Dr. NEHAL Laounia نحال لعونية
Faculté des Sciences et de la Technologie
Département Hydraulique
Grade : Maitre de conférence classe B
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Ouvrages Publications Projets Communications


Parcours académique :

Ingénieur d’état en Hydraulique urbaine "Ouvrages hydrotechniques", Juin 2001, thème de recherche : "Apport des SIG dans l’étude des potentialités en eau des monts de Tlemcen", Université Mustapha Stambouli de Mascara. Magistère en "Hydraulique et dynamique des rivières", Mars 2005, Thème de recherche: “Study of the flow through Non-submerged vegetation”, Hohai University, Nanjing, Chine. Doctorat en Sciences de la terre et de l'univers spécialité "hydrogéologie", Décembre 2018, Thème de recherche: "Suivi spatio-temporel de l’évapotranspiration d’un couvert végétal par utilisation des données satellitaires à haute et à faible résolutions : Cas d’une région choisie dans la plaine de la Macta (Ouest Algérien)", Université Mustapha Stambouli de Mascara.


  • Contribution to the study of the flow resistance in a flume with artificial emergent vegetation
  • La revue : Larhyss journal
    Domaine :
    Mots Clés : emergent vegetation, density, Manning resistance coefficient, Drag
    Auteur : Hamimed, A., Nehal, L., Benslimane, M., Khaldi, A
    Issn : 1112-3680 Eissn : vol : , Num : 15, pp : 55-63
  • Date de publication : 2013-09-15
  • Résume :
    Vegetation growing in the water along rivers has been the subject of several studies since it was recognized that it could have a significant impact on the water flow. It may increases resistance to flow and causes higher water levels. Also, it has affects on the turbulent structure such as the mean velocity profiles. For flow of water through emergent vegetation, previous investigations show different results. Hence, better knowledge on its impact on flow conditions is needed. The purpose of this paper is to investigate, how density and placement of emergent vegetation influence flow resistance, water depth and velocity profile. Experiments using artificial vegetation selected to simulate emergent vegetation were carried out in a laboratory flume instead of natural channel, and Manning’s n is used to denote the resistance coefficient. The results show large variations in the Manning resistance coefficient with depth of flow and vegetative density. Vegetation causes resistance to flow; it reduces flow velocities and increases water depth. For the vegetation densities considered, the presence of foliage significantly reduces the mean velocities. Also mean velocity profile is set by the vertical structure of the vegetative drag.

  • Using the Priestley-taylor expression for estimating actual evapotranspiration and monitoring water stress from satellite Landsat ETM + data". Larhyss journal
  • La revue : Larhyss journal
    Domaine :
    Mots Clés : Remote sensing, triangle concept, energy balance, evapotranspiration, vegetation index, surface temperature, Priestley-Taylor
    Auteur : Hamimed, A., Benslimane, M., Khaldi, A., Nehal, L., Zaagane, M
    Issn : Eissn : vol : , Num : 18, pp : 179-195
  • Date de publication : 2014-09-16
  • Résume :
    The quantification of evapotranspiration from irrigated areas is important for agriculture water management, especially in arid and semi-arid regions where water deficiency is becoming a major constraint in economic welfare and sustainable development. Conventional methods that use point measurements to estimate evapotranspiration are representative only of local areas and cannot be extended to large areas because of landscape heterogeneity. Remote sensing-based energy balance models are presently most suited for estimating evapotranspiration at both field and regional scales. In this study, we aim to develop a methodology based on the triangle concept, allowing estimation of evapotranspiration through the classical equation of Priestley and Taylor (1972) where the proportional coefficient α in this equation is ranged using a linear interpolation between surface temperature and Normalized Difference Vegetation Index (NDVI) values. Preliminary results using remotely sensed data sets from Landsat ETM+ over the Habra Plains in west Algeria are in good agreement with ground measurements. The proposed approach appears to be more reliable and easily applicable for operational estimation of evapotranspiration over large areas.

