Geohazard assessment of sand dunes between Jeddah and Al-Lith, western Saudi Arabia

Serious hazards have taken place in urban areas and road construction in Saudi Arabia because of the presence of accumulations of drifting sand dunes. Several researches, which carried out investigative work to solve this problem, were reviewed. Three locations of dune fields along the area between Jeddah and Al-Lith were investigated. The dune forms was identified. Detailed field investigations showed that barchan dunes are dominant in the area. The sands from the studied locations were found to be similar in grain size and shape parameters. Mineralogically, the sand reflects the composition of the surrounding igneous and metamorphic rocks. Regression analyses were performed and empirical relationships between dune height, width, windward length, slip-face length, and rate of movements were developed. Relatively strong relations exist between these parameters. The most important geometric parameter controlling dune movement with wind speed and direction is determined to be the dune height. A reasonable similarity occurs between the barchan dunes in the study area and those existing in Al Nufud, Al Jafurah sand seas, and Khulays area. The studied dune fields pose some natural hazards on the roads, and the surrounding buildings and constructions in the villages along the area between Jeddah and Al-Lith, especially during wind storms.     

Near-surface foundation level assessment from seismic measurements: a case study of north Jeddah City,Saudi Arabia

In this study, a comprehensive assessment on the generation mechanism, distribution characteristics, and extension rules of structure cracks was conducted by in situ monitoring and field investigation in the Chengchao Iron Mine. Structure cracks are affected by many factors, e.g., surface deformation, structure strength, occurrence position, and machine vibration. They initially occur in a structure when the strength of the structure is not enough to resist the inner strain as surface deformation increases. In contrast, increases in width and length of structure crack exert stress release in the structure and thus decrease structure deformation surrounding the crack. A great ground crack may adversely aggravate structure cracking and release the stress of surrounding rock masses. In addition, micro cracks in rock masses provide favorable conditions for the generation and extension of cracks, resulting that cracks occur in shaft walls more easily and extend towards the deeper. The initial distribution of cracks is generally consistent with such micro cracks. Subsequently, cracks in deep rock masses will extend along the strike of the mined-out area as surface deformation increases. Sensibilities to cracking of structures are changed by their different strain resistances and become stronger from bolt-shotcrete shaft, bolt-shotcrete tunnel, and brick-concrete building to brick wall. Based on distribution characteristics of cracks and wave velocity in rock masses, the overlaying strata affected by underground mining can be divided into four zones: broken zone, broken transition zone, crack generation zone, and micro deformation zone.     

Stratigraphic architecture of the fluvio-lacustrine deposits, Bathan Formation, Al-Rehaili area, North Jeddah, Saudi Arabia

A siliciclastic-dominated succession (～11 m thick) underlying Harrat Rahat, belonging to the Miocene–Pliocene Bathan Formation is recently exposed at Al-Rehaili area, North Jeddah, Saudi Arabia. It covers a wide spectrum of grain sizes varying from clay-rich mudstones to cobble grade conglomerate and consists of a variety of facies vary from fluvial to marginal and open lacustrine deposited in a half-graben basin formed along the eastern margin of the extensional Red Sea Basin. Field-based sedimentologic investigation enables to identify ten facies grouped into three facies associations (A–C). The depositional history is subdivided into two stages. The first stage represents deposition in gravel to sand-dominated fluvial system sourced from a southern source and grade northward into lacustrine delta and open lacustrine setting. The second stage on the other hand includes deposition of fluvial channels running in E–W direction with attached bank sand bar. Sequence stratigraphic interpretations of the lacustrine deposits enable to identify three unconformity-bounded sequences (SQ_1–3). The basal sequence is incomplete, consisting of three aggradationally to progradationally stacked delta plain and delta front parasequences. The second sequence is sharply and erosively overlying a red paleosol bed that defines the upper boundary of the first sequence. It includes two system tracts; upward-fining and deepening lacustrine offshore mudstones of the transgressive system tracts unconformably overlain by red paleosol of the regressive systems tracts. The top of this sequence is delineated at the sharp transgressive surface of erosion at the base of delta mouth bar deposits of sequence 3. Changes in the accommodation and sedimentation rates by basin subsidence under the influence of tectonics and sediment compaction and loading as well as climatic oscillation between semi-arid to arid conditions were the major controls on the fluvio-lacustrine sedimentation and their facies distribution. Tectonic reorganization of the drainage system resulted in the formation of E–W flowing fluvial streams in the second stage.     

