Showing papers in "Arabian Journal of Geosciences in 2013"

Landslide susceptibility mapping at Vaz Watershed (Iran) using an artificial neural network model: a comparison between multilayer perceptron (MLP) and radial basic function (RBF) algorithms

Abstract: Landslide susceptibility and hazard assessments are the most important steps in landslide risk mapping. The main objective of this study was to investigate and compare the results of two artificial neural network (ANN) algorithms, i.e., multilayer perceptron (MLP) and radial basic function (RBF) for spatial prediction of landslide susceptibility in Vaz Watershed, Iran. At first, landslide locations were identified by aerial photographs and field surveys, and a total of 136 landside locations were constructed from various sources. Then the landslide inventory map was randomly split into a training dataset 70 % (95 landslide locations) for training the ANN model and the remaining 30 % (41 landslides locations) was used for validation purpose. Nine landslide conditioning factors such as slope, slope aspect, altitude, land use, lithology, distance from rivers, distance from roads, distance from faults, and rainfall were constructed in geographical information system. In this study, both MLP and RBF algorithms were used in artificial neural network model. The results showed that MLP with Broyden–Fletcher–Goldfarb–Shanno learning algorithm is more efficient than RBF in landslide susceptibility mapping for the study area. Finally the landslide susceptibility maps were validated using the validation data (i.e., 30 % landslide location data that was not used during the model construction) using area under the curve (AUC) method. The success rate curve showed that the area under the curve for RBF and MLP was 0.9085 (90.85 %) and 0.9193 (91.93 %) accuracy, respectively. Similarly, the validation result showed that the area under the curve for MLP and RBF models were 0.881 (88.1 %) and 0.8724 (87.24 %), respectively. The results of this study showed that landslide susceptibility mapping in the Vaz Watershed of Iran using the ANN approach is viable and can be used for land use planning.

Application of weights-of-evidence and certainty factor models and their comparison in landslide susceptibility mapping at Haraz watershed, Iran

Abstract: The main goal of this study was to investigate the application of the weights-of-evidence and certainty factor approaches for producing landslide susceptibility maps of a landslide-prone area (Haraz) in Iran For this purpose, the input layers of the landslide conditioning factors were prepared in the first stage The landslide conditioning factors considered for the study area were slope gradient, slope aspect, altitude, lithology, land use, distance from streams, distance from roads, distance from faults, topographic wetness index, stream power index, stream transport index and plan curvature For validation of the produced landslide susceptibility maps, the results of the analyses were compared with the field-verified landslide locations Additionally, the receiver operating characteristic curves for all the landslide susceptibility models were constructed and the areas under the curves were calculated The landslide locations were used to validate results of the landslide susceptibility maps The verification results showed that the weights-of-evidence model (7987%) performed better than certainty factor (7202%) model with a standard error of 00663 and 00756, respectively According to the results of the area under curve evaluation, the map produced by weights-of-evidence exhibits satisfactory properties

A knowledge-driven GIS modeling technique for groundwater potential mapping at the Upper Langat Basin, Malaysia

Abstract: The aim of this paper is to use a knowledge-driven expert-based geographical information system (GIS) model coupling with remote-sensing-derived parameters for groundwater potential mapping in an area of the Upper Langat Basin, Malaysia. In this study, nine groundwater storage controlling parameters that affect groundwater occurrences are derived from remotely sensed imagery, available maps, and associated databases. Those parameters are: lithology, slope, lineament, land use, soil, rainfall, drainage density, elevation, and geomorphology. Then the parameter layers were integrated and modeled using a knowledge-driven GIS of weighted linear combination. The weightage and score for each parameter and their classes are based on the Malaysian groundwater expert opinion survey. The predicted groundwater potential map was classified into four distinct zones based on the classification scheme designed by Department of Minerals and Geoscience Malaysia (JMG). The results showed that about 17% of the study area falls under low-potential zone, with 66% on moderate-potential zone, 15% with high-potential zone, and only 0.45% falls under very-high-potential zone. The results obtained in this study were validated with the groundwater borehole wells data compiled by the JMG and showed 76% of prediction accuracy. In addition statistical analysis indicated that hard rock dominant of the study area is controlled by secondary porosity such as distance from lineament and density of lineament. There are high correlations between area percentage of predicted groundwater potential zones and groundwater well yield. Results obtained from this study can be useful for future planning of groundwater exploration, planning and development by related agencies in Malaysia which provide a rapid method and reduce cost as well as less time consuming. The results may be also transferable to other areas of similar hydrological characteristics.