  • Mapping and monitoring soil erosion in a watershed in western Algeria. Arabian Journal of Geosciences
  • La revue : Arabian Journal of Geosciences
    Domaine :
    Mots Clés : Erosion . GIS . Remote sensing . USLE . Fergougwatershed . North-Western Algeria
    Auteur : Djazia Bouderbala, Zahira Souidi, Frédéric Donze, Mohamed Chikhaoui, Laounia Nehal
    Issn : Eissn : vol : 11, Num : 23, pp : 744
  • Date de publication : 2018-11-16
  • Résume :
    Fergoug watershed is subject to severe water erosion and land degradation that threaten agricultural sustainability for local populations. Soil loss and degradation by water erosion were estimated using the universal soil loss equation (USLE). The spatial distribution of soil losses was determined using the following parameters: the erosivity factor (R), obtained using climatic data from 12 local stations over a period of 41 years; the land cover factor (C), obtained using LandSat-TM satellite imagery 7 and 8; the erodibility factor (K), estimated from soil particle size analyses; and the topographic factor (LS), obtained from a digital terrain model. The Fergoug watershed is characterized by complex topography, and the topographic factor reached a value of 14.29. The erodibility factor K ranged from 0.08 to 0.38, and high values were recorded for about 20% of the watershed. The rainfall erosivity factor R ranged between 212.32 and 146.73 from east to west. The plant cover factor varied inter- and intraannually from 2.24 in May 2000 to 0.06 in May 2015. As a result, soil losses varied from 0.35 to 617.66 tons per hectare per year (t/ha/year) in a rainy year, and from 0.27 to 1188.92 t/ha/year in a dry year. The combined effects of the slope angle and the vegetation cover were shown to play a major role in soil losses in this area.

  • La revue : Mining Science
    Domaine : Télédétection
    Mots Clés : drought, Northwestern Algeria, SPI, NDVI, linear regression, satellite imagery
    Auteur : Malika ABBES, Abderrahmane HAMIMED, Aicha LAFRID, Habib MAHI, Laounia NEHAL
    Issn : 0370-0798 Eissn : vol : 25, Num : , pp : 85–113
  • Date de publication : 2018-08-02
  • Résume :
    Over the last decades, Algeria has witnessed intense and persistent drought periods characterized by a significant rainfall deficit. The Northwestern Algeria, such as the most south Mediterranean regions, is marked by alternating wet and dry periods and mixing between Atlantic and Mediterranean airs. In a climate context increasingly disturbed by anthropogenic activities, it is essential to analyze the dry episodes at spatial and temporal scales. In order to understand this problem, this work aims to use the potential of Landsat satellite imagery for monitoring drought conditions in the Cheliff watershed in the northwestern Algeria. As known, the behavior of vegetation is strongly related to climate changes. On this basis, a comparison of the variations in the standardized normalized difference vegetation index (NDVI) and those of the drought indices calculated from meteorological data was implemented. In fact, the rainfall series from fifty meteorological stations were analyzed. The standardized precipitation index (SPI) was calculated for the years 1987, 2000, 2006, 2011 and 2015, corresponding to the acquisition dates of Landsat images. Similarly, an extraction of the NDVI values was performed for each meteorological station. The linear regression between SPI and NDVI showed a good correlation. Thus, the obtained results enabled establishing a new drought index based essentially on satellite data. This index represents the advantage for monitoring spatially the drought phenomena and can solve the problem of climatic data lack.

  • Study of the flow through non-submerged vegetation
  • La revue : Journal of Hydrodynamics
    Domaine : Open channel flow
    Mots Clés : open channel flow , nonsubmerged vegetation , vegetation density , flow resistance , velocity distribution
    Auteur : NEHAL Laounia , YAN Zhong min , XIA Ji hong
    Issn : 1001-6058 Eissn : vol : 17, Num : 4, pp : 498-502
  • Date de publication : 2005-08-11
  • Résume :
    Vegetation is an important feature of many rivers. Vegetation along rivers produces high resistance to flow and, as a result, has a large impact on water levels in rivers and lakes. The effects of instream-unsubmerged vegetation (such as the reed-similar Kalmus) on flow resistance and velocity distributions is studied in the paper. Artificial vegetation is used in the experimental study to simulate the Acorus Calmus L. As shown in experimental tests the resistance depends strongly on vegetation density and the Manning resistance coefficient varies with the depth of flow. A simplified model based on concepts of drag is developed to evaluate the roughness coefficient (Manning's n) for nonsubmerged vegetation. In vegetated channels the overall flow resistance is influenced significantly by the distribution pattern of the vegetated beds. Within vegetation, vertical variation in velocity is different from that in the nonvegetated bed, which reflects the variation in vegetation density. Vertical turbulent transport of momentum is negligible as demonstrated by experiments.

