Volume 8 ,2006

Landsat ETM+ fltered image, spectral bands 7, 4, 3 (R, G, B) showing the Greater Cairo Area, acquired in 2003.

Utilization of Landsat-7 ETM+ Imagery and Seismic Hazard Assessment for the Urban Planning: A Case Study from El-Amal New City, East Cairo, Egypt

Geological interpretation using Landsat- 7 ETM+ imagery and seismic hazard assessment are applied to locate the favorable zones for urban expansion planning of EI-Amal New City (ANC), east Cairo, Egypt. Inspection of Landsat image, as well as the microtremors readings revealed the presence of swelling clay layer (over 200%), covering the central and the southern parts of the study area. Based on the fundamental mode of vibration and probabilistic Peak Ground Acceleration (PGA), the study area is divided into three seismic zones namely I, II & III. Zones II & III are the most favorable zones for urban expansion and construction. In these two zones engineers should take care that constructions can bear peak horizontal acceleration of 310 Gals (cm/sec1). The master plan for ANC is presented for the first time and is distinguished into three areas. The first area (A) is considered the most favorable site for the urban activities (housing and services) with total area of 1750 feddan sufficient to be inhabited by 150,000 inhabitants. The second area (B) is selected for large-scale compounds with heights of 2-3 storeys. Parts of the second area (B) and the third area (C) are suitable for industrial and agricultural use, respectively.

Environmental Land-cover/Land-use Change Detection in the Coastal Zone of the Gulf of Aqaba, Egypt, Using Multi-Temporal Landsat Imagery

The coastal zone of the Gulf of Aqaba, Egypt, represents a geomorphic province with characteristic land-use (activities) and land-cover (resources). The area has been subject to rapid and increasing changes in land-use pattern, particularly with the growth of tourist activities, construction of new cities, resorts, and the subsequent increase of population. The unplanned changes of land-use have become a major problem where the area is presently suffering from environmental pollution and loss of natural resources. The present study aims at bringing out the temporal changes in land-use/land-cover pattern during the period (1984-2000) and investigating their impact on the ecology and environment of the coastal zone of the Gulf of Aqaba.

Satellite remote sensing plays an important role in providing information about the latest land-use/land-cover pattern in the area and its temporal changes through time. It is the best technology which provides periodical data with high resolution that can be used to detect changes and also evaluate its negative and positive impacts. The information being in digital form can be brought under Geographical Information System (GIS) to provide a suitable platform for data analysis, update and retrieval.

The main objectives of this study are to: (1) delineate major categories of land- use/land-cover to produce a classified map at scale 1: 100,000 covering the coastal plain of the Gulf of Aqaba, (2) detect and evaluate changes in land-use/land-cover brought out by human activities and developments within the period 1984 and 2000. The study revealed that considerable land-use changes have occurred in the area as establishment of protectorates, urban and touristic development and land reclamation.

Accuracy Assessment of Remotely-Sensed Data for Soil Surface Mapping

The North Western Coastal Region (NWCR) of Egypt is one of the most promising areas for agricultural development. It extends 500 km from Alexandria to Sallum in the west, with width of 40 km. The specific objective of the present study was focused to assess the accuracy of the remotely-sensed soil surface maps elaborated by different classification techniques:

  • original data -unsupervised
  • original data -hybrid or semisupervised
  • Principal Component Analysis (PCA) transformed data -hybrid
  • PCA biased transformed data -hybrid