Groundwater quality assessment using WQI and GIS techniques, Dindigul district, Tamil Nadu, India

Abstract: The quality of groundwater was assessed by determining the physicochemical parameters (pH, EC, TDS and TH) and major ions concentration (HCO3, Cl, FSO4, Ca, Mg, Na and K) around Dindigul district, Tamil Nadu, India. The groundwater samples were collected from 59 bore wells covering the entire study area and analyzed using standard methods. The GIS mapping technique were adopted to highlight the spatial distribution pattern of physicochemical parameters and major ion concentration in the groundwater. Gibbs diagram reveals that the source of major ions is predominantly derived from rock–water interaction and evaporation dominance process. The salt combinations of the aquifers are dominated by CaHCO3, mixed CaMgCl, mixed CaMgHCO3 and CaCl facies type due to leaching and dissolution process of weathered rocks. The Canadian Council of Ministers of Environment Water Quality Index (CCMEWQI) suggests that most of the groundwater quality falls under good to marginal category. The statistical analysis indicates that the presence of major ions and physicochemical parameters are chiefly controlled by rock–water interaction and residence time of the groundwater. However, the major nutrient like nitrite in the groundwater probably comes from anthropogenic process. Based on the groundwater quality standards, majority of the samples are suitable for drinking purposes except few in the study area.

Shoreline change analysis along the coast between Kanyakumari and Tuticorin of India using remote sensing and GIS

Abstract: Shoreline is one of the rapidly changing landform in coastal area. So, accurate detection and frequent monitoring of shorelines are very essential to understand the coastal processes and dynamics of various coastal features. The present study is to investigate the shoreline changes along the coast between Kanyakumari and Tuticorin of south India, where hydrodynamic and morphologic changes occur continuously after the December 2004 tsunami. Multi-date satellite data of Indian Remote Sensing (IRS) satellites (1999, 2000, 2003, 2005, and 2006) are used to extract the shorelines. The satellite data is processed by using the ERDAS IMAGINE 9.1 software and analyzed by ArcGIS 9.2 workstation. The different shoreline change maps are developed and the changes are analyzed with the shoreline obtained from the Survey of India Toposheets (1969). The present study indicates that accretion was predominant along the study area during the period 1969–1999. But recently (from 1999 onwards), most of the coastal areas have experienced erosion. The study also indicates the reversal of shoreline modifications in some coastal zones. The coastal areas along the headlands have experienced both erosion and accretion. Though the coastal erosion is due to both natural and anthropogenic activities, the coastal zones where sand is mined have more impacts and relatively more rate of erosion than that of other zones. Improper and in-sustainable sand mining leads to severe erosion problem along this area. So the concept of sustainable management should be interpreted in the management of the near-shore coastal sand mining industry.

Application of concentration–number (C–N) multifractal modeling for geochemical anomaly separation in Haftcheshmeh porphyry system, NW Iran

Abstract: Geochemical anomaly separation using the concentration–number (C–N) method at the Haftcheshmeh porphyry system in NW Iran is the aim of this study. We used lithogeochemical data sets to explore Cu, Mo, Au and Re mineralization in gabbroic, dioritic and monzonitic units at the Haftcheshmeh Cu–Mo porphyry system. The obtained results were interpreted using a rather extensive set of information available for each mineralized area, consisting of detailed geological mapping, structural interpretation and alteration data. Threshold values of elemental anomalies for the mineralized zone were computed and compared with the statistical methods based on the data obtained from chemical analyses of samples for the lithological units. Several anomalies at local scale were identified for Cu (40 ppm), Mo (12 ppm), Au (79 ppb), and Re (0.02 ppm), and the results suggest the existence of local Cu anomalies whose magnitude generally is above 500 ppm. The log–log plots show the existence of three stages of Cu and Mo enrichment, and two enrichment stages for Au and Re. The third and most important mineralization event is responsible for presence of Cu at grades above 159 ppm. The identified anomalies in Haftcheshmeh porphyry system, and distribution of the rock types, are mainly gabbrodiorite–monzodiorite, granodiorite and monzodiorite–diorite that have special correlation with Cu–Mo and gabbroic and monzonitic rocks, especially the gabbrodiorite–monzodiorite type, which is of considerable importance. The study shows that these elemental anomalous parts have been concentrated dominantly by potassic and phyllic, argillic and propylitic alterations within the gabbroic, monzonitic and dioritic rocks especially in the gabrodioritic type in certain parts of the area. The results, which were compared with fault distribution patterns, revealed a positive correlation between mineralization in anomalous areas and the faults present in the mineralized system.

GIS-based analytic hierarchy process as a multicriteria decision analysis instrument: a review

Abstract: Information and communication technology, which has been incorporated and provided in the Geographic Information System (GIS), is valuable and effective geospatial information for the decision makers in improving their decisions in planning and development. The integration of this GIS using the multicriteria decision analysis approach provides an environment to the decision makers in citing areas using land suitability analysis procedures. This review paper particularly examines the GIS-based analytic hierarchy process as a multicriteria analysis/evaluation technique in land suitability analysis by means of literature reviews and surveys.

