Growing Spatial Scales of Synchronous River Flooding in Europe

Abstract

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.

Trends in Compound Flooding in Northwestern Europe During 1901–2014

“…Although HCWL and river peaks may be caused or influenced by the same event, they may not occur on the same day. Hence, a time window is required to consider this effect (Berghuijs et al, 2019;Czajkowski et al, 2017;Merz et al, 2018;Rowe & Villarini, 2013). Flood peaks that occur within a window of ±7 days typically belong to the same large-scale event (Merz et al, 2018).…”

Concurrent 2018 Hot Extremes Across Northern Hemisphere Due to Human‐Induced Climate Change

“…These projected increases can strongly affect future heat wave impacts and risk of concurrent extremes. Similarly, synchronized river floods can cause excessive damages (Berghuijs et al, 2019). For instance, concurrent heat waves in different agricultural regions can affect global food production (Sarhadi et al, 2018) and consequently increase global food prizes and food insecurity (Tigchelaar et al, 2018).…”

“…For instance, concurrent heat waves in different agricultural regions can affect global food production (Sarhadi et al, 2018) and consequently increase global food prizes and food insecurity (Tigchelaar et al, 2018). Similarly, synchronized river floods can cause excessive damages (Berghuijs et al, 2019).…”

A vision for improving global flood forecasting

“…The rationale behind running global hydrological models is that their consistent and worldwide view can provide probabilistic forecasts for basins and regions where the spatial scale of flood events can Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. exceed far beyond natural or political borders [10] and when no alternative forecast systems are available [11]. As these regions are some of the most vulnerable, the forecasts can help inform government bodies, international humanitarian aid agencies, (re)insurance companies, and affected populations of possible flood or drought risks.…”