Environmental assessment of soil,groundwater, and surface water quality in the south of the Riyadh,Saudi Arabia

To understand the impact of the influence of treated wastewater, a study was undertaken in the downstream side of Wadi Hanifa in the southern part of Riyadh City in Saudi Arabia. Chemical elements from 17 groundwater samples, 9 surface water samples (treated wastewater), and 14 soil samples were analyzed. Water facies analyses showed that both groundwater and surface water belong to the SO₄-Cl class. However, the groundwater is characterized by high salinity (average value of 3547 mg/l), which may be result of the greater rock-water interaction and limited rainfall recharge. The NO₃ values are also high in the groundwater samples (average value of 40 mg/l) and are mainly attributed to the agricultural practices in the study area. The surface water samples (treated wastewater from the plant) shows an average salinity value of 1232 mg/l and is better suited for irrigation purposes. Heavy elements analyzed in the soil samples show high concentrations of all the elements except Mn and Ni as compared to their background concentration. Enrichment factor and index of geoaccumulation calculated from the soil samples indicate that they are severely enriched with respect to Cd and Se. The spatial distribution maps were prepared based on kriging interpolation technique to estimate the concentrations of the analyzed elements at unknown locations. The treated wastewater in the study area is better suited for agricultural and domestic activities as compared to groundwater.     

Multichannel analysis of surface waves (MASW) for seismic site characterization using 2D genetic algorithm at Bahrah area,Wadi Fatima,Saudi Arabia

The present study deals with the seismic site classification of Bahrah area, Wadi Fatima, to characterize the local site conditions. The dynamic behavior of sediments was studied by the application of surface wave inversion. The multichannel analysis of surface waves (MASW) shallow geophysical technique was utilized for site classification. MASW survey was carried out at 66 sites along with 13 seismic refraction profiles at suitable localities. MASW and seismic refraction profiles were processed and compared with the available borehole data. The integration of MASW techniques with seismic refraction and borehole data progressively enhanced the subsurface visualization and reliability of the shear wave velocity estimation in the subsurface in the study area. The subsurface shear-wave velocity model was achieved by the solution of an inverse problem-based dispersion of surface waves and propagation in a vertically heterogeneous medium. The 2D genetic algorithm was employed for the inversion of dispersion curves to obtain velocity and thickness of subsurface layers. The depth to engineering bedrock and velocity of shear waves in the first 30 m was deciphered and mapped. The depth of bedrock in study area varies from 4 to 30 m, and V _{S 30} ranges from 320 to 800 m/s. The most of study area falls in B and C class categories in addition to few sites of D class according to the NEHRP guidelines.     

Seismic vulnerability assessment in the new urban area of Diriyah Governorate,Riyadh, Saudi Arabia

Nine seismic refraction profiles were conducted and processed to study the near-surface sediments in the new urban area of Diriyah. The 2D geoseismic models illustrate two layers: a surface layer of soft sediments and weathered to hard limestone bedrock. Moreover, microtremor measurements were performed at 38 sites for 40 min using three-component seismographs and processed to assess the peak spectral amplitude and the corresponding fundamental resonance frequency. The seismic vulnerability index at each measurement site was estimated. These results correlate well with the geotechnical borehole data. The north-western zone is highly vulnerable due to the great thickness of the soft sediments.     

Hydrogeology and hydrochemistry of a shallow alluvial aquifer,western Saudi Arabia

A hydrogeological and hydrochemical study was conducted on a shallow alluvial aquifer, Wadi Wajj, in western Saudi Arabia to assess the influence of protection measures on groundwater quality. The hydrochemistry was assessed up-gradient and down-gradient from potential contamination sources in the main city in dry and wet seasons prior to and after the installation of major drainage and wastewater facilities. Wadi Wajj is an unconfined aquifer where water is stored and transmitted through fractured and weathered bedrock and the overlying alluvial sediments. Natural recharge to the aquifer is about 5% of rainfall-runoff. Hydrochemistry of the aquifer shows temporal and seasonal changes as influenced by protection measures and rainfall runoff. Both groundwater and runoff showed similar chemical signature, which is mostly of chloride-sulfate-bicarbonate and sodium-calcium type. Groundwater downstream of the city, though of poorer quality than upstream, showed significant improvement after the installation of a concrete runoff tunnel and a wastewater treatment plant. Concentrations of many of the groundwater quality indicators (e.g., TDS, coliform bacteria, and nitrate) exceed US Environmental Protection Agency drinking-water standards. Heavy metal content is, however, within allowable limits by local and international standards. The chemical analyses also suggest the strong influence of stream runoff and sewage water on the groundwater quality.