Effect of temperature, pressure, salinity, and surfactant concentration on IFT for surfactant flooding optimization

Abstract: In this research, effect of temperature, pressure, salinity, surfactant concentration, and surfactant type on interfacial tension (IFT) and critical micelle concentration of Saudi Arabian crude oil and various aqueous phases were investigated. The temperature ranged from ambient condition to 90°C, and the pressures were varied from atmospheric to 4,000 psi (27.58 MPa). Surfactant solutions were prepared using several aqueous phases, i.e., purified water, 10% brine consisting of 100% NaCl, 10% brine consisting of 95% NaCl and 5% CaCl2, and 10% brine consisting of 83% NaCl and 17% CaCl2. Out of 13 commercial surfactants, only three surfactants showed good solubility in pure water and brine. Those are Zonyl FSE Fluorosurfactant®, Triton X-100®, and Triton X-405®. Therefore, they were investigated thoroughly by measuring their efficiency in reducing the crude oil-aqueous phase IFT. Based on this screening process, laboratory surfactant flooding experiments for crude oil recovery were conducted using Triton X-405 and Triton X-100. The chemical flood was made at both original oil in place and at residual oil in place subsequent to conventional water flooding. Based on the obtained results, both surfactants were efficient, and more oil was recovered than that obtained through water flooding. Comparing both surfactant solutions, it was observed that Triton X-405 was more efficient than Triton X-100 at the same surfactant concentration and reservoir conditions.

Estimation of uniaxial compressive strength based on P-wave and Schmidt hammer rebound using statistical method

Abstract: Preparing high-quality samples, which can fulfill testing standards, from weak and block-in-matrix conglomerate for laboratory tests, is a big challenge in engineering projects. Hence, using indirect methods seems to be indispensable for determination uniaxial compressive strength (UCS). The main objective of this study is to estimate the relation between sonic velocity (Vp), Schmidt hammer rebound number (SCH) and UCS. For this reason, some samples of weak conglomeratic rock were collected from two different sites of dam in Iran (Bakhtiari and Hezardareh Formations). In order to evaluate the correlation, the measured and predicted values utilizing simple and multivariate regression techniques were examined. To control the performance of the proposed equation, root mean square error (RMSE) and value accounts for (VAF%) were determined. The VAF% and RMSE indices were computed as 94.34 and 1.56 for the relation between Vp and UCS from simple regression model. These were 94.39 and 1.6 between SCH and UCS, while these were 97.24 and 1.34 for uniaxial compressive strengths obtained from multivariate regression model.

Landslide susceptibility mapping based on frequency ratio and logistic regression models

Abstract: The aim of this study is to apply and compare a probability model, frequency ratio and statistical model, and a logistic regression to Sajaroud area, Northern Iran using geographic information system. Landslide locations of the study area were detected from interpretation of aerial photographs and field surveys. Landslide-related factors such as elevation, slope gradient, slope aspect, slope curvature, rainfall, distance to fault, distance to drainage, distance to road, land use, and geology were calculated from the topographic and geology map and LANDSAT ETM satellite imagery. The spatial relationships between the landslide location and each landslide-related factor were analyzed and then landslide susceptibility maps were produced using the frequency ratio and forward stepwise logistic regression methods. Finally, the maps were tested and compared using known landslide locations, and success rates were calculated. Predicted accuracy values for frequency ratio (79.48%) and logistic regression models showed that the map obtained from frequency ratio model is more accurate than the logistic regression (77.4%) model. The models used in this study have shown a great deal of importance for watershed management and land use planning.

Mixed mode crack propagation in low brittle rock-like materials

Abstract: Mixed mode fracture is quite common in rock structures Numerous investigators have used the Brazilian disk specimens with a central crack for investigating modes I, II, and mixed fracture toughness in brittle materials In this study, analytical, experimental, and numerical investigations were planned and performed on Central Straight Through Crack Brazilian Disk (CSCBD) specimens Ranking of geometrical parameters effective on the value of stress intensity factors (SIFs) of CSCBD specimens were obtained using stochastic analysis Furthermore, experimental tests were undertaken in order to evaluate the crack propagation in rock-like material of low brittleness Finally, numerical modeling was performed to assess the effect of crack length on the failure mode of CSCBD specimens Analytical analyses revealed that the inclination angle of the crack with respect to the diametrical load has the most important impact on the SIFs among the geometrical parameters of CSCBD specimen Performed experimental and numerical analyses also confirmed the effect of inclination angle and crack length and their impact on the mode of failure of the tested specimen

Evaluation of spatial variations in groundwater quality by WQI and GIS technique: a case study of Virudunagar District, Tamil Nadu, India

