Geochemical characterization the waters of Foggaras the Continental Intercalary Aquifer of Timinoune region (south west Algeria)

The study of the Continental Intercalary (C.I) groundwater of the region of Timimoune (southwestern Algeria), based on physico-chemical data (major elements), allowed to understand the geochemistry of foggaras water. The aquifer is contained in the formations of the Lower Cretaceous (Albian and Barremian). The waters are strongly mineralized with an average value 2g / l.The waters have a clear predominance of facies chlorinated-sodium. The risk is high to excessive soil salinization, and the risk of medium alkalinity to very high. Statistical analysis led us to reach two conclusions, the first is that, variable electrical conductivity (EC), dry residue (RS), Na+, Ca2+, Cl-, SO4 --, mineralization, are best correlated and responsible the signing of the mineral load of water, the second is that the nitrate ion (NO3-) opposite to the above-mentioned variables mark its anthropogenic origin. Keywords: Continental Intercalary, mineralization, salinity, PCA, Nitrat

Utilisation des SIG pour l’aménagement du bassin-versant de l’ISSER (Algerie)

Situé au nord-ouest de l’Algérie, le bassin versant de l’Isser, espace fragilisé par les épisodes de sécheresse et caractérisé par des affleurements de marnes et d’argiles très fragiles, présente une forte sensibilité à l’érosion hydrique. En plus de la détérioration de la qualité de l’eau qu’il entraîne, le phénomène érosif dans cette zone, constitue l’accusé principal de la dégradation du patrimoine sol. Il résulte de la conjonction de plusieurs facteurs : agressivité des pluies, érodibilité des sols, dissection du relief, faiblesse du couvert végétal…La reconnaissance des zones ravinées et la précision des caractéristiques climatiques et hydriques de la zone d’étude, peuvent servir de base à l’élaboration d’un plan d’aménagement antiérosif adapté aux conditions du milieu.Pour ce faire, une carte de localisation des zones à haut risque, au niveau du bassin versant, correspondant au croisement d’une série de cartes thématiques, a été établie. Cette carte permet de mettre en évidence les zones nécessitant un aménagement prioritaire. La synthèse de l'ensemble des résultats sous un système d’information géographique (SIG), nous a encouragés à proposer des travaux d’aménagement antiérosifs techniques (correction torrentielle) et biologiques (reboisement), visant à atténuer les effets négatifs des pertes en terre aussi bien à l’amont qu’à l’aval. Le choix des ouvrages et les décisions à prendre doivent être fondés sur l’action des facteurs biophysiques et anthropiques. Par ailleurs, ces travaux doivent s’intégrer dans une nouvelle stratégie visant une meilleure gestion de l’espace dans une optique de développement durable, en tenant compte des besoins et des perspectives de la population rurale.Located in Northwest Algeria, the watershed of Isser is an ecosystem weakened by drought episodes and strongly sensitive to water erosion.Erosive phenomenon, in this ecosystem, is the result of a combination of several factors : aggressiveness of the rains ; erodibility of the soils (marls) ; stiffness of the relief, weakness of the vegetal cover.Localising the gullied zones and specifying the climatic and hydric characteristics of the study zone are prerequisites to the development of any sustainable erosion control strategy.The overlaying of a series of thematic maps, fed into a Geographical Information system (GIS), has led to the design of a map localising the gullied zones in the watershed requiring restoration works, first and foremost. The antierosive operations suggested include technical measures (torrential corrections) as well as biological measures (reforestation).Such erosion control measures should however be integrated into a program whose main objectives should be a better management of water and soil resources taking into account the expectations and needs of the rural population

Spiking neuron network for image segmentation

National audienceThe process of segmenting images is one of the most critical ones in automatic image analysis whose goal can be regarded as to find what objects are presented in images. Artificial neural networks have been well developed. First two generations of neural networks have a lot of successful applications. Spiking Neuron Networks (SNNs) are often referred to as the 3rd generation of neural networks which have potential to solve problems related to biological stimuli. They derive their strength and interest from an accurate modeling of synaptic interactions between neurons, taking into account the time of spike emission. SNNs overcome the computational power of neural networks made of threshold or sigmoidal units. Based on dynamic eventdriven processing, they open up new horizons for developing models with an exponential capacity of memorizing and a strong ability to fast adaptation. Moreover, SNNs add a new dimension, the temporal axis, to the representation capacity and the processing abilities of neural networks. In this paper, we present how SNN can be applied with efficacy in image segmentation

