GROUNDWATER CONCENTRATION BENEATH SAND FIELDS IN THE WESTERN DESERT OF EGYPT: INDICATIONS BY RADAR IMAGES FROM SPACE
Sand accumulations in the Western Desert of Egypt are located within topographic depressions. The source of the sand appears to be the "Nubian Sandstone," which is exposed throughout the southern part of the desert. Satellite images, particularly radar data, reveal that sand- covered, northward-trending courses of dry rivers end at the depressions. The sand appears to have been deposited in inland lakes within the depressions, and was later shaped into dunes during dry climates by southward flowing wind. The depressions must have hosted great volumes of surface water during the wet climates. Much of that water would have seeped into the underlying rock through primary and/or secondary porosity to be stored as groundwater, which should be considered in economic development projects.
POTENTIAL AND APPLICATIONS OF RADAR DATA IN EGYPT
This paper introduces the basic concepts of radar imaging and radar-terrain responses. This includes the side-looking geometry, and electromagnetic and geometric interactions with the surface, that all distinguish radar images from images taken by other sensors such as Landsat. Radar images are reviewed and summarized with respect to detecting, mapping and interpreting structural landforms, subsurface features, dunes and vegetated regions. Example figures are given in each case, and comparisons are made with Landsat data to illustrate the subsurface mapping principle. Examples of artifacts that may be present in radar data (such as speckle and layover) are also included to avoid their misinterpretation as "real" features. Finally, techniques of image processing and radar interferometry are discussed. The aim is to guide the reader in interpreting and understanding radar images in desert areas.
REMOTE SENSING APPLICATIONS FOR CHANGE DETECTION IN THE COASTAL REGION OF THE NILE DELTA, EGYPT
The coastal district between Baltiem and Gamasa towns represents the only remaining desert area in the northern part of the Nile Delta. This area covers about 450 km2 , and is occupied by various types of landforms including beach, sandy plain, sand dune, wetland, sabkha, and evaporite crusts. The development plan of this region is facing a number of constrains which affect negatively the sustainability of development activities in this area. These constrains include: coastal erosion and accretion, sea level rise, and sand dune encroachment. The negative impact of these phenomena has been studied, in detail, using the multi-temporal analysis of remote sensing data, as well as field and laboratory investigations. Monitoring changes in landuse-landcover has also been carried out using unsupervised classification of Landsat TM and SPOT images in years 1990 and 1995 respectively.
STRUCTURAL AND TECTONIC EVOLUTION OF THE SINAI PENINSULA, USING LANDSAT DATA: IMPLICATIONS FOR GROUND WATER EXPLORATION
Analysis of Landsat images of the Sinai Peninsula, Egypt, reveals three main structural provinces characterized by different styles of deformation. In the south, Precambrian highlands are complexly deformed by early ductile structures, and cut by mafic dike swarms. The main structures discussed include northwest- striking normal faults, and northeast-striking sinistral strike-slip faults, with several cross-faults. On the Egma and Tih plateaux, in the central Sinai, faults with similar orientations cut Maastrichtian strata, showing that they are post Cretaceous, and probably related to the opening of the Red Sea. In the northern Sinai, an active fold-thrust belt is associated with several large dextral strike- slip faults. This suggests that both were developed in a transpressional regime, probably associated with the rotation of the Arabian plate away from the African plate, with the Sinai Peninsula as a microplate wedged between them. Many of these brittle structures control surface runoff and may host fracture zone aquifers, potentially holding large quantities of ground-water, which are recharged during humid climate intervals. The major fracture zones will also serve as transmitters of water from the highlands in the south to the lowlands of the north. This concept should be considered in future ground-water exploration in the Sinai Peninsula.
