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Du drain potentiel au drain réel : utilisation de données satellitales à très haute résolution pour l’étude de l’origine géomorphologique des chemins de l’eau sur des bassins versants méditerranéens soumis aux crues éclair.

Abstract : In Mediterranean areas, heavy rainfalls can generate flash floods during fall season. The rainfall intensities and their high spatial variability combined with complex processes of run-off generation reduce drastically the predictability of these phenomena. Although rainfall intensities monitoring techniques are progressing, another way to better understand and predict the hydrological responses of the catchments is to better understand the hydrological processes underlying the spatial and temporal variability of water pathways on upstream elementary catchments where concentrated flows begin. In the framework of spatial hydrology, this PhD proposes to study the potentialities of remote sensing, in particular the emergent high spatial resolution 3D products, to characterize catchments drainage elementary networks in order to relate some derivated geomorphologic traits to the observed hydrological responses all over catchments. This permits to identify the involved hydrological processes during flow dynamics on upstream mountainous catchments. This work is organized in two axes. The first one consists in characterizing, from 3D satellite data, the “potential” drain corresponding to the dry morphological network of a basin, formed by the continuum of thalweg lines within a catchment. An original algorithm, based on a TIN DEM structure, has been specifically designed for this purpose. This algorithm allows the delineation of thalwegs networks and provides geomorphological traits of catchments and networks. The second axe concern the study of the spatial dynamic of the “real” drain, which is the drain with effective flow. The goal is to enhance the understanding of flow networks spatial dynamics during rainfall events. A specific sensor network has been specially distributed on two experimental sub-catchments of the Gardon d’Anduze watershed in order to monitor the spatio-temporal variations of flow and network dynamics. The relationship between computed geomorphologic features and observed hydrological responses along networks tends to confirm the prevalence of sub-surface flows on the studied catchments. This exhibits two types of hydrographic networks, showing two distinct hydrological behaviors (the principal and secondary networks). Results also show the great influence of slopes and their variations on flow initiation and durability, and to propose hypothesis of hydrological mechanisms, in function of the observed events.
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https://tel.archives-ouvertes.fr/tel-00715931
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Submitted on : Monday, July 9, 2012 - 3:12:23 PM
Last modification on : Wednesday, June 24, 2020 - 4:19:07 PM
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  • HAL Id : tel-00715931, version 1

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Denis Maréchal. Du drain potentiel au drain réel : utilisation de données satellitales à très haute résolution pour l’étude de l’origine géomorphologique des chemins de l’eau sur des bassins versants méditerranéens soumis aux crues éclair.. Autre. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2011. Français. ⟨NNT : 2011EMSE0609⟩. ⟨tel-00715931⟩

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