Dynamique des versants et milieux naturels

Abstract

Abstract. For long, maghrebine geographers have analysed existing relations between the degradation of nature, slope dynamics and decisive part. Three features can be distinguished in the explanation of these phenomena ; the degradation of the media results from the worsening of the climate, and men only accele rate this irreversible process (J. Pouquet, 1952) ; the disappearing of primary vegetation with the use of the land involves series of mechanisms, also irreversible, towards slope-degradation ; others, agreeing with this anthropic explanation, consider it as recent process due to colonization. A detailed geomorphological mapping of the Soummam valley enables the author to weigh each of these explanations in the case of Grande Kabylie. The analysis of three examples taken in different areas of the lower Soummam valley, leads to put the stress on the part played by rural abandonment in the evolution and the dynamics of slopes. In many cases, recent evolution of morphogenetical media towards instability is in tight relationship with rural abandonment and the neglect of traditional agricultural practices ; this abandonment of land is often bound to rural exodus. These observations involve new methods in the field of river-basin reclamation Short-scaled general thematic surveys must be done along with studies of slope-dynamics and socio-economical features in typical areas.