Regionalisation of the “intensity-duration-frequency” curves in Northern Algeria

The flood events observed during last years in the urban areas are subject of main interest for quantification of the hydro-climatic risks and climatic change to the regional scales. The establishment of a statistical relationship between the intensities of intense rains and the recurrence of these events allows us to determine the dimensions of the works according to a previously defined level of risk. They constitute today a leading tool for various users. This work concerns the study of the maximum annual rains, recorded at 49 stations in the northern Algeria. The objectives of this work are to determine the estimators who are the “intensity-duration-frequency” curves and to extract from these whole of information the b Montana climatic parameter to be regionalized for the calculating the river flow and for the dimensioning of the networks of cleansing in the event of insufficiency of data. Different durations going from 15 min to 24 h are studied. We utilised the collocated co-kriging as multivariate estimation method for interpolation in order to yield the space distribution maps of b Montana climatic parameter, with the benefit of using spatially correlated secondary variables, such as the digital elevation model and the distance from the coastline that are known at any localisation. All features led to choose the digital elevation model as covariate for interpolating b Montana values, yielding a better regionalisation of the studied climatic parameter. The geostatistical handling of b Montana values strictly related to auxiliary variables that constitute physical factors overcomes the data shortage in planning, managing and preventing the rain flood risk.     

Laboratory Study of Air Sparging: Air Flow Visualization

Laboratory flow visualization experiments, using glass beads as the porous medium, were conducted to study air sparging, an innovative technology for subsurface contaminant remediation. The purpose of these experiments was to observe how air flows through saturated porous media and to obtain a basic understanding of air plume formation and medium heterogeneity effects. The experiments indicate that air flow occurring in discrete, stable channels is the most probable flow behavior in medium to fine grained water saturated porous media and that medium heterogeneity plays an important role in the development of air channels. Several simulated scales of heterogeneities, from pore to field, have been studied. The results suggest that air channel formation is sensitive to the various scales of heterogeneities. Site-specific hydrogeologic settings have to be carefully reviewed before air sparging is applied to remediate sites contaminated by volatile organic compounds.     

Morphological evolution of center Boumerdes in Zemmouri Bay (Algeria) from 1922 to 2017

The morphological evolution of shallows seabed has undergone great changes over the past 95 years. These changes have not only led to the decreases of water volume but also to the spatial variability of sediments. However, the distribution and the movement of marine sediments from underwater beaches are very complex due to the combination of several factors such as hydrodynamic factors (e.g., tidal currents ±?34 cm, swells and currents driven by the prevailing northeast wind), and entropic factors (e.g., soil occupation and protective installation of structures as breakwater, groynes, retaining wall). This situation can disrupt the sedimentary regime in the Boumerdes area. In order to better understand the hydrodynamic processes, the recognition of sedimentary processes, the modalities, and erosion mechanisms of this zone are necessary. Thus, the study of long-term underwater morphological evolution by comparing between the bathymetric surveys of different years, between 1922 and 2017, is required to study the feasibility of coastal engineering projects. The seabed bathymetric evolution of this coastal fringe from erosion point of view was appreciated. It is based on a geographic information system (GIS), which allows to carry out a digital depth model interpolated by kriging method.     

Geochemical characterization of the salinity of irrigated soils in arid regions (Biskra,SE Algeria)

Acta Geochimica - The agriculture in Biskra, southeastern Algeria, is based on traditional practices and characterized by small irrigated fields. In the last decades, the increasing demand in water...     

Landslide susceptibility mapping using analytic hierarchy process and information value methods along a highway road section in Constantine,Algeria

This research work deals with the landslide susceptibility assessment using Analytic hierarchy process (AHP) and information value (IV) methods along a highway road section in Constantine region, NE Algeria. The landslide inventory map which has a total of 29 single landslide locations was created based on historical information, aerial photo interpretation, remote sensing images, and extensive field surveys. The different landslide influencing geoenvironmental factors considered for this study are lithology, slope gradient, slope aspect, distance from faults, land use, distance from streams, and geotechnical parameters. A thematic layer map is generated for every geoenvironmental factor using Geographic Information System (GIS); the lithological units and the distance from faults maps were extracted from the geological database of the region. The slope gradient, slope aspect, and distance from streams were calculated from the Digital Elevation Model (DEM). Contemporary land use map was derived from satellite images and field study. Concerning the geotechnical parameters maps, they were determined making use of the geotechnical data from laboratory tests. The analysis of the relationships between the landslide-related factors and the landslide events was then carried out in GIS environment. The AUC plot showed that the susceptibility maps had a success rate of 77 and 66% for IV and AHP models, respectively. For that purpose, the IV model is better in predicting the occurrence of landslides than AHP one. Therefore, the information value method could be used as a landslide susceptibility mapping zonation method along other sections of the A1 highway.     