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Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.

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Résumé Une étude hydrogéologique et géochimique a été menée sur l’aquifère phréatique alluviale Wadi Wajj dans l’Ouest de l’Arabie Saoudite afin d’évaluer l’influence de mesures de protection sur la qualité de l’eau souterraine. L’hydrogéochimie de l’eau a été étudiée en amont et en aval de sources potentielles de contamination dans la ville principale, pendant les saisons sèches et humides, avant et après l’installation de réseaux majeurs de drainage et d’eaux usées. L’aquifère Wadi Wajj est libre, l’eau est stockée et s’écoule dans les sédiments alluviaux et dans le socle fracturé et altéré sous-jacent. La recharge naturelle de l’aquifère représente 5% des eaux de pluie et de ruissellement. L’hydrogéochimie de l’eau de l’aquifère montre que les changements saisonniers et temporaires sont influencés par les mesures de protection et par le ruissellement des eaux pluviales. L’eau souterraine et l’eau de ruissellement ont présenté le même faciès chimique, de type bicarbonatée-sulfatée-chlorée et calco-sodique. En aval de la ville, l’eau souterraine, bien que de moins bonne qualité qu’en amont, a présenté une nette amélioration après l’installation d’un système de récupération et d’une station de traitement des eaux usées. Les concentrations de plusieurs paramètres indicateurs de la qualité de l’eau (tels que la charge totale dissoute, les coliformes, et les nitrates) dépassent les normes de potabilité de l’eau de consommation de l’agence américaine de la protection de l’environnement. Les teneurs en métaux lourds en revanche n’excèdent pas les normes locales et internationales. Les analyses chimiques indiquent aussi l’influence importante de l’écoulement par ruissellement et des eaux usées sur la qualité de l’eau souterraine.

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Resumen Un estudio hidrogeológico e hidroquímico fue hecho en un acuífero somero de Wadi Wajj, en Arabia Saudi oeste para evaluar la influecia de medidas de protección en la calidad del agua subterránea. La hidroquímica fue evaluada gradiente-arriba y gradiente-abajo de las fuentes potenciales de contaminación de la ciudad principal durante las estaciones seca y lluviosa, antes y después de la instalación de sistemas principales de drenaje y aguas servidas. Wadi Wajj es un acuífero no-confinado donde el agua es almacenada y transmitida a través de roca fracturada y meteorizada, y los sedimentos aluviales que le sobreyacen. La recarga natural del acuífero es de cerca del 5% de la precipitación-escorrentía. La hidroquímica del acuífero muestra cambios temporales y estacionales influenciados por las medidas de protección y la escorrentía de precipitación. Ambas, agua subterránea y escorrentía mostraron composición química similar, siendo mayoritariamente de tipos cloruro-sulfato-bicarbonato y sodio-calcio. El agua subterránea aguas arriba de la ciudad, aunque de calidad más pobre que aguas abajo, mostró significante mejoría después de la instalación de un tunel de concreto para escorrentía y una planta de tratamiento de aguas servidas. Las concentraciones de muchos de los indicadores de calidad de agua subterránea (e.g., STD, coliformes, y nitrato) exceden los estándares de la Agencia de Protección Ambiental USA para agua potable. El contenido de metales pesados está, sin embargo, dentro de los límites permisibles de los estándares locales e internacionales. Los análisis químicos también sugieren la fuerte influencia de la escorrentía y aguas residuales en la calidad del agua subterránea.