  • Sinuosity-Driven Water Pressure Distribution on Slope of Slightly-Curved Riparian Zone: Analytical Solution Based on Small-disturbance Theory and Comparison to Experiments
  • La revue : Water
    Domaine :
    Mots Clés : riparian zone; slightly-curved; water pressure distribution; small-disturbance theory
    Auteur : Jihong Xia, Genting Yu, Junqiang Lin, Weijie Cao, Zihan Yi, Lihuai Lin, Laounia Nehal
    Issn : Eissn : vol : 8, Num : 2, pp : 61
  • Date de publication : 2016-02-17
  • Résume :
    A curved riparian zone can create highly complex flow patterns that have a great effect on erosion, pollutant transport, surface water-groundwater exchange and habitat qualities. The small-disturbance theory has been applied to derive the analytical solutions of pressure distributions along a sinusoidal riverbank. Experiments have also been performed to test the hydrodynamic and geomorphic effects on pressure distribution and to verify the applicability of the derived expressions. The derived expressions were simple, accurate and agreed remarkably well with experimental results for the riparian banks with a low degree of curvature. On the contrary, when a riparian bank had a high degree of curvature, these expressions applying the approach of small-disturbance, could not effectively estimate the pressure distributions for a complex bank boundary or complex flow conditions. Moreover, sensitive analysis has indicated that the disturbed pressures along the riparian banks increased with increasing Froude number Fr, as well as the ratio of bank amplitude to wavelength a/. However, a/ has been found to have more significant influence on pressure variation in subcritical flow.

  • Development of a GIS-Based Decision Support System for Diagnosis of River System Health and Restoration
  • La revue : Water
    Domaine : GIS
    Mots Clés : decision support system (DSS); diagnosis; geographic information systems (GIS); river health
    Auteur : Jihong Xia, Lihuai Lin, Junqiang Lin, Laounia Nehal
    Issn : 2073-4441 Eissn : vol : 6, Num : , pp : 3136-3151
  • Date de publication : 2014-10-17
  • Résume :
    The development of a decision support system (DSS) to inform policy making has been progressing rapidly. This paper presents a generic framework and the development steps of a decision tool prototype of geographic information systems (GIS)-based decision support system of river health diagnosis (RHD-DSS). This system integrates data, calculation models, and human knowledge of river health status assessment, causal factors diagnosis, and restoration decision making to assist decision makers during river restoration and management in Zhejiang Province, China. Our RHD-DSS is composed of four main elements: the graphical user interface (GUI), the database, the model base, and the knowledge base. It has five functional components: the input module, the database management, the diagnostic indicators management, the assessment and diagnosis, and the visual result module. The system design is illustrated with particular emphasis on the development of the database, model schemas, diagnosis and analytical processing techniques, and map management design. Finally, the application of the prototype RHD-DSS is presented and implemented for Xinjiangtang River ofHaining County in Zhejiang Province, China. This case study is used to demonstrate the advantages gained by the application of this system. We conclude that there is great potential for using the RHD-DSS to systematically manage river basins in order to effectively mitigate environmental issues. The proposed approach will provide river managers and designers with improved insight into river degradation conditions, thereby strengthening the assessment process and the administration of human activities in river management.

  • Hydraulic features of flow through emergent bending aquatic vegetation in the riparian zone.
  • La revue : Water
    Domaine : Hydrodynamique
    Mots Clés : riparian zone; flexible aquatic vegetation; ecohydraulics; Manning coefficient n; vertical velocity; turbulence
    Auteur : Jihong Xia, Launia Nehal
    Issn : 2073-4441 Eissn : vol : 5, Num : 4, pp : 2080-2093
  • Date de publication : 2013-12-13
  • Résume :
    Vegetation in riparian zones has a significant influence on resistance, velocity distribution and turbulence intensity. This study experimentally investigated the effect of emergent bending riparian zone vegetation on the flow. The results showed that the frond and stem parts of Acorus calami had different influences on hydraulic features and that the relative depth ratio of water depth h to stem height hs was a key determinant of those influences. Manning coefficient n varied greatly with the variation of vegetation densities, relative depth ratio of water depth h to stem height hs, Re and Fr. Manning coefficient n increased with increasing vegetation density, particularly in cases when h/hs > 1. The velocity distributions did not follow logarithmic profiles, but they instead exhibited double logarithmic profiles. In addition, vegetation characteristics were shown to influence the height of maximum velocity. The position of maximum velocity is further away from the bed in cases with denser vegetation distribution. Finally, turbulence intensity showed more significant variation in the stem part and peaked near the middle of the stem, at z/hs = 0.5, where z was the distance from the bottom.

