Etude du rôle hydrologique d'une tourbière de montagne: modélisation comparée de couples "averse-crue" sur deux bassins versants du Mont-Lozère

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Cognard-Plancq, Anne-Laure ; Bogner, Christina ; Marc, Vincent ; Lavabre, Jacques ; Martin, Claude ; Didon-Lescot, Jean-François:
Etude du rôle hydrologique d'une tourbière de montagne: modélisation comparée de couples "averse-crue" sur deux bassins versants du Mont-Lozère.
In: Etudes de Géographie Physique. Bd. 31 (2004) . - S. 3-15.
ISSN 0769-1750

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Abstract

The impact of a toeslope humid area upon high flows was studied in a sub-Mediterranean mountainous catchment (Peschio catchment, Mont-Lozère) using a lumped rainfall-runoff model (GR3H).The simulations were carried out at a hourly time step. The model performances and parameters werecompared with those computed on an adjacent bog-free catchment (Samouse catchment) used as reference.From the study of 24 flood events recorded between January 2000 and December 2001, the overall qualityof the simulations was found to be better for the reference catchment : 1 and 9 bad fittings for the Samouse and Peschio catchments, respectively. The shape of the instantaneous unit hydrographs corroborated the results from previous study : the humid area induces a delay in the catchment response and smoothes the flood event. However, this behaviour is subdued to a seasonal evolution, with a gradual increase of thecatchment lag time while the bog dries up. Thus, the lag time on Peschio varied from 2 hours in winter to 14 hours in august 2000. By comparison, the lag time on the reference catchment kept values close to 1,5 h.