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Poster De Conférence Année : 2012

THE “RHYTMME” PROJECT IN MOUNTAINOUS AREAS USING X-BAND WEATHER RADARS

Résumé

In most cases, natural hazards encountered in mountainous areas are largely dependent on precipitations: flash floods, debris flows, landslides, rock falls, snow avalanches. However, the knowledge of rainfall quantities still remains a tricky issue: the available rain-gauges are in a limited number and most often located in the valleys, and the radar rainfall estimates have to deal with a lot of problems due to the relief and the difficulty to distinguish the different types of hydrometeors (snow, hail, rain). In this context, the “RHYTMME” project (Westrelin and al., 2010) deals with two main issues: -Providing an accurate radar rainfall information in mountainous areas. -Developing a real-time hazards warning system based on this information. In this context, a X-band doppler dual polarized radar network is currently implemented in the French South Alps. It completes a pre-existing radar already installed on the Mont Vial summit since 2008 (Hydrix® technology developed by the Novimet company, and tested in a previous project). The present communication focuses on the flash flood warning system only. This system is based on the AIGA method developed for the ungauged catchments by IRSTEA and METEO-FRANCE for a decade. (Javelle and al, 2010) It is a simple event-based distributed hydrological model transforming rainfalls into discharges. The evaluation of the model quality is always a delicate task when no data are available (ungauged basins). Two ways are explored to evaluate the AIGA method performance on different small catchments located on a 17000 km² area on the South of France. On the one hand, the real-time RHYTMME platform is used. For each important storm event, the platform end-users composed by different public services (like “Restoration of Mountainous Territories (RTM)) realize an on-field survey. This users group tests the platform in real-time. The rainfall is estimated by the X-band radar and the calculated discharges are compared to damages reported by end-users. On the other hand, in order to improve the AIGA method, an historical data-base of flood damages reports, covering the 1997-2006 period, is used. These data have been collected by local authorities (RTM) and give us some information on 139 ungauged locations. Using radar rainfall data provided by METEO-FRANCE for the 1997-2006 period, the discharges are modelled and compared to these observed damages.. We are then able to evaluate, for each watershed, a threshold discharge above which most damages occur. The main advantage of this historical approach is the availability of many events in the data-base, which enabled us to calibrate the threshold discharges thanks to the optimisation of a contingency criterion (the CSI index).
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Dates et versions

hal-01886155 , version 1 (10-10-2018)

Identifiants

  • HAL Id : hal-01886155 , version 1

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Dimitri Defrance, Stéphane Ecrepont, Pierre Javelle, Catherine Fouchier, Vazken Andréassian, et al.. THE “RHYTMME” PROJECT IN MOUNTAINOUS AREAS USING X-BAND WEATHER RADARS: SOME PRELIMINARY RESULTS OBTAINED FOR FLASH FLOOD WARNING. 4rd IMPRINTS Workshop, Sep 2012, Bruxelles, Belgium. ⟨hal-01886155⟩

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