     

Hydrologic behavior and flood probability for selected arid basins in Makkah area, western Saudi Arabia

In arid regions, flash floods often occur as a consequence of excessive rainfall. Occasionally causing major loss of property and life, floods are large events of relatively short duration. Makkah area in western Saudi Arabia is characterized by high rainfall intensity that leads to flash floods. This study quantifies the hydrological characteristics and flood probability of some major wadis in western Saudi Arabia, including Na’man, Fatimah, and Usfan. Flood responses in these wadis vary due to the nature and rainfall distribution within these wadis. Rainfall frequency analysis was performed using selected annual maximums of 24-h rainfall from eight stations located in the area. Two of the most applied methods of statistical distribution, Gumbel’s extreme value distribution and log Pearson type III distribution, were applied to maximum daily rainfall data over 26 to 40 years. The Gumbel’s model was found to be the best fitting model for identifying and predicting future rainfall occurrence. Rainfall estimations from different return periods were identified. Probable maximum floods of the major wadis studied were also estimated for different return periods, which were extrapolated from the probable maximum precipitation.     

Quality assessment of groundwater at south Al Madinah Al Munawarah area, Saudi Arabia

Groundwater is the main source of irrigation within south Al Madinah Al Munawarah region. It is also an important source of drinking water in many areas including Madinah city. The wells installed in the aquifer of the study area (south Madinah city) are not currently regulated by the local authorities although they are a key component of water supply. The aquifers in the study area range from unconfined to semi-confined and confined. The main aim of this study is to assess the groundwater in the region for drinking and agricultural uses. For this purpose, hydrochemical analyses of major, minor and trace constituents and nutrients were performed on 29 groundwater samples from the aquifer located about 20 km south of Madinah. The recharge rate of the aquifer of the study area was estimated to be 6.58 % of the annual precipitation using the chloride mass-balance method. Chloride was positively correlated with major ions, which suggests that agricultural activities have some effect on groundwater chemistry through leaching of readily soluble salts from the soil zone. Groundwater of the study area is characterized by dominance of Na over Ca. Chloride was found to be the most dominant anion and replaced by HCO₃, thus reflecting geochemical evolution in the study area. The groundwater of the study area is not safe for drinking but can be safely used for salt-tolerant crops.     

Geochemical variation of the groundwater characters along Wadi Qudaid,northeast Jeddah,westcentral Arabian Shield,Saudi Arabia

Wadi Qudaid is present about 120 km northeast of Jeddah, Saudi Arabia. The area includes Precambrian Arabian Shield, Tertiary sedimentary rocks, Tertiary basic volcanics (harrat), and finally Quaternary wadi deposits which represent the main aquifer of Wadi Qudaid area. The present study indicates the presence of pronounced geochemical variations in the groundwater characters along the main channel of Wadi Qudaid from the southwestern part (downstream) to the northeastern (upstream) part. The groundwater-bearing horizon is thicker in the downstream part than the upstream part. The study also revealed that the groundwater is of good quality in the upstream (NE) part than the downstream (SW) part. This is related to the addition and depletion of many elements during the groundwater trip from NE to SW and the addition and depletion of some elements. The downstream part is of high hardness and TDS when compared with the upstream part. Also, the downstream part is of high bisnous element (As, Co, Ni) than the upstream part. The groundwater of the southwestern part of Wadi Qudaid are free from the following elements: i.e., Al, Mn, Fe, Ni, Cu, Zn, and Pb.     

Dam break analysis and flood disaster simulation in arid urban environment: the Um Al-Khair dam case study,Jeddah, Saudi Arabia

Natural Hazards - This study used a simulation methodology for dam break analysis and flood simulation in an urbanized arid region, namely Um Al-Khair dam in Jeddah, Saudi Arabia. The analysis was...     

Interpretation of a seismic-refraction survey across the Arabian shield in western Saudi Arabia

In February 1978 seismic-refraction profiles were recorded by the U.S. Geological Survey along a 1000 km line across the Arabian Shield in western Saudi Arabia. This report presents a traveltime and relative amplitude study in the form of velocity-depth functions for each individual profile assuming horizontally flat layering. The corresponding cross section of the lithosphere showing lines of equal velocity reaches to a depth of 60–80 km.The crust thickens abruptly from 15 km beneath the Red Sea Rift to about 40 km beneath the Arabian Shield. The upper crust of the western Arabian Shield yields relatively high-velocity material at about 10 km depth underlain by velocity inversions, while the upper crust of the eastern Shield is relatively uniform. The lower crust with a velocity of about 7 km/s is underlain by a transitional crust-mantle boundary. For the lower lithosphere beneath 40 km depth the data indicate the existence of a laterally discontinuous lamellar structure where high-velocity zones are intermixed with zones of lower velocities. Beneath the crust-mantle boundary of the Red Sea rift most probably strong velocity inversions exist. Here, the data do not allow a detailed modelling, velocities as low as 6.0 km/s seem to be encountered between 25 and 44 km depth.     