QUANTITATIVE PHOTOLINEATION ANALYSIS AND SOME GEOMORPHIC AND STRUCTURAL ASPECTS OF THE GILF KEBIR AND ABU RAS PLATEAUS, SOUTH WESTERN DESERT, EGYPT
Satellite image analysis of the geomorphic expressions of the Gilf Kebir and Abu Ras plateaus shows that the Gilf Kebir plateau is primarily lithologically controlled and the Abu Ras plateau is primarily structurally controlled. Silicification and baking near lava flows at the topmost layer of the Gilf Kebir indurated the caprock especially at its western part. Absence of basalt occurrences in the Abu Ras accelerated the rate of erosion augmented by a dense set of fractures. An inferred NW-SE axis of slightly plunging anticlinal fold may have affected the area between the two plateaus. Two northeast-trending faults cut the fold and the mass in between is laterally displaced toward the southwest. Photolineation analysis of both plateaus indicated that NE and NNE trends are significant for the Gilf Kebir and NNW and NE trends are significant for the Abu Ras. A prominent N-S fracture separates Abu Ras into two elongated parts.
QUANTITATIVE STUDY OF THE FRACTURE PATTERN OF THE AREA AROUND THE WESTERN PART OF WADI EL- KHARIT, SOUTH EASTERN DESERT, EGYPT
Egypt is a part of the Northeast African craton which, during its geological history, underwent periodic marine transgressions from the ancient Tethys, situated to the north and northeast. Aerial photographs (scale 1:40,000) augmented by ground truth, are the main data acquisition medium used. The major fractures and faults observed in the studied area may be considered as belonging to two very broad age groups designated here as older and younger. The older fractures and faults are in most cases short dissecting lines which do not show apparent horizontal displacement, and they are restricted in occurrence to the basement rocks. They include a prominent NE-SW set and a less abundant older ENE-WSW set. The younger fractures and faults are mostly traced as continuous lineaments extending for long distances that may reach in cases more than 100 Km and occasionally, they show vertical displacements. These fractures and faults include two main sets which strikingly simulate the structural trends of the Red Sea and the Gulf of Suez, with the most abundant set trending N 25° to 30° W : (NNW-SSE), whereas the second next in abundance set trends N45° to 50° W (NW-SE). The common occurrence of these two sets indicates that this area has been under the influence of the tectonic forces leading to the development of the Red Sea. During the formation of the ancestral Red Sea rift, a tensional force, affecting in NE-SW orientation, gave rise to a number of normal faults and fractures mainly trending NW, NNW and WNW, rejuvenating the old trends of the deep-seated tectonic zones. A rejuvenated phase of the tensional stress affected the area after the deposition of the lower Tertiary units and gave rise to more faults and fractures trending mainly NW, NNW and WNW, as the older ones.
SEDIMENTOMORPffiC CLASSIFICATION OF THE NW SINAI DUNE FIELDS AS REVEALED BY THE SA TELLITEIMAGES
This study deals with the preliminary assessment of the recent sediments that cover and surround the North Sinai Agricultural Development Project and the International Coastal Highway. This area is located mostly within the north- western Sinai dune field and EI-Tina mud flat, where their sedimentological nature may adversely impact the sustainability of the ongoing and planned development activities. Such an impact may result from the aeolian processes within the dune sedimentary cover (deflation, transportation and deposition of sand due to the action of winds on dry, loose exposed sediments), as well as the geotechnical conditions and tectonic potentialities within EI- Tina plain. The sedimentomorphic characterisation of the studied area entails the identification and classification of the sedimentary cover on the basis of its sedimentological and geomorphologic nature and the geographic delineation of each of the identified sedimentomorphic classes. An accurate delineation of the various sedimentomorphic facies that may cover a particular area and thorough understanding of their characteristics as well as the sedimentological processes that act upon them are considered as a prerequisite for a diligent and efficient assessment of the suitability of this area for specific development activity. These are also required for the prediction of future natural sedimentological hazards, and the design of suitable mitigation and protection measures. The present sedimentomorphic classification was performed on the basis of visual interpretation of hard copy satellite images (1992), aided with limited ground truth. Therefore, these results should be considered tentative and should be thoroughly reviewed and updated through detailed field surveys and sedimentological analysis for more accurate classification.
