The use of Geographic Information System for the Assessment of Geotechnical Risks in Madagascar

Abstract

The Upper City of Antananarivo, is one of the districts of the capital of Madagascar subject to the regulations of the Architectural, Urban and Landscape Heritage Protection Zone [1]. On the other hand, the urbanization of this zone has not made it possible to curb the uncontrolled urbanization which is characterized by the spontaneity of illicit constructions caused in particular by the impoverishment of the local populations. Faced with this situation, the sanitation aspect of the area is no longer under control and all these phenomena have created a new type of exposure to risk through the degradation of the supporting soil and the triggering of fatal land movements. This urbanized area is subject to geotechnical risks that require reconnaissance on geological structuring, urbanization and problems observed to monitor the evolution of hazards. Technical studies of the Antananarivo upper town massif reveal instability and eventually hazards such as landslides, rock falls and block falls. These rapid phenomena expose local populations to new risks. As such, the consideration of risk management in this area and its mapping using Geographic Information Systems (GIS) is vital. The objective of this paper is to draw up maps of urbanization and geotechnical hazards in the area concerned in order to monitor the evolution of risks and to alert the populations to the danger that may occur. Results of the research will provide operational solutions, especially in the decision-making process of local authorities regarding the evolution of these hazards and the sporadic evolution of housing in the upper city of Antananarivo, leading to the implementation of a continuous monitoring system, with alarm triggering on threshold detection the Early Warning