Multisource data integration to investigate a 3D landslide morphology affecting an urban area: case of Bordj Bou Naama (west Algeria)

Situated in the northern part of Algeria, Ouarsenis is one of several area affected by landslide phenomena. Indeed, 60 houses, a stadium and a lot of sports infrastructures are affected by the landslides. In this perspective, we have chosen a model of landslide with an area of 166 700 m2 affecting the southern part of the Bordj Bou Naama city. In order to characterized the landslide structure, we used multisource data (geological, topographical, geophysical and geotechnical). For modeling the 3D landslide surfaces we used three geometric models which are generated from different techniques of interpolation as Inverse Distance Weight (IDW), Minimum Curvature (MC) and Kriging (KO) and applied to the same input data set. The root of the mean square error (RMSE) and visual appearance of the morphology are used to select the best model. Indeed our results show that the KO represents the best model that gives a good result. Quality control is also performed to ensure that the model is suitable for hydro-mechanical modeling. This model show that the total volume of soils moved is ~9.8*105 m3, in which the volume of geological levels is 828 500 m3, 143440 m3 and 11 434.32 m3 respectively for the embankments, colluviums and Brown shale. The bleu shale is far from to be affected by this landslides, indeed the deepest zone that the rupture area affects is located at 12 m of depth. These results seem to be very important in order to plan remediation work in this area

Neotectonic deformation stages in the central Ouarsenis culminating zone, Northwestern Algeria

International audienceThe Tellian system in the north of Algeria results from the convergence of the African and Eurasian plates which began in the Late Cretaceous. The strong tangentional tectonics at the origin of the emplacement of nappes in its external domain occurred mainly during the Early Miocene. This major tectonic episode was followed by another important compressive deformation-oriented NNE-SSW and NNW-SSE during the Pliocene and the Quaternary, respectively. The Ouarsenis culminating zone is part of the Tellian domain and is characterized by an altogether distinct orographical structure made up of: (i) Jurassic formations which overthrust Cretaceous terrains; (ii) completely upturned series; diversely oriented faults (N40°, N70°, N120°, and N160°) of different kinds (thrust, reverse, normal, and shear faults). Triassic gypsum crops out along some of these faults. Microtectonic data analysis has shown alternation of two main compressive stresses, NW-SE and NE-SW oriented. The more recent stress, probably of Pliocene age, ∼N56° oriented, is responsible for the current face of the culminating zone. It highlights a major ∼N120° sinistral shear fault-generated deformation especially in its central part, affecting ductile material represented by Albo-Aptian turbidites. This fault also generated secondary shears accommodated according to a Riedel deformation model. The central part of this area has a complex tectonic structure squeezed between two massifs composed of hard material, along the sinistral shears. It has been extruded towards the north and has evolved as a positive “flower structure.

Lutte antiérosive

Face à la pression démographique et foncière dans les pays en développement, la productivité des terres connaît actuellement une forte baisse dans de nombreuses régions tropicales. Par ailleurs, la succession rapprochée des tempêtes cycloniques entraîne l'appauvrissement extrême de certaines populations du fait de la dégradation des terres et des inondations des plaines où se développent les principales agglomérations. Telles sont les problématiques étudiées par l'IRD et le réseau Érosion de l'AUF dont ce CD présente les derniers travaux. Initialement réunies dans la perspective d'un colloque à Haïti (annulé suite au séisme de 2010), les contributions publiées ici portent sur des études de cas à Haïti, mais aussi à Madagascar, au Maghreb ou au Vietnam, soit au total une soixantaine de communications et une série de documents récents issus des réflexions des experts. Structuré en six thèmes, ce CD constitue ainsi une source bibliographique précieuse pour les décideurs, les experts, les ONG, les acteurs de la société civile et les chercheurs concernés par la gestion durable de l'eau et la restauration de la productivité des sols (GCES)