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Abstract: The assessment of seismic risk in northeastern Algeria is one of the main challenges for the region’s development. Seismic risk evaluation is based on the identification of active structures and the tracing of seismic faults. This approach faces a number of obstacles, including the complexity of the geological context, the weakness and imprecision of present geo-cartographic data, the predominance of argillaceous facies and the degradation of morphological expressions of deformation. Remote sensing is a valuable technique not only for the detection and cartography of active faults, but also for seismic risk management and the integration of these risks into sustainable development projects and territorial planning. In this study, we applied two remote sensing techniques: firstly, we have used optical image correlation. This correlation is performed between two images from the Sentinel 2A satellite, in descending mode, acquired at different times, before and after the earthquake. Secondly, we have used interferometric synthetic aperture radar (InSAR) which is based on the phase comparison of two SAR (synthetic aperture radar) images, used to construct the “Single Look Complex SLC” interferogram, from the Sentinel 1B satellite which were acquired at different times, but with similar acquisition geometries, covering the same area on the ground surface. The main objective of this study is to cartography and calculates the co-seismic displacements in our study region.
Abstract: The urban area estimation in dry and semi-dry climate, is still a difficult. Therefore, identify a reliable impervious index is critical. For that reason, Ain Azel city that located in semi-arid land of North-East Algeria, was the area of test of three impervious indices, namely: the Built-up Area Index (BAI), the Normalized Impervious Surface Index (NISI) and the Urban Area Index (UAI). These indices were derived from Sentinel-2 data and subjected to the Support Vector Machine (SVM) classification method, to extract built-up area class. The accuracy assessment results showed that the Overall accuracy (Oa) of the NISI index achieved 92,67 %, which is a little less compared to the (Oa) of UAI index which is about 93.67 %. Based on this, the both indices provided satisfactory result, although the UAI index, relatively, overestimated the built-up area. However, the BAI index that use the Blue and Near-Infrared bands is sufficiently discriminative between highly similar of buildings materials and dry soil; the BAI index produced the accurate built-up mapping with well detection of road networks with (Oa) achieved 95.67% and the highest kappa coefficient which is about 86.54 %. This is due to BAI band’s degree of sensitivity and their high spatial resolution of 10 m. Consequently, the SVM segmentation-based BAI index worked well and the result is promising for accurate modeling of cities with same environment condition, for its sustainable development. However, the performance level evaluation of indices applied in this study, should be retested over different regions in dry land.
Abstract: Walkability, as a fundamental concept of active mobility, plays a crucial role in improving the quality of life in urban environments. This article aims to examine thoroughly the impact of urban morphology on pedestrian mobility, by analyzing the urban form of the Colonne neighborhood located in the city of Annaba, Algeria. Two approaches are used in this research: a quantitative approach using the Walkability Index, supported by the International Physical Activity and Environment Network (IPEN) project, and a qualitative approach based on a field questionnaire survey. The four variables within the Walkability Index are assessed using a Geographic Information System (GIS) to classify them individually. The results are then compared across zones and street segments most frequented by the respondents , according to the survey. The comparison explicitly reveals a strong positive correlation between the Walkability Index values and people’s tendency to walk. Moreover, the two main streets record the highest walkability values and are the most frequented throughout the neighborhood. This confirms the idea that walkability and levels of outdoor physical activity are strongly influenced by the urban morphology of the neighborhood. These results support the hypothesis that there is a strong relationship between urban morphology and walking practices within urban spaces. Further evaluation of other neighborhoods in Annaba, with varying urban morphologies, could enrich the understanding of walkability across the region.
Abstract: This study aims to identify regions prone to desertification in the Hodna basin, which covers a vast area of the vulnerable Algerian Steppes. Thirteen factors were selected as independent variables: geomorphological factors (wind and water erosion, Topographic Position Index (TPI), Drainage Density, Slope, Aspect, Elevation), environmental factors (Normalized Difference Vegetation Index (NDVI) and Evapotranspiration), soil factors (Land surface Temperature (LST) and Normalized Difference Salinity Index (NDSI), and socio-economic factors (the Human Influence Index (HII) and the Livestock. Due to the lack of previous desertification data, NDVI anomalies served as the dependent variable. all of the variables were mainly derived using remote sensing techniques and a logistic regression model was applied for analysis in the R environment for desertification susceptibility mapping, displaying stable predictive power with a Receiver Operating Characteristic (ROC) curve of 0.76. Unlike the Northern part of the Mediterranean, where water erosion is predominant, wind erosion and soil salinization emerged as key factors in this study, while the socio-economic factors had less influence than anticipated. The resulting map shows that 45.4% of the basin is highly to very highly susceptible to desertification, provinding essential data for targeted intervention strategies.
Abstract: Floods are considered one of the most significant natural threats to cities and their infrastructure, especially when urban resilience is weak of floods, due to both human and natural factors. This is the case in the Algerian city of Tebessa, where urban resilience is low in the watershed of Wadi Nagues, which divides the city from north to south. Informal expansion along the riverbanks and inadequate city infrastructure increases the risk of flooding in the city. This study aims to identify the factors that increase flood hazards in Wadi Nagues and analyze maximum daily rainfall values to determine the maximum flood flow and volume during different return periods of 10, 50, 100, and 200 years, in order to map the floodplain of the river. This is accomplished using Geographic Information Systems (GIS) and HEC-RAS software for flood simulation. The results of the flood simulation in Wadi Nagues show that river waters inundate the southern areas of informal expansion, the airport, the railway, Houari Boumediene neighborhoods, and the Constantine Road – which is an economic artery for the city. The peak flow reaches 86.82 m³/h, and the volume of flow is 159.20 m³/s, in a during a 200-year return period. Field surveys also reveal several other human factors that increase the risk of flooding, such as informal expansion, lack and weakness of flood protection hydraulic structures, and poor river water cleanliness. This necessitates intervention to protect the city from flood hazard.
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