Search

Nowadays, urban sprawl is one of the major problems facing the Algerian Low-Sahara oases. Monitoring and understanding its spatial evolution remains an essential step for any sustainable development project of the oasis city. Local authorities do not have relevant and updated tools for effective management and spatial planning. Remote sensing and Geographic Information Systems (GIS) provide opportunities to overcome these difficulties. The present study consists in application of a change detection technique to map and quantify the spatiotemporal sprawl of Biskra City (Algeria), during the period 1985 - 2000, using three Landsat images acquired in 1985, 2000 and 2015. The post-classification comparison of land use and land cover maps has revealed a remarkable growth in the built-up areas going beyond the municipality's boundaries, in conurbation with the agglomeration of Chetma, against a progressive decline of the palm grove. It has undergone a continue process of fragmentation and conversion of its surface by the uncontrolled urbanisation, leading to the loss of the original oasis identity distinguishing this city. The main aim of this paper is to highlight the urban sprawl process and its spatial land use and land cover modifications. This study also shows the utility of change detection methods and Geographic Information Systems for monitoring the urbanisation patterns and assessing their impacts on oasis ecosystems. [ABSTRACT FROM AUTHOR]

Slope instability phenomena, by their essentially random nature, generate risks for various elements of mountain heritage. In Man Mountains region of Man, located in the west of Côte d'Ivoire, the manifestation of these phenomena is made more and more because of the rugged terrain and climate change. This study aims to map potential areas of slope instability movements in the Man area to prevent natural damage and/or casualties. The method used in this work, is based on remote sensing, Geographic Information System (GIS) and Saaty's analytic hierarchy process (AHP) method. Six (6) factors involved in the occurrence of landslides such as slope, drainage density, fracturing density, regolith thickness, precipitation, and normalized vegetation index (NDVI) have been mapped. Their integration into a GIS has made it possible to map the region's susceptibility to slope instability movements. Indeed, using Saaty's analytic hierarchy process (AHP) method, a prioritization, a weighting and a classification of the different factors were made. This facilitated the linear combination of the different factors in the GIS. The resulting susceptibility map was field-verified to yield a susceptibility map to slope instability movements of Man area. This map shows classes of very low, low, moderate, high and very high susceptibility. Areas of high and very high instability represent 14.65%. They are located in the West Central of the study area. Majority of these areas are found on the slopes of the Tours and Dan, mountains located between Biankouma and Man, which are characterized by steep slopes and registrate rainfall of more than 1500 mm. [ABSTRACT FROM AUTHOR]

This paper aims to establish a map of the flood risk of the coastal plain of Saïdia located on the Mediterranean coast of north-eastern Morocco. This plain is enclosed between rivers : the Moulouya in the West and the Kiss in the East. It is bordered to the south by the Ouled Mansour Mountains. These are sheared by very steep ravines that empty directly into the plain. The groundwater is very shallow. This background coupled with geomorphic coastal development promotes the current flood risk. In this paper, the methodology is based on the structuring in a geographic information system (GIS), remote sensing data, products derived from a digital elevation model (DEM) and external data (lithology, the groundwater level, etc.). The analytical approach consists of a digital processing of a GeoEye-1 satellite image and aerial photographs to map the surface states, an extraction phase of topographic attributes and geomorphology of the land, represented by the digital elevation model (DEM) and a phase of structuring information for spatial analysis in a GIS. These investigations allowed the construction of two maps : the map of vulnerability to flood and the map of hazards. The vulnerability map shows that very high vulnerability areas represent 57% of the site and correspond to areas of inter-dunes flat formed by deposits of fine clay, and characterized by lowland sector (0-4 m). The hazard map refers to the land cover. The superposition of these two maps helped to establish the map flood risk. This thematic map shows that approximately 43% of the territory considered is located in high to very high flood risk areas, and correspond to the banks of the Moulouya and the kiss rivers and to the marshes of the Moulouya River, and to the sector on which the new Saidia resort is built. [ABSTRACT FROM AUTHOR]