Preprints
https://doi.org/10.5194/hess-2021-320
https://doi.org/10.5194/hess-2021-320

  26 Jul 2021

26 Jul 2021

Review status: a revised version of this preprint is currently under review for the journal HESS.

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

Gerardo Benito1, Olegario Castillo2, Juan A. Ballesteros-Cánovas3, Maria Machado1, and Mariano Barriendos4 Gerardo Benito et al.
  • 1National Museum of Natural Sciences, MNCN-CSIC, C/ Serrano 115bis, 28006, Madrid, Spain
  • 2Dpt. Ingeniería Industrial e Ingeniería Civil, Escuela Politécnica Superior, Universidad de Cádiz, 11202 Algeciras, Cádiz, Spain
  • 3Climatic Change Impacts and Risks in the Anthropocene (C-CIA), Institute for Environmental Sciences, University of Geneva, Geneva, Switzerland
  • 4Dpt. d'Història i Arqueologia, Universitat de Barcelona. Montalegre 6, 08001 Barcelona, Spain

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.

Gerardo Benito et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-320', Inês Amorim, 24 Aug 2021
    • AC1: 'Reply on RC1', Gerardo Benito, 08 Sep 2021
    • AC2: 'Reply on RC1', Gerardo Benito, 08 Sep 2021
    • AC5: 'Reply on RC1', Gerardo Benito, 10 Sep 2021
      • RC3: 'Reply on AC5', Inês Amorim, 10 Sep 2021
        • AC6: 'Reply on RC3', Gerardo Benito, 10 Sep 2021
  • RC2: 'Comment on hess-2021-320', Libor Elleder, 31 Aug 2021
    • AC3: 'Reply on RC2', Gerardo Benito, 08 Sep 2021
    • AC4: 'Reply on RC2', Gerardo Benito, 10 Sep 2021

Gerardo Benito et al.

Gerardo Benito et al.

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Short summary
Climate change is expected to increase the intensity of floods but changes are difficult to project. We compiled historical and modern flood data of the Rio Duero (Spain) to evaluate flood hazards beyond decadal climate cycles. Historical floods were obtained from documentary sources, identifying 69 floods over 1250–1871. Discharges were calculated from reported flood heights. Flood-frequency using historical datasets showed the most robust results, guiding on climate change adaptation.