The results indicated that the highest overall accuracy (97.94%) was obtained by PCA biased transformed data -hybnd classification. In contrary, original data -unsupervised classification had the minimum value (73.40 %) to be the poor classification technique. PCA transformed and biased PCA transformed -TM classifications had high accuracy reflected by their mapping performance, but they masked the image infrastructures that can be recovered by filtering process. The higher values of omission and commission errors, calculated by confusion matrix, indicated that the original data -supervised classification has a low potentiality to align spectral classes to informational categories. Categorical accuracy was calculated to express the differential potentiality of the different mapping techniques. When the original data, unsupervised classification, was applied its accuracy had the lower values, especially for mapping sandy soil with abundant shells, rills and ripples (31.45 %). This classification had the higher values of omission and commission errors, to confirm a low mapping potentiality to align spectral classes to informational categories. These accuracy measures can be used to increase the mapping potentiality of the isodata classifications, by assigning the standard deviation of the spectral classes and their distances. The TM mapping indicated that classification errors were not randomly distributed on the image, but they displayed a degree of systematic ordered occurrence in space. Likewise, these errors were not randomly assigned to all the image categories, but were likely to be preferentially associated with certain classes. In addition, the remotely sensed maps indicated that often, erroneously assigned pixels were not spatially isolated but grouped in areas of varied size. These maps revealed an important result that the classification errors have a specific distribution pattern or structural orientation. The misclassified pixels, both omitted and committed, were oriented at the image diagonal of northeast -southwest and its orthogonal of northwest- southeast. This does not certainly mean that the orientation of classification errors must take those but the orientation is associated with the structure of the geomorphological units of the studied area. These orientated errors were more obviously noticed through the spectral classes No.5, 6 and 7 that had omission and commission errors of 54.81 %, 68.55 % and 58.99% respectively. These classes represented the informational categories of sandy soil with abundant shells, rills and ripples; aeolian deposits over limestone and sandy hummocks and ripples.

Pattern and Hazard of Sand Dunes Encroachment with their Environmental Impacts in the New Valley, Egypt

Dunes in the New Valley of the Western Desert of Egypt, move within belts at different rates in a SE-S direction controlled by prevailing wind and local relief (scarps). The southern part of Ghard Abu Muharik in EI-Kharga Depression, the east EI-Farafra dune belt in EI-Dakhla Depression and the Great Sand Sea in Abu Minqar and EI-Farafra Depression are the main locations where sand particularly impinges on settlements, farms, development projects and infrastructures.

An important observation about the natural pattern of the sand dune movements in the Western Desert is that the individual dunes, particularly barchans, commonly move within their belts, but the belts themselves virtually do not shift laterally or advance down the prevailing wind. Besides, the size and shape of these belts are basically unchangeable, reflecting consistency of sand supply from source areas and steadiness of the transport corridors due to virtual absence, so far, of anthropogenic interferences. So, the inter-dune belts (corridors) are evidently much more immune. Previous site selection for some settlements and farms (villages), unfortunately, overlooked this observation. So, villages such as Baghdad and Ganah in El-Kharga Depression suffer considerably from dune encroachment. Their sites were particularly selected for the availability of groundwater along the N-S El-Kharga fault zone. A more appropriate option would have been to build these settlements in the adjacent inter-dune belts and obtain the domestic and irrigation water via pipelines, even if these extend for some kilometers.

Common practices of control of dune movement in the oases involve farm fencing using palm fronds and dune fixation by vegetation. Space images and aerial photographs proved to be indispensable for data acquisition and analysis in the present study. Multi-temporal high resolution imagery (e.g., Ikonos) will add to spatial space-detection of movement of barchan-type (isolated) dunes, but only through elaborate image enhancement and classification.

Impact of Surface Processes and Lithology on Drainage Network Functions and Sustainable Development in South Sinai, Egypt, Using Landsat Images

In South Sinai, there are six cities located on the mouth of the drainage basins at Gulf of Aqaba and Gulf of Suez. Most of these cities are built on alluvial fans, which were deposited by flash floods in Quaternary. Each basin has its own hydrologic characteristics. Geomorphic analysis of these drainage basins and network systems, as well as three-dimension Digital Elevation Model (DEM) are prepared by using Landsat TM image (bands 2, 4 and 7) and calculate the drainage parameters. Field work and profiles in the main target basins were done to study the impact of surface processes and lithology to delineate the localities of hazard, from localities of potentiality and recharge for subsurface water and point the localities which have potentialities for reclamation for agriculture. The surface processes (erosion or deposition) and lithology play great role in the network functions, flash flood and consequently in land-use purposes in South Sinai.