  • Evapotranspiration and Surface Energy Fluxes Estimation Using the Landsat-7 Enhanced Thematic Mapper Plus Image over a Semiarid Agrosystem in the North-West of Algeria
  • La revue : Revista Brasileira de Meteorologia
    Domaine : Télédétection
    Mots Clés : evapotranspiration, remote sensing, METRIC, energy balance, Landsat
    Auteur : Nehal Laounia, Hamimed Abderrahmane, Khaldi Abdelkader, Souidi Zahira, Zaagane Mansour
    Issn : 0102-7786 Eissn : 1982-4351 vol : 32, Num : 4, pp : 691-702
  • Date de publication : 2017-07-05
  • Résume :
    Monitoring evapotranspiration and surface energy fluxes over a range of spatial and temporal scales is crucial for many agroenvironmental applications. Different remote sensing based energy balance models have been developed, to estimate evapotranspiration at both field and regional scales. In this contribution, METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration), has been applied for the estimation of actual evapotranspiration in the Ghriss plain in Mascara (western Algeria), a semiarid region with heterogeneous surface conditions. Four images acquired during 2001 and 2002 by the Landsat-7 satellite were used. The METRIC model followed an energy balance approach, where evapotranspiration is estimated as the residual term when net radiation, sensible and soil heat fluxes are known. Different moisture indicators derived from the evapotranspiration were then calculated: reference evapotranspiration fraction, Priestley-Taylor parameter and surface resistance to evaporation. The evaluation of evapotranspiration and surface energy fluxes are accurate enough for the spatial variations of evapotranspiration rather satisfactory than sophisticated models without having to introduce an important number of parameters in input with difficult accessibility in routine. In conclusion, the results suggest that METRIC can be considered as an operational approach to predict actual evapotranspiration from agricultural areas having limited amount of ground information.

  • "Contribution à la spatialisation de l'évapotranspiration d'un agro-système semi-aride en Algérie par utilisation de la télédétection et du modèle METRIC".
  • La revue : Physio-Géo - Géographie Physique et Environnement
    Domaine :
    Mots Clés : évapotranspiration, bilan d'énergie, télédétection, Lansdat, METRIC, Algérie
    Auteur : Hamimed, A., Nehal, L., Khaldi, A., & Azzaz, H
    Issn : Eissn : vol : 8, Num : , pp : 197-213
  • Date de publication : 2014-07-23
  • Résume :
    L'évapotranspiration est une composante majeure du bilan hydrologique, car elle exprime les échanges de masse et d'énergie entre le système sol-eau-végétation et l'atmosphère. Sa connaissance précise est indispensable dans plusieurs applications environnementales, telles que la climatologie, l'hydrologie et l'agronomie. La télédétection est un outil incontournable pour l'évaluation de l'évapotranspiration, à la fois dans l'espace et dans le temps. Dans cette contribution, le modèle de spatialisation METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) est appliqué pour l'estimation de l'évapotranspiration d'un agro-système semi-aride situé dans la plaine du Sersou en Algérie. Deux images du satellite Landsat 7 acquises le 13 mars 2012 et le 30 avril 2012 ont été utilisées. Le modèle METRIC se base sur la résolution de l'équation du bilan d'énergie à la surface, où l'évapotranspiration est estimée comme le terme résiduel lorsque le rayonnement net, le flux de chaleur sensible et le flux de chaleur du sol sont connus. Différents indices d'alimentation en eau de surface dérivés de l'évapotranspiration ont été ensuite calculés : la fraction d'évapotranspiration de référence, le paramètre de PRIESTLEY-TAYLOR et la résistance de surface à l'évaporation. Ces indices permettent le diagnostic quantitatif de l'état hydrique du pixel. Les résultats obtenus concernent la validation du modèle utilisé pour l'analyse de la distribution spatiale de l'évapotranspiration et des flux énergétiques de surface. En conclusion, les résultats montrent que le modèle peut être considéré comme une approche prometteuse de spatialisation de l'évapotranspiration dans le cas des régions où les informations de terrain sont rares ou difficiles à collecter.

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