Paleofloods stage a comeback

George, Scott St.; Hefner, Amanda M.; Avila, Judith

doi:10.1038/s41561-020-00664-2

Cited by 30 publications

(14 citation statements)

References 12 publications

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“…Palaeoflood analysis informs current and future flood risk (St. George et al, 2020; Wilhelm et al, 2019). Identifying past flooding patterns helps to determine areas at risk under different management scenarios (Alkema & Middelkoop, 2005; Remo et al, 2009), and quantifying past flood magnitudes helps to assess future discharge extremes (Benito & Thorndycraft, 2005; Schendel & Thongwichian, 2017).…”

Section: Introductionmentioning

confidence: 99%

Late Holocene flood magnitudes in the Lower Rhine river valley and upper delta resolved by a two‐dimensional hydraulic modelling approach

Meulen

Bomers

Cohen

et al. 2021

Earth Surf Processes Landf

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Palaeoflood hydraulic modelling is essential for quantifying ‘millennial flood’ events not covered in the instrumental record. Palaeoflood modelling research has largely focused on one‐dimensional analysis for geomorphologically stable fluvial settings because two‐dimensional analysis for dynamic alluvial settings is time consuming and requires a detailed representation of the past landscape. In this study, we make the step to spatially continuous palaeoflood modelling for a large and dynamic lowland area. We applied advanced hydraulic model simulations (1D–2D coupled set‐up in HEC‐RAS with 950 channel sections and 108 × 103 floodplain grid cells) to quantify the extent and magnitude of past floods in the Lower Rhine river valley and upper delta. As input, we used a high‐resolution terrain reconstruction (palaeo‐DEM) of the area in early mediaeval times, complemented with hydraulic roughness values. After conducting a series of model runs with increasing discharge magnitudes at the upstream boundary, we compared the simulated flood water levels with an inventory of exceeded and non‐exceeded elevations extracted from various geological, archaeological and historical sources. This comparison demonstrated a Lower Rhine millennial flood magnitude of approximately 14,000 m3/s for the Late Holocene period before late mediaeval times. This value exceeds the largest measured discharges in the instrumental record, but not the design discharges currently accounted for in flood risk management.

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Section: Introductionmentioning

confidence: 99%

Late Holocene flood magnitudes in the Lower Rhine river valley and upper delta resolved by a two‐dimensional hydraulic modelling approach

Meulen

Bomers

Cohen

et al. 2021

Earth Surf Processes Landf

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“…Although in the past the use of historical flood archives was mainly considered in academic research circles, recent publication by the US federal government guidelines (England Jr. et al, 2019) shows a growing interest to harness past flood information to evaluate flood hazards and risks (St. George et al, 2020). In the European Union, several countries have proposed the use of past flood data on the probability of future floods, as part of low-regret actions to solve the uncertainty of downscaling climate model results on a local scale (García et al, 2014;European Union, 2021).…”

Section: Introductionmentioning

confidence: 99%

Enhanced flood hazard assessment beyond decadal climate cycles based on centennial historical data

Benito

Castillo

Ballesteros‐Cánovas

et al. 2021

Preprint

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Abstract. Current climate modelling frameworks present significant uncertainties when it comes to quantifying flood quantiles in the context of climate change, calling for new information and strategies in hazard assessments. Here, state-of-the-art methods on hydraulic and statistical modelling are applied to historical and contemporaneous flood records to evaluate flood hazards beyond natural climate cycles. A comprehensive flood record of the Duero River in Zamora (Spain) was compiled from documentary sources, early water-level readings and continuous gauge records spanning the last 500 years. Documentary evidence of flood events includes minute books (municipal and ecclesiastic), narrative descriptions, epigraphic marks, newspapers and technical reports. We identified 69 flood events over the period 1250 to 1871, of which, 15 were classified as catastrophic floods, 16 as extraordinary floods, and 38 as ordinary floods. Subsequently, a 2D-hydraulic model was implemented to relate flood stages (flood marks and inundated areas) into discharges. The historical flood records show the largest floods over the last 500 years occurred in 1860 (3450 m3/s), 1597 (3200 m3/s), and 1739 (2700 m3/s). Moreover, at least 24 floods exceeded the perception threshold of 1900 m3/s during the period (1500–1871). Annual maximum flood records were completed with gauged water-level readings (PRE: 1872–1919) and systematic gauge records (SYS: 1920–2018). The flood frequency analyses were based on (1) Expected Moments Algorithm (EMA) and (2) Maximum Likelihood Estimator (MLE) method, using five datasets with different temporal frameworks (HISTO: 1511–2018, PRE-SYS: 1872–2018, ALLSYS: 1920–2018, SYS1: 1920–1969, and SYS2: 1970–2018). The most consistent results were obtained using the HISTO dataset, even for high quantiles (0.001 % AEP). PRE-SYS was robust for the 1 % AEP flood with increasing uncertainty in the 0.2 % AEP or 500-year flood, and ALLSYS results were uncertain in the 1 % and 0.2 % AEP floods. Since the 1970s, the frequency of extraordinary floods (> 1900 m3/s) declined, although floods on the range of the historical perception threshold occurred in 2001 (2075 m3/s) and 2013 (1654 m3/s). Even if the future remains uncertain, this bottom-up approach addresses flood hazards under climate variability providing real and certain flood discharges. Our results can provide a guide on low-regret adaptation decisions and improve public perception of extreme flooding.

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“…Palaeohydrological information refers to physical evidence left in the landscape by floods (Figure 2b), including sedimentary archives in lakes/reservoirs, floodplains, and slackwater deposits in stable river sections that provide information on flow velocities/energy of past flood events (Patton, 2013; St. George, Hefner, & Avila, 2020). This information is used in hydraulic models to estimate the extent of flood inundation.…”

Section: Introductionmentioning

confidence: 99%

Flood mortality in SE Asia: Can palaeo‐historical information help save lives?

Ziegler¹,

Lim

Wasson

et al. 2020

Hydrological Processes

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Asia is one of the world's most flood-prone regions by many metrics: high flood magnitudes, frequency, severity; the number countries affected, the area of inundation; the number of people at risk; and importantly, flood-related fatalities (AIR, 2014; Luo, Maddoks, Iceland, Ward, & Winsemius, 2015; Table 1). With respect to mortality, nearly all the countries with more than 5,000 flood-related deaths since 1985 are from Asia (11 of 13; Table 1; Figure 1). As we write this commentary, flooding associated with tropical storm Nangka has caused more than 40 deaths in Laos, Cambodia, and Vietnam (Floodlist, 2020).

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Paleofloods stage a comeback

Cited by 30 publications

References 12 publications

Late Holocene flood magnitudes in the Lower Rhine river valley and upper delta resolved by a two‐dimensional hydraulic modelling approach

Late Holocene flood magnitudes in the Lower Rhine river valley and upper delta resolved by a two‐dimensional hydraulic modelling approach

Enhanced flood hazard assessment beyond decadal climate cycles based on centennial historical data

Flood mortality in SE Asia: Can palaeo‐historical information help save lives?

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