Abstract: Groundwater plays a major life support to mankind. It is the major source to meet the domestic, irrigation and industrial water demands. The depletion of groundwater through excessive consumption and less recharge in the study area has detoriated the quality of groundwater. The present study has analyzed the pre- and post-monsoon physicochemical data of groundwater samples from 49 different bore wells in Virudunagar district. Spatial distribution maps were prepared for various physicochemical parameters using geographic information system. These maps are further classified according to highest desirable, maximum permissible and not permissible prescribed by the World Health Organization. Furthermore, a water quality index (WQI) map was also generated to understand the groundwater quality in the study area. It was observed that the groundwater in the area is hard and alkaline in nature and the WQI reveals that most part of the study area fall under fair water quality class. Also, the effect of recharge during monsoon period has diluted the geochemistry of the groundwater. The application of GIS and WQI in the study area is a promising tool to understand the spatial pattern of groundwater quality and its management.

Multi-temporal annual soil loss risk mapping employing Revised Universal Soil Loss Equation (RUSLE) model in Nun Nadi Watershed, Uttrakhand (India)

Abstract: The present comparative study is multi-temporal in nature. The Revised Universal Soil Loss Equation (RUSLE), remote sensing, and GIS were used to model the soil loss estimation for soil conservation and vegetation rehabilitation in Nun Nadi watershed for the years 2000 and 2009. The estimated mean soil loss for the year 2000 and 2009 is 3,283.11 and 1,419.39 Mg ha−1 year−1, respectively. The study finds that about 80 % area has low or least risk of erosion and about 7 % is exposed to high or very high risk which indicates the improvement in terms of soil loss if we compare the data of both the time periods. The findings show that the rainfall, LULC change, and elevation are the main responsible factors for the soil loss in Nun Nadi watershed. Conservation measures have been adopted; however, the problem still remains serious and demands urgent attention.

Major ion composition and seasonal variation in the Lesser Himalayan lake: case of Begnas Lake of the Pokhara Valley, Nepal

Abstract: The Begnas Lake in the Pokhara Valley is one of the threatened habitats in Nepal. The major ion chemistry explains the status of most of the inorganic nutrients and their possible sources. However, the earlier studies mostly cover limnological investigations, and phytoplankton and zooplankton diversity. Thus, the present study has been conducted to investigate the geochemical processes and to examine the seasonal variation of chemical composition within Begnas Lake. The results showed that SO 4 2- , PO 4 3- , and NO 3 - increased compared with the previous values. The domination of Ca2+, Mg2+, and HCO 3 - explains the influence of carbonate weathering on the major ion concentration. In general, pH and dissolved oxygen decreased with the depth of water-column, while electric conductivity, total dissolved solids, HCO 3 - , Cl-, H4SiO4, K+, Mg2+, Ca2+, Mn2+, and Fe increased. Among the cations, the predominance of Ca2+ and Mg2+ as characterized by high (>0.6) (Ca2+ + Mg2+)/(Tz+) and (>0.8) (Ca2+ + Mg2+)/(Na+ + K+) equivalent ratios, also suggests prevalence of carbonate weathering. The low value of (Na+ + K+)/Tz+ ratio shows deficiency of Na+ and K+, suggesting low contribution of cations via aluminosilicate weathering. The C-ratio suggests a proton source derived both from oxidation of sulfide and dissolution and dissociation of atmospheric CO2 during different seasons. Though the major hydro-chemical parameters are within permissible limit, the increase in trophic state of the lake suggests that inherent biogeochemical processes make the limiting nutrients available, rendering eutrophic effect. Therefore, further comprehensive studies incorporating sediment–water interaction ought to be carried out to explain the ongoing phenomena and curb the eutrophication process in the lake.

Studying the stress redistribution around the longwall mining panel using passive seismic velocity tomography and geostatistical estimation

Abstract: Generally, knowledge of stress redistribution around the longwall panel causes a better understanding of the mechanisms that lead to ground failure, especially to rockbursts. In this paper, passive seismic velocity tomography is used to demonstrate the state of stress around the longwall mining panel. The mining-induced microseismic events were recorded by mounting an array of receivers on the surface, above the active panel. To determine the location of seismic events and execute the process of tomography, double-difference method is employed as a local earthquake tomography. Since passive sources are used, the ray coverage is insufficient to achieve the quality images required. The wave velocity is assumed to be the regionalized variable and it is therefore estimated in a denser network, by using geostatistical estimation method. Subsequently, the three-dimensional images of wave velocity are created and are sliced into the coal seam. These images clearly illustrate the stressed zones that they are appropriately in compliance with the theoretical models. Such compliance is particularly apparent in the front abutment pressure and the side abutment pressure near the tailgate entry. Movements of the stressed zones along the advancing face are also evident. The research conclusion proves that the combined method, based on double-difference tomography and geostatistical estimation, can potentially be used to monitor stress changes around the longwall mining panel continuously. Such observation could lead to substantial improvement in both productivity and safety of mining operations.

