Abstract
Abstract Relationships between geomorphic structures and hydrological processes during storms are studied in the Agly catchment (1 045 km2). This basin is located in the eastern part of the French Pyrenees. The channel network is influenced by structural landforms. High order streams are oriented according to the main east-west trend of faulting and folding. These tectonic features are inherited from the pyrenean uplift partly eroded, and then rejuvenated during the mio-pliocene period. This context, combined with the local mediterranean climate, leads to heavy flood occurrences especially during storm events. Two approaches are followed : simulation of stream flow on gauged basins and analysis of the evolution of floods hydro- graphs along the main river, during a heavy storm. Morphometric characteristics of several sub-catchments are used for the study of their effects on runoff and river flows. Simulations of river flows from Digital Elevation Models (D.EM.) are compared with observed storm flows. Results of the simulation are accurated for time to peak flow. The general shape of the simulated hydrograph reflects the geomorphometric characteristics of the catchment basin. The flood associated with a storm lasting about 3 hours on September 26 , 1992 is depicted at five gauged stations along the main stream of the Agly river. The speed of the flood wave for this storm was quite fast (3 meters/sec.) and this justifies the flood warning equipment of this catchment. More comprehensive research must be conducted to emphasize hydrological processes understanding via geomorphological approach. Global understanding of how catchment basins work is required to face such natural hazard as floods. Geomorphologists have to be involved in this challenge.
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