Contribution d'un bassin versant élémentaire cultivé à la formation de crues/Contribution of an elementary cultivated watershed to flood generation

Abstract

The studies carried out by the authors for several years, concerning runoff and erosion in temperate plains and hills environments, allow to understand floods formation in large farmlands. The studied watershed belongs to the Laonnois hills domain where the slopes in « glacis »form are relatively steep (3-6 %) with small contributing areas. On these sites, several rainfall and runoff records are relevant to perceive and to explain floods formation which generate severe environmental and economical damages in the region. Links between climatic data (i.e. quantity, intensity and periodicity of rainfalls) and physical soil data (i.e. moisture, structure) were established in relation with man activity (soil occupation, agricultural practices, particularly machinery weight provoking infiltration decrease and available water mass increase). These data allow to establish a quantitative and qualitative budget model showing how modern agriculture interferes on the circulation of liquid and solid discharge in large farmlands. This analysis puts forth a better management for rural areas in order to reduce damages caused by this event; it is also an attempt to draw up a typology for the regions affected by risk potentialities.