Cartographie de l’érosion dans le bassin versant de l’Oued Mina en Algérie par télédétection et SIG

Résumé

Dans cette étude, on a fait appel à la télédétection et aux systèmes d’information géographiques (SIG) pour évaluer et cartographier l’érosion hydrique en utilisant l’équation universelle des pertes en sol USLE dans le bassin versant de l’Oued Mina en Algérie. Ce bassin est caractérisé par une grande irrégularité dans les précipitations, une forte pente, une lithologie essentiellement marneuse et une couverture végétale très faible ce qui le rend très vulnérable à l’érosion. L’USLE est la combinaison de six facteurs spécifiques qui décrivent les caractéristiques du bassin versant. Les données de télédétection multi-temporelles et les SIG sont utilisés pour évaluer et cartographier chaque facteur individuellement. L’intégration des cartes thématiques des facteurs du modèle USLE dans le SIG permet de cerner l’impact de chaque facteur dans les pertes en sol, de classer par importance relative les zones d’érosion, et de quantifier les pertes en sol dans le bassin.

Editeur Z.W. Kundzewicz

Citation Toumi, S., Meddi, M., Mahé, G., et Brou, Y.T., 2013. Cartographie de l’érosion dans le bassin versant de l’Oued Mina en Algérie par télédétection et SIG. Hydrological Sciences Journal 58 (7), 1542–1558.     

Spatial spring distribution of the copepod Eurytemora affinis (Copepoda,Calanoida) in a restoring estuary,the Scheldt (Belgium)

The spatial spring distribution of Eurytemora affinis (adults and C5) in the Scheldt estuary (Belgium) brackish and freshwater reaches was studied in between 1996 and 2007. The bulk of the E. affinis population being generally situated in the brackish water reach (salinity > 0.5); we studied which environmental factors are responsible for its recent sporadic occurrence in the freshwater estuarine reach. Using PLS analysis, it is shown that its presence upstream is limited by a sufficient oxygen concentration (>4 mg l⁻¹) that is associated with temperature. Not only are the environmental conditions in the upstream zone important, but also the frequent presence of an O₂ minimum zone in the mid-estuary (O₂ min < 1.3 mg l⁻¹) seems to block the movement of the downstream E. affinis population in an upstream direction. Occasionally, the bulk of the population is however situated upstream. During these periods, high E. affinis abundance was also observed in the Durme tributary. Our findings suggest the possibility to use E. affinis as an “indicator” species of water quality, but also lead us to stress the necessity to consider conditions over the entire estuary when studying restoration effects, not exclusively in the zone of interest.     

A Late Cretaceous theropod caudal vertebra from the Sultanate of Oman

A caudal vertebra collected from conglomerates of the Al-Khod Formation (Late Cretaceous) in the Al-Khod area, Sultanate of Oman, is assigned to a medium-sized theropod dinosaur. The Al-Khod discovery represents one of the very few dinosaur records from the Middle East.     

Financing LNG carriers

The author examines the various methods of finance for LNG carriers at each stage of funding. First, he describes the various factors involved in the funding of LNG carriers, and continues by highlighting the different methods of finance. He concludes by summarizing the prospects for shipping finance in a severely depressed ship sale and purchase market.     

Laboratory observations of electron temperature in the wake of a sphere in a streaming plasma

A parametric study was performed of electron temperature variation in the wake of a conducting sphere in a streaming plasma. The flow conditions were varied as follows: the ambient electron temperatures in the range 850–2450 K; the ambient electron densities in the range 5 × 10⁴?7 × 10⁵/cm³; and body potentials relative to plasma potential in the range of + 1.7 to ?2.8 V for an ion beam energy of ～4 eV. Electron temperature enhancements were observed which ranged up to 200 per cent above ambient in the nearest proximity of the body surface. The magnitude of the enhancement depends upon the ambient density, temperature and body potential.     

Stability of elastic frames subjected to earthquake excitations

Dynamic stability of elastic multistorey frame structures subjected to vertical earthquake ground accelerations is studied. Different stationary, non-stationary, white and non-white random models for earthquake strong motion are considered. The concepts of mean-square and almost-sure stability are reviewed and the corresponding stability theorems are presented. Several general criteria regarding the dynamic stability of the equilibrium state of multistorey frames subjected to random excitations are developed. A few examples concerning the stability of single and multi-degree-of-freedom structures under earthquake excitations are presented. The stability of motion of frames under combined horizontal–vertical acceleration is also briefly discussed.     

Relativistic disturbances in a finite elastic rod in an electromagnetic field

Summary The paper is concerned with the investigation of the disturbances of a finite elastic rod within the framework of relativistic mechanics of continua and of relativistic electrodynamics under specified boundary conditions.     

Beach erosion along the coastline of Alexandria, Egypt

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Comparison of Kansas Data with High-resolution Large-eddy Simulation Fields

The surface layer of an atmospheric boundary layer (ABL) is most accessible to field measurements and hence its ensemble-mean structure has been well established. The Kansas field measurements were the first detailed study of this layer, providing numerous benchmark statistical profiles for a wide range of stability states. Large-eddy simulation (LES), in contrast, is most suitable for studying the mixed layer of the ABL where the energy-containing range of the vertical velocity field is well resolved. In the surface layer, typical large-eddy simulations barely resolve the energy-containing vertical-velocity fields and hence do not provide sufficient data for a detailed analysis.We carried out a nested-mesh simulation of a moderately convective ABL (-z_i/L = 8) in which the lower 6% of the boundary layer had an effective grid resolution of 512³. We analyze the LES fields above the 6th vertical grid level (z = 23 m) where the vertical velocity field has a well formed inertial subrange, for a detailed comparison with the Kansas results. Various terms in the budgets of turbulent kinetic energy, temperature variance, Reynolds stress, temperature flux, and some higher order moments are compared. The agreement is generally quite good; however, we do observe certain discrepancies, particularly in the terms involving pressure fluctuations.