Abstract
Through the study of unities which constitute the alluvial plain, the hydrogeomorphological method allows to delimit easily the stream's liable-to-flooding areas. The object of this thesis is to contribute to the improvement of the method. A chapter is dedicated to the understanding of the hydrodynamics processes of the functional alluvial plain. A hydrological reality is given to the unities which constitute it, to better defined the hazard which is linked to its. Through examples of Orbieu and Ouvèze, the presence of intermediate flow channel and bank separating the different beds, on Mediterranean rivers was justified. A second chapter develops examples taken on Argent-Double, Orbieu, Bayon, Gardon, Cèze and Ouvèze, from which a typology of the different contacts between the liable-to-flooding areas and the embankment was established. Exceptional floodplains and holocene terraces were characterized and a cartographic translation is proposed in agreement with graphic semiology and constraints necessary for the elaboration of the official documents like French risk prevention plans of floods (PPRI) and atlases of liable-to-flooding areas (AZI). Their study brings complements to the chronology of the evolution of river hydrosystems in recent Holocene.