Contribution à un modèle d’adaptation des villes sahariennes au phénomène d’ensablement

Abstract

For decades, we have been worried about the extent of silting phenomenon in desert area. Concerning the Algerian case of the Gourara area, different projects have been multiplied to try, without success, to stem the inexorable evolution of the phenomenon. Solutions such as planting trees or developing the “afreg-dune”are adopted; however, they seem to be simplistic thus are seen as a partial approach to the problem. The silting occurs insidiously and latently from a single obstacle put in place in the direction of prevailing winds. Any impact on wind silting movements should be investigated to put forward the necessary safeguards to achieve protection from silting in any development or construction. In this context and through this research, we propose to accompany architects and urban planners to the rank potential actions in mitigating silting phenomenon. The principle of an adaptation model we propose is to guide, not to direct the development actors through a proposed set of rules in terms of planning and design of built forms adapted to the silting phenomenon, according to three levels of intervention: First at a macro scale, we predict “preventing”rules. We have tried to identify and classify areas according to their degree of exposure to the risk of silting based on relevant elements namely, in site characteristics, such as topography, soil and dunes types, and wind regime. Recommendations and guidance in terms of development have been drawn up for the various areas identified. Second, at a meso and micro scale, we recommend “protection”. This concerns, except mechanical and biological control, the aerodynamic whose goals is to promote the thrust of the sand grains in saltation movement to fight against deposits inside of the master plan. Through CFD modeling, we managed to establish a set of reports for dimensional models of buildings and urban forms incorporating aerodynamic effect such as the Venturi and Channelling effects. The positive impact on improving the flow of air in the developed models has been proven and validated by calculating the sediment budget via mathematical simulation experiments.