CHANGE DETECTION OF THE WESTERN PART OF EL-FAYOUM AREA AND EL-RAYAN LAKES USING MULTITEMPORAL TM DATA
One of the most significant benefits afforded by repeated satellite coverage is the ability to detect changes over specified period of time. The consistent satellite digital image quality makes it easy amenable for computer-aided analysis. The aim of the present study is two folds, first is a comparative study to investigate the use of the multitemporal satellite remotely sensed data with various change detection techniques. The second objective is the specific interest in detecting the change in the western part of EI-Fayoum area and EI-Rayan lakes. Two Landsat Thematic Mapper (TM) scenes acquired on 4 September 1987 and 3 August 1990 covering the study area have been processed (geometrically corrected and radiometrically balanced) and used for both visual interpretation and digital change detection mapping. The results of applying image differencing, image ratioing and unsupervised classification techniques show that a number of change areas including water and agriculture land were successfully detected. There were no substantial differences between the first two techniques in detecting such changes. Moreover, statistical estimation of these changes has been carried out.
HYDRO LOG I CAL IMPACT AND ASSESSMENT OF MORPHOMETRIC ASPECTS OF WADI AL-ASYUTI BASIN, EASTERN DESERT, EGYPT
Geomorphological, lithological and structural characteristics of the hydrographic basin of Wadi Al-Asyuti (6162 km2 ) were analyzed and evaluated to determine their impact on the surface drainage system. Quantitative morphometric approach was pursued to assess the hydrologic response, and to determine the runoff and flood potential of this basin. The calculated morphomertic parameters were applied on the last thunderstorm that took place on November 1st, 1994 to forecast numerically the hydrologic variables of the surface runoff. Practical alleviative measures are suggested to minimize the flash flood hazards, impound the storm water, and enhance the replenishment of ground water. In the light of this, potential target sites for wells are appraised and sorted out, priority-wise, into four orders.
USE OF SPACE IMAGERY AND AERORADIOMETRY FOR THE DELINEATION OF SOME GEOLOGIC ASPECTS OF THE WADI EL- ALLAQI AREA, SOUTH EASTERN DESERT, EGYPT
The Wadi EI-Allaqi area is located in the south Eastern Desert of Egypt (Lat. 22° 00' to 23° 00' N, Long. 33° 00' to 34° 30' E). The area has been studied geomorphologically, photogeologically, and structurally based on Landsat imagery and aeroradiometry. The geomorphological study of Wadi EI-Allaqi drainage basin revealed that there are eight large drainage sub-basins. These sub-basins can provide a limited water supply in any future planning for cultivation the lower plain of the Wadi EI-Allaqi or part of it. Photogeological and aeroradiometrical interpretations assisted in producing a new geological map of the area. Some lithiologic units and geological contacts were accordingly added. The study concluded that the area was subjected to different phases of deformation.
MORPHOTECTONICS OF GABAL ZEIT -ESH MELLAHA REGION (EASTERN DESERT, EGYPT) USING REMOTELY- SENSED DATA
Gabal Zeit-Esh Mellaha region in the southwestern Gulf of Suez has been studied using Landsat (TM&MSS) images and aerial photographs followed by detailed field work to demonstrate the influence of rift tectonics on its landforms. Vertical movements along the NW normal faults bounding the blocks in the basement, have significantly controlled the geomorphology of the study area. The NW trending fault- bounded blocks seem to have been rotated about horizontal axes causing tilting of the Precambrian basement rocks and their overlying sedimentary cover towards the southwest. Most of the drainage is structurally controlled in the basement but braiding and fanning characterize the alluvial plains. Different morphotectonic units viz. fault-scarp, piedment, alluvial fan, cuesta, inselberg, butte, badland and raised beaches have been distinguished and mapped and their morphotectonic evolution is dealt with. Alluvial fans developed along active NW fault scarps seem to have coalesced to form the bajadas of Tarbul and Gemsa piedment plains. They gave thick sequences of syntectonic sediments on the downthrown sides of major faults. Areal distribution and shapes of these fans and fault scarps reflect more neotectonic activity along Gabal Zeit and Esh Mellaha fault scarps which show more sharpness and straightness. Morphotectonic landforms and mountain-front sinuosity have been useful in regional evolution to identify relative tectonic activity in the study area. Moreover, bajadas present excellent geological conditions for groundwater accumulation in large quantities which could help in the future development of the concerned region. However, detailed hydrogeological studies are recommended. The present work emphasizes the significant value of remotely-sensed data for morphotectonic mapping and tectonic activity.