Modelling coincidence and dependence of flood hazard phenomena in a Probabilistic Flood Hazard Assessment (PFHA) framework: case study in Le Havre

Many coastal urban areas and many coastal facilities must be protected against pluvial and marine floods, as their location near the sea is necessary. As part of the development of a Probabilistic Flood Hazard Approach (PFHA), several flood phenomena have to be modelled at the same time (or with an offset time) to estimate the contribution of each one. Modelling the combination and the dependence of several flooding sources is a key issue in the context of a PFHA. As coastal zones in France are densely populated, marine flooding represents a natural hazard threatening the coastal populations and facilities in several areas along the shore. Indeed, marine flooding is the most important source of coastal lowlands inundations. It is mainly generated by storm action that makes sea level rise above the tide. Furthermore, when combined with rainfall, coastal flooding can be more consequent. While there are several approaches to analyse and characterize marine flooding hazard with either extreme sea levels or intense rainfall, only few studies combine these two phenomena in a PFHA framework. Thus this study aims to develop a method for the analysis of a combined action of rainfall and sea level. This analysis is performed on the city of Le Havre, a French urban city on the English Channel coast, as a case study. In this work, we have used deterministic materials for rainfall and sea level modelling and proposed a new approach for estimating the probabilities of flooding.

     

Typologie et mode de mise en place des roches magmatiques dans les Pyrénées hercyniennes

Résumé L'évolution géodynamique hercynienne des Pyrénées se caractérise par une importante activité magmatique à l'origine de corps plutomques de taille, de composition et de niveaux de mise en place différents. A partir de ces caractéristiques nous avons pu établir une typologie qui nous a permis de distinguer deux types principaux de massifs: 1) les massifs de composition homogène, acides (massifs de type HA) ou basiques (massifs de type HB), localisés dans les grands ensembles métamorphiques régionaux et 2) les massifs de composition hétérogène, formés par l'association de roches basiques et de roches acides dont la répartition spatiale a permis de distinguer les massifs de type CA (roches acides au coeur du massif), les massifs de type CB (roches basiques au coer du massif) et les massifs de type CR (récurrences de lentilles de roches basiques dans un massif zoné de type CA ou CB), mis en place dans le Paléozoïque supérieur généralement loin des grands ensembles métamorphiques. Tous ces massifs se sont mis en place diapiriquement au cours du métamorphisme régional et de la déformation hercynienne majeure.

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One of the main characteristics of the Hercynian geodynamic evolution of the Pyrenees is an intense magmatic activity producing large plutonic bodies. They have different sizes, various compositions and distinct emplacement levels. From these characteristics, a typology for these massifs is defined. Two main types of massifs have been recognized: 1) massifs with an homogenous composition founded in large regional metamorphic areas, and 2) massifs with an heterogenous composition of acid and basic rocks, whose spatial disposition permits the recognition of three sub-types: a) the CA type where acid rocks are at the core of the massif; b) the CB type where basic rocks are at the core of the massif, and c) the CR type where numerous basic xenoliths are scattered within either a CA or a CB type massif. These heterogenous massifs generally occur within Upper Paleozoic rocks and usually far away from regional metamorphic areas. All of these massifs were emplaced diapirically during the regional metamorphism and the main Hercynian deformation.

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Zusammenfassung Ein wichtiges charakteristisches Merkmal der geodynamischen Entwicklung der Pyrenäen während der herzynischen Phase ist eine hohe magmatische Aktivität, auf die Plutone größerer Ausdehnung zurückgeführt werden. Größe, Mineralogie und Erstarrungstiefe der Plutone variieren. Anhand dieser Charakteristika können die Intrusivkörper in zwei Hauptgruppen differenziert werden. Die erste Gruppe (1) sind Plutone homogener Zusammensetzung in regionalmetamorph überprägten Gebieten. Die zweite sind heterogen zusammengesetzte Plutone (2) saurer und basischer Magmatite, deren räumliche Anordnung eine Untergliederung in drei Untergruppen ermöglicht:a) Bei dem CA-Typ befinden sich saure Gesteine im Kern; bei b), dem CB-Typ, liegen basische Gesteine im Kern vor und bei c), einem CR genannten Typ, sind zahlreiche basische Xenolithe entweder in dem CA-oder dem CB-Typ verstreut vorhanden. Diese heterogenen Plutone findet man allein in spätpaläozoischen Gesteinen und in der Regel weit entfernt von Gebieten, die metamorph beeinflußt wurden. Sämtliche Plutone haben eine Diapir-ähnliche Form und intrudierten zeitgleich mit der Regionalmetamorphose und der Hauptphase der herzynischen Deformation.

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A Conceptual Model of Field Behavior of Air Sparging and Its Implications for Application

The basic physics of air flow through saturated porous media are reviewed and implications arc drawn for the practical application of air sparging. A conceptual model of the detailed behavior of an air sparging system is constructed using elements of multiphase flow theory and the results of recent experimental work. Implications of the conceptual model on air sparging topics are discussed. The meaning of radius of influence in the context of air sparging is found to be ambiguous. The hydrodynamic effects of air sparging such as mounding of ground water and flow impedance are explored. Limitations on rates of remediation and operational strategics for improving sparging effectiveness are examined.     

Monitoring Soil Water Content by Vertical Temperature Variations

The availability of high sensitivity temperature sensors (0.001 K sensitivity platinum resistors), which can be positioned at intervals of a few centimeters along a vertical profile in the unsaturated zone, allows short‐term in situ determinations—one day or even less—of the thermal diffusivity. The development of high data storage capabilities also makes this possible over long periods and the relative variations in thermal diffusivity allow the monitoring of the variations in water content. The processing of temperature measurements recorded at different depths is achieved by solving the heat equation, using the finite elements method, with both conductive and convective heat transfers. A first set of measurements has allowed this approach to be validated. Water content variations derived from thermal diffusivity values are in excellent agreement with TDR measurements carried out on the experimental site at Boissy‐le‐Châtel (Seine et Marne, France).