Evaluation of the water resources potential at Dahaban region, western Saudi Arabia

Shallow renewable groundwater sources have been used to satisfy the domestic needs and the irrigation in many parts of Saudi Arabia. Increased demand for water resulting from accelerated development activities has placed excess stress on the renewable sources especially in coastal aquifers of the western region of Saudi Arabia. It is expected that the current and future development activities will increase the rate of groundwater mining of the coastal aquifer near the major city Jeddah and surrounding communities unless management measures are implemented. The current groundwater development of Dahaban coastal aquifer located at alluvial fan at the confluence of three major Wadis is depleting the shallow renewable groundwater sources and causes deterioration of its quality. Numerical models are known tools to evaluate groundwater management scenarios under a variety of development options under different hydrogeological regimes. In this study, two models are applied—the MODFLOW for evaluating the hydrodynamic behaviors of the aquifer and MT3D salinity distribution to the costal aquifer near Dahaban town. The models’ simulation evaluates two development scenarios—the impact of excessive abstraction and the water salinity variation keeping abstraction at its current or increases in levels with or without groundwater recharge taking place. The simulation evaluated two scenarios covering a 25-year period—keeping the current abstraction at its current and the other scenario is increasing the well abstraction by 50% for dry condition (no recharge) and wet condition (with recharge). The analysis reveals that, under the first scenario, the continuation of the current pumping rates will result in depletion of the aquifer resulting in drying of many wells and quality deterioration at the level of 2,500 ppm. The results are associated with the corresponding salinity distribution in the region. Simulation of salinity in the region is a density-independent problem as salt concentration does not exceed 2,000 ppm, which is little value compared with sea salinity that amounts to 40,000 ppm. It is not recommended to increase the pumping rate than the current values. However, for the purpose of increasing water resources in the region, it is recommended to install new wells in virgin zones west of Dahaban main road. Maps of high/low potential groundwater and maps of salinity zones (more or less than 1,000 ppm) are provided and could be used to identify zones of high groundwater potential for the four studied scenarios. The implemented numerical simulation of Dahaban aquifer was undertaken to assess the water resources potential in order to reduce the depletion of sources in the future.     

Lithostratigraphy and standard microfacies types of the Neogene carbonates of Rabigh and Ubhur areas, Red Sea coastal plain of Saudi Arabia

The Neogene carbonate rocks have relatively small exposure relative to the siliciclastic and evaporite rocks in Rabigh and Ubhur areas, north Jeddah, Red Sea coastal plain of Saudi Arabia. The Miocene carbonates form small hills in both areas, which conformably overlie the siliciclastics, whereas the Pleistocene coral reefs form terraces facing the Red Sea in Rabigh area. The Neogene carbonates are represented by the following microfacies types: (1) dolomitic, oolitic, foraminiferal packstone; (2) sandy, dolomitic, intraclastic, foraminiferal packstone; (3) dolomitic and oolitic wackestone; (4) dolomitic, foraminiferal, intraclastic wackestone; (5) dolomitic mudstone; (6) coral boundstone; and (7) grainstone. The diagenetic processes affecting these carbonates are compaction, dissolution, aggrading neomorphism, and replacement that took place during deposition, shallow burial, and uplift. Pervasive dolomitization by the seepage reflux mechanism is responsible for the mimic replacement of the calcite of the original component of the limestone with dolomite. Sediments, biota, and lithofacies characteristics of the studied carbonate rocks of Rabigh and Ubhur areas indicate the presence of three facies zones; these are (1) FZ 5 platform margin reefs, (2) FZ 6 (platform margin sand shoals), and (3) FZ 7 platform interior-normal marine. The standard microfacies types are represented by (1) SMF 12, limestone with shell concentration; (2) SMF 15, oolitic wackestone and packstone; and (3) SMF 18, bioclastic grainstone and packstone with abundant benthic foraminifera.