IMPACT OF GEOMORPHOLOGICAL HAZARDS ON EL-MOKATTAM AREA, EGYPT
The effect of natural disasters in establishing new settlements in Egypt is aggravated by the often-noted lack of environmental awareness, insufficiency of warning systems, virtual lack of capacity for recognition of hazards, and lack of infra-structures for disaster mitigation. The present study deals with hazards that have occurred already in El-Mokattam area and provides recommendations to minimize future risks. Physiographically, Gabal EI-Mokattam comprises three fault scarps forming three stepwise features that are known as; lower-, middle- and upper- plateaux belonging to the Middle and Upper Eocene. Geomorphological studies enabled delineation of the hazards and disasters localities in G. EI-Mokattam of rockslides, rock falls and slumps. The escarpment slope of the upper plateau varies due to lithological variation; where the hard rocks exhibit steep slope( > 70°), and the clastic rocks reflect gentle slope (>30°). Limestone fractures with nearly right angle sets forming blocks are common. The fractures are exploited pass ways of water and movements, also seeped water yields greased top bedding plane surfaces on soft clastics on which limestone blocks move. Very steep slope (70° - 90°) fault scarps and fault intersections and parallel fault swarms increase the risk of hazards. Due to the new constructions at El-Mokattam area without careful planning and execution of the infra-structures, infiltration of sanitary water to the bed rocks assists in deteriorating the geological environment of the area.
NEURAL NETWORK DESIGN FOR LAND- COVER CLASSIFICATION OF QENA REGION USING TM DATA
The main objective of this work is to design, implement, and validate Neural Network (NN) technique in land-cover classification (main classes and subclasses). The study area (Qena region) has been selected to include different five land- cover features (urban, water, soil, desert and sand, and agriculture) with twenty subclasses. The first phase of this work involved the adaptation of the network parameters for optimizing stability and achieving minimum output error. The second phase was to validate the results. Supervised classification with selected threshold values for narrowing the deviation of each class has been performed considering the output as a reference image. Accuracy Definition Model (ADM) has been developed for accuracy validation of the NN classification. The output of this research is an accuracy percentage for each assigned class.
VISUAL ANALYSIS OF REMOTELY SENSED DATA FOR SOIL MAPPING AND LAND CAPABILITY CLASSIFICATION
Visual analysis of remotely sensed data has been followed in order to map the soils of an area along the eastern shore of the Gulf of Suez. The area extends along the Gulf from north of Ras Abu-Rudeis to Ras Gihan in the south. The produced map shows sixteen mapping units representing different landforms and related soils of the area. Plains, deltas, alluvial fans, wadis, steep upland, foot slope, denuded hills, hills and plateaux were mapped and characterized. The land capability classification reveals that the soils of the study area belong to classes IV, V and VI. The capability indices of the soils of class IV range between 39.0 and 25.8, whereas indices for soils of class V fluctuate from 15.2 to 11.5 and those of class VI range between 9.2 and 7.3.
SOIL SPECTRAL REFLECTANCE BEHAVIOUR AS AFFECTED BY SOME SOIL CONSTITUENTS
A number of 24 topsoil samples were collected from Wadi El- Natrun, north and middle Delta, Ismaillia and EI-Fayoum depression. The spectral reflectance of these samples were measured at different wavelengths. The spectral signature of all investigated soils matches the commonly known general trend of the soil spectra. Clay and organic matter contents show negative and significant correlation coefficients with soil reflectance. Correlation coefficient values increase with increasing wavelengths from 360 to 700 nm for both clay and organic matter contents. Generally, there are negative relationships between total amorphous iron oxides and available iron from one side and all measured reflection at different wavelengths from the other side for the studied soil. types. For coarse-textured soils, the highest correlation coefficient value of total iron has been found at 500 nm. The highest correlation coefficient of amorphous iron oxides content is at 560 nm and that of available iron is recorded at 700 nm. Whereas, for fine textured soils, the highest correlation coefficient values have been recorded at 660 nm for total iron oxides, 400 nm for amorphous iron, and 700 nm for available. Soil colour value has positive highly significant correlation with soil reflectance at all considered wavelengths. Whereas, soil colour chroma shows positive insignificant correlation coefficient. The multiple linear regression equation demonstrates 95 % of the relationship between soil reflectance and soil constituents at 560 nm in case of coarse textured soils and 93 % at 700 nm for fine textured soils. Partial correlation analysis shows that amorphous iron oxides play the most effective role in reflection of the studied coarse textured soils, but total iron oxides are the most influencing constituent on reflection of the fine textured soils.
