Saint-Mathieu-de-Tréviers, France
Saint-Mathieu-de-Tréviers, France

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Lavabre J.,IRSTEA | Arnaud P.,IRSTEA | Royet P.,IRSTEA | Fine J.-A.,HYDRIS Hydrologie | And 3 more authors.
Houille Blanche | Year: 2010

After the remarkable event of September 2002, the Conseil Général du Gard, owner of 5 flood attenuation dams, decided to proceed to the hydrological studies revision of these dams. SHYPRE and SHYREG Methods were implemented by HYDRIS Hydrologie, parallel to a traditional approach used by BRLi. On the Sénéchas 's dam example, the communication attempts to show the flood hydrographs form impact on the maximum water level reach in the dam. In order to determine the 5 000 years return period maximum water level, the authors introduce the design water level concept, complementary to the design flood concept. The design water level is statistically given by the maximum water level frequency distribution construction. These maximum water levels are obtained by the hydraulic simulation in the dam of each floods generated by the SHYPRE method. In addition to freeing the engineer from the design hydrograph choice, studying directly the design water level has various advantages: the water level frequency distribution determination which can be compared with observed water levels, the return period attribution to a given water level, the possibility of testing various dimensioning assumptions for the flood weir... © Société Hydrotechnique de France, 2010.


Aubert Y.,HYDRIS HYDROLOGIE | Arnaud P.,IRSTEA | Ribstein P.,University Pierre and Marie Curie | Fine J.-A.,HYDRIS HYDROLOGIE
Hydrological Sciences Journal | Year: 2014

The SHYREG method is a flood frequency analysis method that can be applied to any location in the French metropolitan territory for flood risk management. It is based on an hourly stochastic rainfall generator coupled with a simplified distributed rainfall-runoff model. This paper presents the validation of flood frequency estimates made using SHYREG for a wide range of 1605 French catchments. For current return periods (i.e. of up to 10 years), the SHYREG-estimated flood frequency values are consistent with estimates from the generalized extreme value (GEV) distribution based on the Nash-Sutcliffe criterion. For extreme return periods, validation of flood frequency estimates is based on: (a) consistent peak and daily discharges estimated from a long observed flow record; (b) reasonable modelled saturation of the production storage for extreme events; and (c) studying the robustness of the SHYREG method by means of statistical criteria. © 2014 IAHS Press.


Organde D.,Hydris Hydrologie | Arnaud P.,IRSTEA | Moreau E.,3 Novimel | Diss S.,IRSTEA | And 3 more authors.
IAHS-AISH Publication | Year: 2012

The aim of the CRISTAL project (Gestion des CRues par l'Integration des Systèmes Transfrontaliers de prévision et de prévention des bassins versants Alpins) is to develop an operational flood forecasting system for catchments located in the French Southern Alps and Italian Piedmont, based on rainfall data from two dual-polarisation X-band radars. The study deals with the calibration and initialization of the rainfall-runoff model on gauged French catchments (45-461 km2 in area) on the Siagne, Paillon and Roya rivers. The GRD conceptual rainfall-runoff model is calibrated in order to reproduce measured flow. The model initialization consists of establishing a calculation rule to define the value of the daily production parameter in relation to known variables (such as previous rainfall or evapotranspiration). Hydrological simulations of recent events measured by X-band radars are presented and compared with raingauge and water-level records. Copyright © 2012 IAHS Press.


This article presents a comparison between real-time discharges calculated by a flash-flood warning system and post-event flood peak estimates. The studied event occurred on 15 and 16 June 2010 at the Argens catchment located in the south of France. Real-time flood warnings were provided by the AIGA (Adaptation d'Information Géographique pour l'Alerte en Crue) warning system, which is based on a simple distributed hydrological model run at a 1-km2 resolution using radar rainfall information. The timing of the warnings (updated every 15 min) was compared to the observed flood impacts. Furthermore, "consolidated" flood peaks estimated by an intensive post-event survey were used to evaluate the AIGA-estimated peak discharges. The results indicated that the AIGA warnings clearly identified the most affected areas. However, the effective lead-time of the event detection was short, especially for fast-response catchments, because the current method does not take into account any rainfall forecast. The flood peak analysis showed a relatively good correspondence between AIGA- and field-estimated peak values, although some differences were due to the rainfall underestimation by the radar and rainfall-runoff model limitations. © 2014 IAHS Press.


