Les aléas naturels en zones urbaines semi-arides – Étude de cas de Boussaâda (Algérie)

The study aims to emphasize the hazard diversity in the warm semi-arid climate areas, beginning from the concrete analyze of the Bou-Saada city (Algeria). Bou-Saada is situated at the contact of the Hodna shot with the Presaharian Atlas in the proximity of a corridor, which allows the orientation of the air masses. The extinction of the city has lead to the partial destruction of the oasis, as well as the exposition to the different risk phenomena, being frequent the following: - The exposition to the sand accumulation, especially of the district developed on the Southern-Western corridor, in the wind direction; - The exposition to the rock falls from the mountain side, in the conditions of a powerful desegregation; - The exposition to the inundations during the rare torrential rains, being also facilitated by the city development in a narrow depression, which allows quick running of water from the mountain side. The main factors determining the quality of the geomorphological vulnerability to the hazards (geological, geomorphological, climatic, anthropogenetic, biopedogeographical) highlight the favourability of the position of the first nucleus of the settlement compared to its area of current expansion. The research was made in many campaigns between the years of 2006-2008, within an agreement of cooperation, being in progress.