Grain size analysis and characterization of sedimentary environment along Thiruchendur coast, Tamilnadu, India

Abstract: Thiruchendur coast of southern Tamilnadu, India has been studied for grain-size spectrum and textural parameters namely mean, sorting, skewness and kurtosis. The grain-size spectrum shows a marked variation in the berm, high tide line (HTL) and low tide line (LTL) stretches. Variation in energy condition is controlled by geomorphology of the sedimentary beach. Textural pattern shows complicated profile as a result of the fluctuation in the physicochemical conditions due to the sediments and the marine interactions. Abundance of the medium sand to fine sand shows the prevalence of comparatively moderate- to low-energy condition in the Thiruchendur area. Linear discriminate function of the samples indicates an aeolian, shallow marine deposition environment and less influence of fluvial (7 %) process. CM diagram (C = one percentile in microns M = medium in microns) of Thiruchendur coast sediments suggests that deposition takes place by (1) rolling, (2) bottom suspension, (3) graded suspension. This is also supported by the wave energy in different stretches in beach line and also tractive current figure implies the sediments disturbed by the tractive and turbidity currents. The heavy minerals are concentrated in the berm (average, 11.8 %) and high tide line (average, 11.2 %) because of high-energy condition and aeolian action. Quartz microtextures show the mechanical action due to high-energy condition in Manapad and Kuduthalai areas, the chemical action because of to low-energy condition along the Thiruchendur, Kallamozhi areas.

Evaluation and comparison of bivariate and multivariate statistical methods for landslide susceptibility mapping (case study: Zab basin)

Abstract: Landslides are among the great destructive factors which cause lots of fatalities and financial losses all over the world every year. Studying of the factors affecting occurrence of landslides in a region and zoning the resulting damages will certainly play a crucial role in mitigating such phenomena. In this research, through geological maps and field studies, we primarily prepared a map for landslide distributions in Zab basin—an area of 520 km2 in the southwest mountainsides of West Azerbaijan Province. By applying other source of information such as the existing thematic maps, we studied and defined the factors (slope, slope aspect, distance to road, distance to drainage network, distance to fault, land use and land cover, geological factors, horizontal gravity acceleration of earthquakes, and climatic condition of the studied area) that affect occurrence of the landslides. To get better precision and higher speed and facility in our analysis, all descriptive and spatial information were entered into geographic information system (GIS) system and Ilwis software. We also used Satellite images (Landsat ETM+ and SPOT 5), producing land cover and landslide-inventory maps, respectively. After preparation of the influential parameters on landslides, we drew the zoning maps of slide hazard via four different statistical methods and then evaluated and compared them. By analyzing the obtained index and by comparing landslide distribution map and zoning map of landslide susceptibility prepared by each of the methods in GIS environment, we found that bivariate method of information value analysis, bivariate method of density-area, multivariate method with linear regression analysis, and multivariate method of discriminate analysis take priority, respectively. Finally, as this research shows, despite their simplicity, bivariate statistical methods have more acceptable precision than multivariate methods, and consequently, they are more compatible with landslide susceptibility of the region. From the results, lithology, slope, annual rainfall, land cover, slope aspect, distance to waterway, distance to road, horizontal gravity acceleration, and distance to fault are very influential to landslides in the region.

Hydrochemistry of groundwater in a coastal region of Cuddalore district, Tamilnadu, India: implication for quality assessment

Abstract: A hydrogeochemical investigation was conducted in a coastal region of Cuddalore district to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. The geology of the study area comprises of sandstone, clay, alluvium, and laterite soils of Tertiary and Quaternary age. A total of 18 groundwater samples were analyzed for 14 different water quality parameters and the result indicates higher concentrations of ions like Cl (3,509 mg/l), Na (3,123 mg/l), and HCO3 (998 mg/l) when compared with WHO, BIS, and ISI standards. A positive correlation (r2 = 0.82) was observed between Na and Cl, indicating its sources from salt water intrusion. Three factors were extracted with a total variance of 64% which indicates the sources of salinization, cation exchange, and anthropogenic impact to the groundwater. The Piper trilinear diagram indicates both Na–Cl and mixed Na–HCO3–Cl-type, indicating that groundwater was strongly affected by anthropogenic activities. The plot of (Ca + Mg)/(K + Na) indicates evidences of cation exchange and salt water intrusion. The (Ca–0.33*HCO3)/ SO4 plot indicates salt water intrusion for elevated SO4 levels rather than gypsum dissolution. The spatial distribution of total dissolved solid indicates the saline water encroachment along the SW part of the study area. As per sodium adsorption ratio (SAR), 50% of the samples with 10 SAR indicates that water is unsuitable for irrigation purposes. The residual sodium carbonate classification indicates that 50% of the samples fall in safe and 50% of the samples fall in bad zones and prolonged usage of this water will affect the crop yield. The Chloro Alkaline Index of water indicates disequilibrium due to a higher ratio of Cl > Na–K, indicating the influence of salt water intrusion. The Permeability Index of the groundwater indicates that the groundwater from the study area is moderate to good for irrigation purposes.

