spatial Scales of Synchronous River Flooding in Europe

Berghuijs

Allen

Harrigan

et al. 2019

Geophysical Research Letters

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“…Given the low correlations we have found here between floodiness and either seasonal total rainfall or other rainfall indicators, forecasts of any of these proxies are unlikely to provide strong signals of increased risk. However, there have been several studies using large-scale climate patterns and sea surface temperatures (SSTs) as predictors of flood risk, most focusing on the role of ENSO in changing global flood risk (Emerton et al, 2017;Ward et al, 2014Ward et al, , 2016. Further research on using SSTs and other climate patterns to directly forecast changes to flooding is merited, to explore whether such forecasts would give stronger indications of change in flood hazard than seasonal climate models of rainfall.…”

Section: Discussionmentioning

confidence: 99%

Should seasonal rainfall forecasts be used for flood preparedness?

Pérez

Stephens

Bischiniotis

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. In light of strong encouragement for disaster managers to use climate services for flood preparation, we question whether seasonal rainfall forecasts should indeed be used as indicators of the likelihood of flooding. Here, we investigate the primary indicators of flooding at the seasonal timescale across sub-Saharan Africa. Given the sparsity of hydrological observations, we input bias-corrected reanalysis rainfall into the Global Flood Awareness System to identify seasonal indicators of floodiness. Results demonstrate that in some regions of western, central, and eastern Africa with typically wet climates, even a perfect tercile forecast of seasonal total rainfall would provide little to no indication of the seasonal likelihood of flooding. The number of extreme events within a season shows the highest correlations with floodiness consistently across regions. Otherwise, results vary across climate regimes: floodiness in arid regions in southern and eastern Africa shows the strongest correlations with seasonal average soil moisture and seasonal total rainfall. Floodiness in wetter climates of western and central Africa and Madagascar shows the strongest relationship with measures of the intensity of seasonal rainfall. Measures of rainfall patterns, such as the length of dry spells, are least related to seasonal floodiness across the continent. Ultimately, identifying the drivers of seasonal flooding can be used to improve forecast information for flood preparedness and to avoid misleading decision-makers.

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“…Together, we can see that the monotonic trend initially observed in the frequency of floods at the global and the sub-spatial scales may be due to the variability in the climate and atmospheric teleconnections. Ward et al (2016) and Emerton et al (2017) have previously demonstrated the role of ENSO in modulating global floods. In addition, Hodgkins et al (2017) demonstrated recently that AMO has a significant negative (positive) relationship with 25-and 50-year flood occurrence for large (medium) catchments in North America (Europe).…”

Section: Millionsmentioning

confidence: 99%

Recent trends in the frequency and duration of global floods

2018

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Abstract. Frequency and duration of floods are analyzed using the global flood database of the Dartmouth Flood Observatory (DFO) to explore evidence of trends during 1985-2015 at global and latitudinal scales. Three classes of flood duration (i.e., short: 1-7, moderate: 8-20, and long: 21 days and above) are also considered for this analysis. The nonparametric Mann-Kendall trend analysis is used to evaluate three hypotheses addressing potential monotonic trends in the frequency of flood, moments of duration, and frequency of specific flood duration types. We also evaluated if trends could be related to large-scale atmospheric teleconnections using a generalized linear model framework. Results show that flood frequency and the tails of the flood duration (long duration) have increased at both the global and the latitudinal scales. In the tropics, floods have increased 4-fold since the 2000s. This increase is 2.5-fold in the north midlatitudes. However, much of the trend in frequency and duration of the floods can be placed within the long-term climate variability context since the Atlantic Multidecadal Oscillation, North Atlantic Oscillation, and Pacific Decadal Oscillation were the main atmospheric teleconnections explaining this trend. There is no monotonic trend in the frequency of short-duration floods across all the global and latitudinal scales. There is a significant increasing trend in the annual median of flood durations globally and each latitudinal belt, and this trend is not related to these teleconnections. While the DFO data come with a certain level of epistemic uncertainty due to imprecision in the estimation of floods, overall, the analysis provides insights for understanding the frequency and persistence in hydrologic extremes and how they relate to changes in the climate, organization of global and local dynamical systems, and country-scale socioeconomic factors.

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Complex picture for likelihood of ENSO-driven flood hazard

Cited by 115 publications

References 24 publications

Growing Spatial Scales of Synchronous River Flooding in Europe

Growing Spatial Scales of Synchronous River Flooding in Europe

Should seasonal rainfall forecasts be used for flood preparedness?

Recent trends in the frequency and duration of global floods

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