Mode of Habitation Architectural in the City of Toliara, (Southwest- Madagascar), Factor of Exposure to the Risks of Hydroclimatic Hazards

The housing problem is a universal phenomenon that mainly affects developing countries. Toliara, a city in southwestern Madagascar, is located in a delta. The low elevation of the land is one of the inherent causes of     flooding due to the rise of the river and marine submersion. In addition, the method of housing construction and the materials used have further weighed down urban ones. The cartographic approach based on the analysis of maps and satellite photos combined with the field survey method made it possible to assess the dominance of a habitat that does not support the submersion of runoff water and the intensity of the wind. The qualitative and quantitative analysis of the habitats shows the profile of the districts in the dominance of the precarious habitats only on the whole of 72890 inventoried constructions, 39453 are of precarious habitats, and only 33437 are solid constructions (low and story house). Only downtown, with a checkerboard urban plan from 1901, we can see a dominant solid housing, resistant to climatic disturbances. On the other hand, the outskirts have a dominant plant habitat (rush, wood) and corrugated sheets which is very fragile in the face of extreme floods. The rapid spread of the city has a significant impact on urban planning. The strong reception of rural immigrants (Tandroy, Mahafaly, Tagnalagna) since the colonization (1925) to the present day, the economic decline of the population, and the attachment to rural customs and cultures in the urban environment have greatly contributed to the exhibition of Toliara to hydrological hazards.