A comparative evaluation of heuristic and bivariate statistical modelling for landslide susceptibility mappings in Ghurmi–Dhad Khola, east Nepal

Abstract: Landslides are one of the major natural disasters that occur in the Himalayan range with recurring frequency, causing enormous loss of life and property every year. Preparation of landslide inventory maps and landslide susceptibility zonation maps are the important tasks to be taken into account initially for safe mitigation measures. The present paper focuses on landslide susceptibility maps of the Ghurmi–Dhad Khola area, east Nepal, using Geographic Information System. For this purpose, the landslide susceptibility maps are prepared by using the heuristic and bivariate statistical methods. The parameters considered for the study are slope angle, slope aspect, elevation, distance from drainage, geology, land cover, rock and soil type, and distance from faults and folds. The landslide susceptibility zonation map produced from the heuristic method shows that 42.59 % of the observed landslide falls under the very high susceptible zone and 33.00 % under the high susceptible zone. Likewise, the landslide susceptibility zonation map produced from the bivariate method depicts that 44.19 % of the observed landslide falls under the very high susceptible zone and 31.59 % under the high susceptible zone. Both the landslide susceptibility zonation maps are identical, and success rates of both the maps are above 80 %. While comparing the landslide susceptibility maps obtained from two different methods, about 78 % of the study area falls in the identical susceptible zones. Special attention should be taken into consideration for the construction works in the areas which have been spatially agreed as very high and high susceptible zones from both techniques. Moreover, these maps can be used for slope management, land use planning, disaster management planning, etc., by the concerned authorities.

Landslide vulnerability mapping using frequency ratio model: a geospatial approach in Bodi-Bodimettu Ghat section, Theni district, Tamil Nadu, India

Abstract: This research paper assesses the vulnerability of landslide for the Bodi-Bodimettu Ghat section, Theni district, Tamil Nadu, India, using remotely sensed data and geographic information system (GIS). Landslide database was generated using IRS-1C satellite LISS III data and aerial photographs accompanied by field investigations using differential global positioning system to generate a landslide inventory map. Topographical, spatial, and field data were processed to construct the spatial thematic layers using image processing and GIS environment. Twelve landslide-inducing factors were used for landslide vulnerability analysis: elevation, slope, aspect, plan curvature, profile curvature, proximity to road, drainage and lineament, land use/land cover, geology, geomorphology, and run-off. The first five factors were derived from digital elevation model, and other thematic layers were prepared from spatial database. Frequency ratio of each factor was computed using the above thematic factors with past landslide locations. Landslide vulnerability map was produced using raster analysis. The landslide vulnerability map was classified into five zones: very low, low, moderate, high, and very high. The model is validated using the relative landslide density index (R-index method). The consistency of R-index indicates good performance of the vulnerability map.

Earth dam site selection using the analytic hierarchy process (AHP): a case study in the west of Iran

Abstract: Earth dam site selection is one of the most important problems in water resources management. It depends on a set of qualitative and quantitative criteria, and they may even be in conflict with each other. This study aims to develop a multicriteria decision-making approach to locate the dam site and construct a multipurpose earth dam in Harsin City at the western part of Iran. For this purpose, firstly, the influential criteria for locating the earth dam site were determined using a comprehensive literature review and the experts’ opinions. Then, some watersheds in the surrounding areas of Iran’s Harsin City were studied and four feasible sites proposed. In the final stage, these sites, in order to construct a multipurpose earth dam, were prioritized using the analytic hierarchy process approach and the most optimal site was selected.

Diagnosis of groundwater quality and assessment of contamination sources in the Megara basin (Attica, Greece)

Abstract: In this study, hydrochemical analysis, statistical analysis and GIS database have been successfully used to explain the main factors and mechanisms controlling the distribution of major and trace elements in groundwater. The groundwater of Megara basin is subject to intense exploitation to accommodate all the water demands of this agricultural area. Water quality data obtained from 58 sampling sites of the Megara basin, aims to describe groundwater quality in relation to geology and anthropogenic activities. Factor analysis revealed that four factors accounted for 79.96% of the total data variability. The contribution of each factor at sampling sites was calculated. Evaluation of water samples by comparing quality standards and levels recorded in the literature for both drinking and irrigation uses is discussed.

