Enhanced flood hazard assessment beyond decadal climate cycles based on centennial historical data (Duero basin, Spain)
<p>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 a...
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| Autores principales: | , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/f1ca6ff58c7941b995a8cf21d32eca96 |
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| Sumario: | <p>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 two-dimensional hydraulic model was implemented to relate flood stages (flood marks and
inundated areas) to discharges. The historical flood records show the
largest floods over the last 500 years occurred in 1860 (3450 m<span class="inline-formula"><sup>3</sup></span> s<span class="inline-formula"><sup>−1</sup></span>),
1597 (3200 m<span class="inline-formula"><sup>3</sup></span> s<span class="inline-formula"><sup>−1</sup></span>) and 1739 (2700 m<span class="inline-formula"><sup>3</sup></span> s<span class="inline-formula"><sup>−1</sup></span>). Moreover, at least 24
floods exceeded the perception threshold of 1900 m<span class="inline-formula"><sup>3</sup></span> s<span class="inline-formula"><sup>−1</sup></span> during the period
(1500–1871). Annual maximum flood records were completed with gauged
water-level readings (pre-instrumental dataset, PRE: 1872–1919) and systematic gauge records (systematic
dataset, SYS:
1920–2018). The flood frequency analyses were based on (1) the expected moments
algorithm (EMA) and (2) the maximum likelihood estimator (MLE) method, using
five datasets with different temporal frameworks (historic dataset, HISTO: 1511–2018; PRE–SYS:
1872–2018; full systematic record, 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 % annual exceedance probability, 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
(<span class="inline-formula"><i>></i>1900</span> m<span class="inline-formula"><sup>3</sup></span> s<span class="inline-formula"><sup>−1</sup></span>) declined, although floods on the range of the
historical perception threshold occurred in 2001 (2075 m<span class="inline-formula"><sup>3</sup></span> s<span class="inline-formula"><sup>−1</sup></span>) and 2013
(1654 m<span class="inline-formula"><sup>3</sup></span> s<span class="inline-formula"><sup>−1</sup></span>). 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.</p> |
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