Spectral Reflectance Characteristics of Igneous Rocks in the Visible Region of the Electromagnetic Spectrum

This study was undertaken to provide an experimental basis for geologic interpretation of spectral reflectance of the major rock types in the visible portion of the electromagnetic spectrum, to highlight on the spectral features of the different igneous rock types, according to their mineralogical composition. Rock samples were collected from various types of igneous rocks in Eastern Desert, Egypt, that represent the intrusive and extrusive acidic, intermediate and basic igneous rock groups. The mineralogical analysis of each sample was carried out using XRD technique to identify the essential and minor mineral constituents. The laboratory spectra and spectral curves of the samples show that the transitional metal ions have conspicuous closely-spaced weak bands between 400-500 nm and wide bands between 500- 700 nm. The igneous rocks possess reflectivity between 400-700 nm, with the highest reflective percentage for acidic rocks and the lowest values for the basic ones. The acidic rocks show maximum absorption at 425 nm and their curves increase between 525 and 575 nm without any absorption bands, and increase gradually towards the infrared region. Curves of intermediate rocks are characterized by plateau slopes between 425 and 565 nm with wide space, narrow spectral absorption bands in the red region. The basic rocks possess the lowest reflective values and have the greatest number of absorption bands in blue band and the lowest number at the red band. The principal absorption features result from the presence of biotite, hornblende, muscovite, chlorite, and iron oxide residual in feldspars. The reflectance values of the extrusive rhyolite are less than those of granitic rocks. Color values (RGB) show that the red value is higher than the other color values in acidic rocks, while in intermediate the red and green values are very close. In the basic rocks, values of red and green are nearly equal and higher than the blue value. Accordingly, the red band is the best with respect to the other two bands of the visible light for discrimination of the basement rock types.

Geology and Spectral Characterization of the Basement Rocks at Gabal Gerf Area, Southeastern Egypt

Gabal Gerf area, in southeastern Egypt, is covered by a sequence of Pan-African basement rocks comprising allochthonous ophiolitic rock assemblages thrusted over calc-alkaline metavolcanics and high grade metasediments. These rocks are intruded by syn-to late-tectonic intrusions including gabbro-diorite and tonalite- granodiorite and late tectonic intrusions of layered gabbro and monzogranite, as well as dykes and veins. Sheared metamorphosed ultramafic rocks with the locally pillowed basic metavolcanics are the main components of the Gerf huge ophiolitic nappe complex extending between the N-S Hamisana zone and the Heinai-Allaqi ophiolitic belt. The processed digital data of Landsat ETM ratio images covering the study area have been used. The digital number values (pixel values) and the spectral curves have been delineated for the different encountered basement rocks on both raw ETM and false colour composite (FCC) ratio images. This study revealed that the ETM image bands 7, 4, 2 improves the lithological discrimination of the schistose rocks and massive intrusions, and distinguishes the linear features (dyke swarms and faults). On the other hand, the different basement rocks exposed in the investigated area, particularly the different varieties of the same lithologic unit, can be accurately discriminated using the FCC ratio image (5/7, 5/1,4) in red, green and blue (RGB).