Stability of slopes in a fire-prone mine in Jharia Coalfield, India

Abstract: Stability of slope in an opencast mine is always associated with safety and economics. The steeper slope is always preferred from economic point of view but prone to failure, whereas flatter slopes are uneconomical. A proper understanding of slope which will be a steep enough to be stable is required for safety, economy, and stability of men and machineries. The Rajapur opencast mine is one of the important mines in terms of good quality coal but has problems of water seepage, fire, and weak overburden materials. The existing coal mine has three working seams which are mostly thick and occur at shallow depths of about 50–60 m. Overall slope angle of the working faces as well as final pit is very steep which leads to failures. In the present paper, an attempt has been made to characterize the materials of the mine for simulation of existing slopes. The rock samples from the coal measures were collected to determine the petrophysical characteristics of various rock units. All the pertinent geological parameters from the exposed face were also collected during field visit to assess the slope mass rating (SMR). A two-dimensional finite difference tool was employed to simulate the existing slope geometry as well as relevant parameters of the rock units. The numerical simulation indicates various vulnerable points which are prone to failure as well as displacements at various points along the slope. The results of simulations are corroborated with the SMR value. The results are well matching with the field condition.

Air quality and elemental enrichment factors of aerosol particulate matter in Riyadh City, Saudi Arabia

Abstract: Air particulate matter (PM) samples were collected from June 2006 to May 2007 for determination of chemical elements. PM samples were taken in two size fractions (PM2.5 and PM10) with MiniVolume air samplers on rooftops of various buildings (15–25 m above ground) in the city of Riyadh. The samples were subjected to X-ray fluorescence analysis to measure major (Na, Mg, Al, K, Ca, Si, P, S, and Fe) and trace elements (Mn, Ni, Cu, Zn, and Ba). The results showed that the PM concentrations were higher for PM10 compared to PM2.5, indicating that the major PM source was local dust. Also the spatial distribution with high PM concentrations was observed in the south and southeast of the city and the lowest levels were in the center and northeast of the city. This spatial distribution was attributed to different factors such as wind direction and velocity, emission from cement factories, and the presence of buildings, trees, and paved streets that reduce the amount of dust resuspended into the atmosphere. The air quality of the city was found to range from good to hazardous based on PM2.5, and from good to very hazardous based on PM10. The element-enrichment factors revealed two element groups according to their changing spatial behavior. The first group showed no significant spatial changes indicating they have the same common source. The second group (mainly S and Ni) exhibited significant changes as expected from anthropogenic inputs. The origin of S is possibly a combination of minerals (CaSO4) and fossil fuel combustion. The source of Ni is probably from fossil fuel combustion.

Spatial assessment of desertification in north Sinai using modified MEDLAUS model

Abstract: This study aims to use spatial analyses and a geographic information system (GIS) to assess the environmental sensitivity for desertification in the north Sinai Peninsula, Egypt. Based on the Mediterranean Desertification and Land Use (MEDALUS) approach and the characteristics of the study area, a regional model was developed using GIS. Five main indicators of desertification including soil, climate, erosion, plant cover, and management were considered for estimating the environmental sensitivity to desertification. A spatial analyst extension Arc-GIS 10 software was used for matching the thematic layers and assessing the desertification index, of which the map of environmentally sensitive areas of the north Sinai Peninsula is produced. The obtained data reveals that 65 % of north Sinai is characterized by very severe sensitivity to desertification while the low sensitive one exhibits only 1.2 %. The moderately sensitive area occupies approximately 23 % of the study area. ETM+ and SPOT images are recommended to monitor sensitivity. The MEDALUS model was developed under the Egyptians to assess desertification sensitivity.

A study on the status of fluoride ion in groundwater of coastal hard rock aquifers of south India

Abstract: India has an increasing incidence of fluorosis, dental and skeletal, with nearly about 62 million people at risk. High fluoride groundwaters are present especially in the hard rock areas of the country. This paper analyzes the most extensive database on fluoride and other chemical constituent distribution in the coastal hard rock aquifers of Thoothukudi district. A total of 135 samples were collected and analyzed for major cations and anions to assess the geochemical process. The fluoride concentration in drinking waters varied from BDL to 3.2 mg l−1 in the study area. Majority of the samples do not comply with WHO standards for most of the water quality parameters. The saturation index of fluorite saturation index was used to correlate with F− to identify their relationship to increase of fluoride levels. The correlation between the F− concentration and the water type was also attempted. Spatial distribution of fluoride in groundwater was studied to understand the influencing factors. The relationship of F− with HCO− 3, Na+ and pH concentrations were studied and found that HCO− 3, has good correlation with F− than the other parameters.

