01 Jul 2022
01 Jul 2022
Status: a revised version of this preprint is currently under review for the journal NHESS.

A methodological framework for the evaluation of short-range flash-flood hydrometeorological forecasts at the event scale

Maryse Charpentier-Noyer1, Daniela Peredo2,3, Axelle Fleury4, Hugo Marchal4, François Bouttier4, Eric Gaume1, Pierre Nicolle1, Olivier Payrastre1, and Maria-Helena Ramos3 Maryse Charpentier-Noyer et al.
  • 1GERS/LEE, Univ Gustave Eiffel, Nantes, 44344, France
  • 2UMR Metis, Sorbonne Université, Paris, France
  • 3Université Paris-Saclay, INRAE, UR HYCAR Antony, 92160, France
  • 4CNRM, Université de Toulouse, Météo-France, CNRS, Toulouse, France

Abstract. This paper presents a methodological framework designed for the event-based evaluation of short-range hydro-meteorological ensemble forecasts, in the specific context of an intense flash-flood event characterized by high spatio-temporal variability. The proposed evaluation adopts the point of view of end-users in charge of the organization of evacuations and rescue operations at a regional scale. Therefore, the local exceedance of discharge thresholds should be anticipated in time and accurately localized. A step-by-step approach is proposed, including first an evaluation of the rainfall forecasts. This first step helps to define appropriate spatial and temporal scales for the evaluation. The anticipation of hydrological responses (discharge thresholds) is then analyzed, with a focus on the flood rising limb period, and using simulated flows and zero-future rainfall forecasts as references. Based on this second step, several gauged sub-catchments are selected, at which a detailed evaluation of the forecast hydrographs is finally achieved.

This methodology is tested and illustrated on the October 2018 flash-flood, which affected part of the Aude River basin (south-eastern France). Three ensemble rainfall now casting research products recently proposed by Météo-France are evaluated and compared. The results confirm the added value of these ensembles to improve discharge threshold detection and anticipation, but at the price of a significant increase of false alarms.

Finally, even if the evaluation of ensemble hydro-meteorological forecasts based on a low number of documented flood events remains challenging due to the limited statistical representation of the available data, the evaluation framework proposed herein should contribute to draw robust conclusions about the usefulness of newly developed rainfall ensemble forecast approaches, and about their limits and possible improvements.

Maryse Charpentier-Noyer 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 nhess-2022-182', Anonymous Referee #1, 19 Aug 2022
    • AC1: 'Reply on RC1', Maryse Charpentier--Noyer, 09 Oct 2022
  • RC2: 'Comment on nhess-2022-182', Anonymous Referee #2, 21 Aug 2022
    • AC2: 'Reply on RC2', Maryse Charpentier--Noyer, 09 Oct 2022
  • RC3: 'Comment on nhess-2022-182', Anonymous Referee #3, 23 Aug 2022
    • AC3: 'Reply on RC3', Maryse Charpentier--Noyer, 09 Oct 2022

Maryse Charpentier-Noyer et al.

Maryse Charpentier-Noyer et al.


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Short summary
This paper proposes a methodological framework designed for the event-based evaluation in the context of an intense flash-flood event. The evaluation adopts the point of view of end-users, with a focus on anticipation of exceedances of discharge thresholds. With a study of rainfall forecasts, a discharge evaluation and a detailed look at the forecast hydrographs, the evaluation framework should contribute to draw robust conclusions about the usefulness of newly rainfall ensemble forecasts.