Remote Sensing, Aeroradiometric and Aeromagnetic Interpretation of Wadi Safaga-Wadi Saqia Area, Central Eastern Desert of Egypt

Wadi Safaga -Wadi Saqia area is located in the central Eastern Desert of Egypt, which displays various structural features. The available remote sensing, aeroradiometric and aeromagnetic data were used to deduce the structural lineaments, both on the surface and in the subsurface, as well as to identify the radioactive anomalous zones. The geological, structural and drainage pattern maps of the investigated area were constructed, based on the interpretation of digital multispectral Enhanced Thematic Mapper (ETM+) and panchromatic band-8 acquired from Landsat- 7 satellite. Two main average magnetic interfaces at depths 0.3 and 1 km were calculated through the application of the two- dimensional power spectrum technique. Filtering assisted in the discrimination between shallow and deep sources of magnetic anomalies and produced the residual and regional magnetic component maps. The analysis results of the different magnetic, total count (T.C.) radiometric, drainage pattern and Landsat (ETM+) maps revealed that the area is affected by six tectonic trends, which are arranged according to their magnitude and importance as NW -SE, NE-SW, NNW-SSE, N-S, ENE-WSW and E-W directions. The high radiometric values are observed over the outcropping younger granitic rocks. Meanwhile, the lowest values are associated with the metasediment, metavolcanic and metagabbro rocks. The strongest radioactive anomalies have NW-SE and NE-SW directions, which could be considered valuable as radioactive mineralization zones of economic importance and are considered as significant targets for follow-up and ground investigations.

Application of Airborne Radiometric Data and Landsat-TM Imagery in Exploration for the Mineralization in El-Qasia-Um-Naggat Granites, Central Eastern Desert, Egypt

EI Qasia and Um Naggat granites are relatively small Late-Proterozoic plutons, located north of Idfu-Marsa Alam asphaltic road in the Eastern Desert of Egypt. Ratioing enhancement techniques of Landsat TM images were used for lithological discrimination of different rock types and to distinguish the mineralized from the barren granites in the studied areas. Also, the airborne radiometric data of the same areas were processed to show the distribution and intensities of uranium (U), thorium (Th) and potassium (K40). The color composite images of U, Th, and K40 (in B, G, R) revealed the presence of significant U-anomalies in blue color, confiding with the peripheries of the studied plutons, forming zonal structure. The resulted data were correlated with geological and structural maps prepared by using Landsat TM images, to show the distribution of the mineralized granites. The applied techniques distinguished two granitic types: barren granites occupying the core of both plutons and mineralized granites occurring at the peripheries of these plutons, forming zonal structure. The geochemical studies favored that the barren one is calc-alkaline to alkaline rocks of the I-type, equivalent to G-2 granites and probably were formed by suturing at plate boundaries in compressional environment. The mineralized granites are characterized by relatively higher contents of SiO2, Rb, Zr, Nb, Y, Hf, Ga, U and Th and lesser contents of A12 O3, Fe2O3, Sr, Ba and Zn compared to the barren biotite granites. The high REE content in these granites, and the pronounced negative Eu anomaly in the mineralized granites point to their bearing mineralization. The obtained results demonstrate the suitability of both Landsat TM imagery and airborne radiometric data in exploration for the radioactive-REE bearing granites in the Eastern Desert of Egypt.

Application of CR-39 Solid State Nuclear Track Detectors in Uranium Exploration at Um Ara Area, South Eastern Desert, Egypt

A closed cup technique for radon concentration measurements have been carried out along sixteen trenches located at the northern part of Urn Ara granitic pluton in the south Eastern Desert of Egypt. The measured average values of Rn-222 concentration range between 126.16 ± 24.6 and 393.85 ± 37.85 Bqm-3 while the background values range between 18.47 ± 4.84 and 30.89 ± 10.88 Bqm-3. The values of Rn-222 concentration using α-track are estimated to correspond with the measured values of uranium in the corresponding samples. Using solid-state nuclear track detectors (SSNTDs), it was found that the spatial distribution of Rn-222 along lines traversing the fault and/or joint zones revealed anomalies, clearly connected to the local tectonic structure. The correlation of the radon gas concentration and gamma activity has been plotted with correlation factor of 0.83 and revealed four anomalous zones, where the track counts were more than seven times of background. This study revealed the efficiency of using α-track for uranium prospecting and exploration beside the electronic devices. This new tool can be used as a low-cost technique in uranium exploration as compared to the conventional gamma detection techniques.