Study of the influence of geotechnical parameters on the TBM performance in Tehran–Shomal highway project using ANN and SPSS

Abstract: Alborz twin tunnel along with an exploratory or service tunnel between the two main tunnels, are the longest tunnels section in Tehran–Shomal highway with 6.3 km length. The service tunnel is designed to be used for geological investigations, ventilation, transportation during the construction of main tunnels, water drainage, ground improvement by grouting, and emergency exit. An open tunnel boring machine (TBM) of Wirth Company was used to drive this service tunnel. With regard to the fact that in such mechanized tunneling projects, performance of the TBMs is of the most importance, which affects the economy and timing of the projects; on the other hand, geotechnical conditions of the region play a significant role in this respect, this effect was investigated during this study. In this study, two main elements of the TBM performance including the rate of penetration and utilization factor were investigated using artificial neural network and Statistical Package for Social Sciences. It is shown that geotechnical conditions have considerable effect on the rate of penetration. Whereas, utilization is largely affected by management and non-rock mass-related parameters including delays, wasted times, maintenance, labor, etc. With regard to the available data, four parameters including uniaxial compressive strength (UCS), friction angle, Poisson’s ratio, and cohesion were selected to be studied. Based on assessments conducted using these approaches, the rate of effectiveness of four selected parameters on penetration rate, in a descending order, was as follows: UCS, friction angle, Poisson’s ratio, and cohesion. For increasing utilization, it was concluded that minimizing time delays by good management is the most effective way. Furthermore, with regard to the relative error percentages and the coefficient of correlation of the input and output data, it was concluded that the method artificial neural network yields more reliable results than the statistical approach.

Major ion chemistry and identification of hydrogeochemical processes controlling groundwater in and around Neyveli Lignite Mines, Tamil Nadu, South India

Abstract: Groundwater geochemistry was studied in and around the Neyveli lignite mining region of Tamil Nadu, India. Representative groundwater samples (168) were collected from bore wells during June 2004, October 2004, January 2005, and March 2005 to broadly cover seasonal variation. Higher electrical conductivity values were observed in the southeastern and southwestern part of the study area. During the southwest monsoon (June) and postmonsoon (January) seasons, bicarbonate + chloride dominated the anions, with few representations for sulphate. Sodium + potassium were the dominant cations in all the seasons except in summer (March). The data reveals that the region is a complex hydrogeochemical system with proportional interplay of ions from leaching of ions, ion exchange, agricultural return flow, and stagnant waters. The influence of mine waters and weathering of minerals varies according to the season and spatial distribution of the sources. The water quality can be used for drinking and irrigation, except in a few locations.

Assessment of soil erosion risk using SWAT model

Abstract: Soil erosion is one of the most serious land degradation problems and the primary environmental issue in Mediterranean regions. Estimation of soil erosion loss in these regions is often difficult due to the complex interplay of many factors such as climate, land uses, topography, and human activities. The purpose of this study is to apply the Soil and Water Assessment Tool (SWAT) model to predict surface runoff generation patterns and soil erosion hazard and to prioritize most degraded sub-catchment in order to adopt the appropriate management intervention. The study area is the Sarrath river catchment (1,491 km2), north of Tunisia. Based on the estimated soil loss rates, the catchment was divided into four priority categories for conservation intervention. Results showed that a larger part of the watershed (90 %) fell under low and moderate soil erosion risk and only 10 % of the watershed was vulnerable to soil erosion with an estimated sediment loss exceeding 10 t ha−1 year−1. Results indicated that spatial differences in erosion rates within the Sarrath catchment are mainly caused by differences in land cover type and gradient slope. Application of the SWAT model demonstrated that the model provides a useful tool to predict surface runoff and soil erosion hazard and can successfully be used for prioritization of vulnerable areas over semi-arid catchments.

Simulation of water resources management scenarios in western Algeria watersheds using WEAP model

Abstract: The question of water constitutes a permanent challenge for the countries of North Africa in general and Algeria in particular. For over 20 years, western Algeria region had significant rainfall deficits that resulted in severe droughts, which seriously affected the water resources in terms of quality and quantity. This research presents one of the Water Evaluation and Planning (WEAP) model applications in watersheds of western Algeria. The model is applied to evaluate and analyze the existing balance and expected future water resources management scenarios by taking into account the different operating policies and factors that may affect demand until 2030. The results showed that neither domestic demand nor agricultural demand is met for the basis year 2006. The results also showed that domestic demand can be satisfied for the considered scenarios. Demand management and development of standard of living are the necessary procedures for proper management of the available resources. However, agricultural demand cannot be satisfied for Development of Large Irrigation System scenarios. The results confirmed that WEAP software offers a solid basis to assist planners in developing recommendations for future water resource management by revealing hot spots of action.