Organde D.,Hydris Hydrologie | Arnaud P.,IRSTEA | Fine J.-A.,Hydris Hydrologie | Fouchier C.,IRSTEA | And 2 more authors.
Revue des Sciences de l'Eau | Year: 2013

The SHYREG method was developed for regional flood frequency analysis to estimate peak flow and flood discharges for various durations (1 h to 72 h) and return periods (2 to 100 years), according to a spatialized approach. For each 1-km2 pixel, the method combines an hourly rainfall model with a simple rainfall-runoff model. The discharge flood frequency estimates are deduced directly from the empirical frequency distributions for the maximum values, which are extracted from very long simulated discharge time series. This gives a database of 1-km2 gridded flood quantiles that can be aggregated for any catchment by using an areal averaging method. The method was regionalized for metropolitan France, excluding Corsica, using flow data from 1,359 gauging stations and regional hydroclimatic and hydrogeological characteristics to describe the variability of the rainfall-runoff model parameter. Such regionalization provides flood discharge quantiles for any catchment in metropolitan France for various durations and return periods. Regarding the method performance, accurate estimates of flood quantiles were produced for peak discharge and mean daily discharge for return periods of two to 10 years for gauged basins in dependent validation and cross-validation. A minimum NASH criterion of 80% is obtained for peak flow and mean daily discharge for the catchments not used in the regionalization process.


This paper presents an overview of the different tools used to extend the rating curve to rare floods on the Réal-Collobrier located in Pierrefeu-du-Var, Southern France. From the 10th to the 14th of November 2011, this catchment was affected by a flood that lasted more than 5 days. The highest water level recorded during this event (4.3 m) exceeded by 2 meters the area of validity of the current rating curve. Two approaches are presented. The first methodology relies on a field survey to calibrate a hydraulic model and determine the priors on water flows. The Bayesian method BaRatin led to estimate a rating curve and its uncertainty interval using the river gauging measurements and the modeled water flows derived from the hydraulic model. The second approach relies on the hydrologic modeling of the watershed. The semi-distributed conceptual model GR3H was forced by catchment rainfall, which were estimated from rain gauges measurements, to produce the hourly flood hydrograph. The results show that both approaches are consistent regarding flood volume and hydrograph shape but aren't on maximum hourly mean discharge. To conclude, we provide an estimation of the return period of this event based on the Shyreg-discharge methodology. © 2013 Société Hydrotechnique de France.


Arnaud P.,IRSTEA | Cantet P.,IRSTEA | Aubert Y.,Hydris Hydrologie
Hydrological Sciences Journal | Year: 2016

Extreme events are rarely observed, so their analysis is generally based on observations of more frequent values. The relevance of the flood frequency analysis (FFA) method depends on its capability to estimate the frequency of extreme values with reasonable accuracy using extrapolation. An FFA method based on stochastic simulation of flood event is assessed based on its reliability and stability. For such an assessment, different training/testing decompositions are performed for a set of data from more than 1000 gauging stations. We showed that the method enables relevant ‘predictive’ estimates, e.g. by assigning correct return periods to the record values that are systematically absent in calibration datasets. The model is also highly stable vis-a-vis the sampling. This characteristic is linked to the use of regional statistical rainfall data and a simple rainfall–runoff model that requires the calibration of only one parameter. Editor D. Koutsoyiannis Associate editor Q. Zhang © 2015 IAHS.


SHYREG method is a hydro meteorological risk estimation method, based on the simulation process. It implements an hourly rainfall generator coupled with hydrological modelling, simplified enough to be regionalized. The method has been calibrated from all hydro meteorological data available at the national level (the French Weather Service raingauges network and the hydrometric Bank flow series entitled HYDRO)c. Then, it was regionalized to provide the rainfall and floods quantiles database. In the context of collaborative work with DGPR, this method was applied to a 50 meters resolution mesh throughout to provide a complete flood quantiles database, wherefore avoiding a repetition of method implementation. The method evaluation was carried out using different thesis works and most recently during the ANR project Extraflo, with the aim of comparing predetermination approaches. The accuracy of the method in estimating rainfall and flowquantiles has been proved. The method takes into account extreme flood behaviour and its link to rainfall, which seems preferable to extrapolation based solely from the flow. The results also showed that the method was stable. Its stability is linked to a parameterization based on average values (for the rainfall generator) and on the stability of the rainfall-runoff relationship. In addition, the approach is implicitly multi-durational. So, only one regionalization meets all the needs in terms of features and hydrological hazards. The national database thus established in such a way has the advantage of providing regional information on hydrolo-gical hazards. However, it is subject to use restrictions related to the nature of the method: the SHYREG flows are natural. This database does not take the presence of hydraulic works or the presence of flood expansion areas into account. It is not suitable for basins subjected to high snowmelt or the presence of karsts... In the use of database, precautions are recommended with calls for vigilance when using. © 2014 Société Hydrotechnique de France.

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