A CONTRIBUTION TO THE GEOLOGY OF DALMA AND SIR BANI YAS ISLANDS, UNITED ARAB EMIRATES
Dalma and Sir Bani Yas Islands are typical examples of the salt diapirs belonging to the Southeastern Zagros-Arabian Gulf-Interior of Oman evaporite province (southern Arabian Gulf salt basin). The central parts of the two islands are occupied by rocks of the Hormuz Complex (Cambrian-Infracambrian). This complex includes a great variety of sedimentary and igneous rocks that are present as blocks of different sizes in salt and gypsum/ anhydrite (Sir Bani Yas Island) or gypsum/anhydrite (Dalma Island) host. The most common sedimentary types are dolomites, limestones, and sandstones, whereas the igneous rocks are represented by bimodal volcanics that mainly include rhyodacite, dacite porphyry, dolerite, and tuffs. These are carried up by a multicoloured gypsiferuos sandstones and conglomerates. The blocks, constitute the summit of the numerous conical hills present at the central parts of the islands. The foothills of these highs, as well as the floor of the central parts of the islands are occupied by the multicoloured gypsiferuos sandstones and conglomerates. Tertiary and Quaternary rocks bordering the Hormuz Complex on both islands are represented by disturbed Pleistocene miliolite-bearing calcareous sandstones, and Holocene fluviatile deposits, beach sands, and reefs. These stratigraphic relations suggest that the salt diapirism is post- Miocene in age. A supervised classification of 1994 SPOT images covering the two islands, guided by surface geology, was used to outline the distribution of the different rock types, to study the geomorphological and structural features, and to construct geological maps for the two islands.
APPLICATION OF REMOTE SENSING TECHNIQUES TO A HYDROGEOLOGICAL INVESTIGATION OF SAND DUNES SOUTHWEST OF AL AIN CITY, UNITED ARAB EMIRATES
Remote sensing techniques were applied to distinguish the variations in the hydraulic properties of sand dunes and interdune areas southwest of Al Ain city, United Arab Emirates. The interdune areas were classified according to their soil- moisture content (%) into four classes: C1 (standing water), C2 (near- surface groundwater; >50 % soil moisture), C3 (50-25% soil moisture) and C4 ( >25 % soil moisture). According to uniformity coefficient (Cu ). and infiltration rate (Ir ), sand dunes were subdivided from east to west into three classes: C5 , C6 and C7 , with high (Cu ) and low (Ir ) in the east and low (Cu ) and high (Ir ) in the west. The (Cu ) of both sand dunes and interdune areas decreases from east to west, with increasing effective porosity (ne ), infiltration rate (Ir ) and hydraulic conductivity (K) of sediments. These conditions favour higher groundwater recharge from rainwater in the western part of the study area than the eastern part. The total volume of natural evaporation from standing water (class C1 ) and near- surface groundwater (class C2 ) within the study area, calculated from the output of remote sensing classification, is 6.35 x 106 m3 /yr.
MORPHOMETRY, SURFACE RUNOFF AND FLOOD POTENTIAL OF MAJOR DRAINAGE BASINS OF AL AIN AREA, UNITED ARAB EMIRATES
Topographic maps and satellite images, in addition to the records of 5 stream gauges and 11 meteorological stations, were employed to study the morphometry, surface runoff and flood potential of the major drainage basins in AlAin area, United Arab Emirates (U. A. E.). There are two systems of drainage basins; one is dissecting the Oman mountains in the east and the other is affecting Jabal Hafit in the west. Bifurcation ratio (Rb ) of drainage basins in the Oman mountains, east and northeast of Al Ain, varies between 2.0 and 5.6, indicating very high to very low risk of flash flooding. The Rb of Jabal Hafit basins ranges from 2.8 to 3.7, suggesting very high to moderate risk of flash flooding. Basins with low drainage density (Dd <1.7) are predicted to have high infiltration rate, long overland flow, and low risk of flash flood, whereas the basins of high Dd (>2.4) are expected to have low infiltration rate, short overland flow, and high risk of flash flood. The basin relief (Br ) of Oman mountains basins varies between 100 m at wadi mouth and 800 m at headwater divide, while the Br of Jabal Hafit basins ranges from 300 to 800 m. Wadis of Ajran, Al Ghayl and Al Ashkhar have the highest Br values (moderate to high flood potential), whereas wadis of Muraykhat, Sidr and Khubayb have the lowest Br (low to moderate flood potential). The shapes of the drainage basins within the study area are circular (Wadi Al Ain East and Wadi Shik), elongated (Wadi Ajran and Wadi Muraykhat) and triangular (Wadi Musayliq and Wadi Al Ashkhar). According to shape, Wadi Al Ain East and Wadi Shik basins are more favorable for flash floods than the other basins. Rainfall records and discharge data of gauging stations reveal that the minimum annual rainfall which can produce surface runoff on drainage basins of the Al Ain area is about 75 mm in the Oman mountains and 90 mm in Jabal Hafit. The calculated average annual runoff ranges from 0.25 million cubic meters (MCM) in the southwest to 3.00 MCM in the northeast. The average annual runoff depth for the 1981-1990 period ranges from 5 mm in the southwest to 20 mm in the northeast. The percentage of rainfall as runoff varies between 7.2 % (Wadi Ain Al Faydah) in Jabal Hafit basins and 18 % (Wadi Al Bih) in the basins of the Oman mountains. Wadi Sidr of the Oman mountains and Wadi Ain Al Faydah of Jabal Hafit are the basins with the highest flood potential within the study area. In contrast, Wadi Muraykhat and Wadi AlAin West are the basins with the lowest flood potential.
A NOTE ON THE PROSPECTING FOR RADIOACTIVE MATERIAL AND BLACK SANDS IN THE CENTRAL EASTERN DESERT OF EGYPT
Within the frame of the project Prospecting for radioactive material in the Central Eastern Desert of Egypt a region between Quseir and Mersa Alam was studied in detail. Field investigations showed that the highest anomalous concentration of radioactivity (as they appear from the various shadows of color on the processed map and checked in the field) are associated with the following exposures:
i) alkali granitic rocks of the Kadabora area,
ii) granitic rocks at the northern part of Gebel Um Naggat,
iii) The basal Miocene formations at the entrance of Wadi Essel (in which celesite and lead-zinc are known), in the area between wadi Essel and Wadi El Sharm El Bahari, at Wadi El Sharm El Bahari, at Wadi El Sharm El Qibili, at Wadis Wizr and Um Gheig. Chemical analysis of representative samples reveals the presence of high uranium contents (relative to the reference background level values given by Turekian and Wedepohl, 1961) in the following localities:
i) Um Naggat alkali granite: 49.19 ppm (3 ppm background level),
ii) Wadi Wizr altered fault zones: 30.5 -53.23 ppm (1.3 ppm backgroundlevel),
iii) Wadi Essel altered mineralized fault zones: 11.89 ppm (1.3 ppm background level),
iv) Wadi El Sharm El Qibli: 14.64 ppm (1.3 ppm background level).
In addition, the prepared digitized images and maps revealed the presence of considerable concentrations of black sands within in the coastal sands and dunes. Heavy mineral studies of representative samples gave the following encouraging results:
- Average total heavy minerals content of sediments: up to 12%.
- Opaque minerals: up to 50 % of the heavy fraction,
- ZTR (zircon, tourmaline and rutile): up to 4% of the heavy fraction.
Detailed mineralolgical and geochemical studies on the uraniferous basal Miocene clastic/carbonate localities and the coastal black sands are being carried out by the working group of the National Authority for Remote Sensing and Space Sciences (NARSS).