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Some Aspects of Sand Stabilization in Egypt
Abstract
Sands and sand dunes occupy vast areas of Egypt. The majority of these areas are of the inland type; the remaining are of the coastal type. The inland dune chains cannot be stabilized by vegetation due to the lack of permanent irrigation in the extremely arid climate, nor by the application of chemicals, which are of prohibitively high cost considering the enormous size of the dune areas involved. Only small sand areas, mostly around shallow wells or in places where the water table comes close to the surface, are stabilized by the growth of natural vegetation.
The stabilization of coastal sand dunes, those where conditions allow stabilization by vegetation, could be carried out through certain steps enacted through a program taking local conditions into consideration. Techniques for the fixation and afforestation of the coastal dunes of Egypt are suggested.
... Stopping dune movement is extremely costly and it is only a practical and economic solution in areas likely to be affected with dune encroachment (Tag El Din, 1986). Sand dune movement risk evaluation is important for countries that have migrating dunes that threaten their towns, transportation routes, or agricultural fields, like the Western Desert of Egypt (Effat et al., 2011). ...
Abstract
This work explores the morphologic characteristics of aeolian dune sand in the southeastern part
of Western Desert of Egypt. It aims to assess the movement of barchan dunes and evaluate their
environmental influence on the Toshka Project. Morphometric investigation of barchan dunes in
the Toshka area revealed that most barchans have high length/width (a/c) ratios (fat to pudgy),
while one-fifth of the studied barchans have lower a/c ratios and so appear normal in their
morphologic forms. Statistical analysis of the main parameters of barchan dunes in Toshka and
other desert regions in the Kharga (Egypt), Kuwait, Southern Morocco, California and Southern
Peru demonstrates that barchans of the Toshka area are distinctive in their appearance. They are
characterized by distinct aspect with higher values of length and width and greater growth in
height. The high-energy wind environment in addition to the large amount of drifting sand are
principal factors responsible for the unique shape of Toshka barchans.
The migration rate of barchan dunes in four chosen test locations, within the central and western
Toshka area, ranges from about 3 to 10.82 m/year. The calculated average migration rate of these
dunes is about 6 m/year in a SSW direction. Sand encroachment is more extensive in the central
and western parts of the investigated Toshka area. Risk evaluation of sand dune movements in
the southeastern part of the Western Desert points to medium to high sand encroachment risk
values. These may represent serious hazards to the newly-established Toshka Project, threatening
roads, as well as cultivated lands in the area.
Egypt (or Misr in Arabic) occupies the north–eastern corner of the African continent. Its eastern territory extends beyond the Isthmus and Gulf of Suez to include the Asian Sinai Peninsula. It lies approximately between latitudes 22° and 32° N, and longitudes 25° and 37° E. It’s longest east to west distance stretches about 1230 km. Egypt is approximately 1100 km at its greatest north to south extent (Embabi, 2018).
Egypt covers an area of approximately 1 million km2 and takes, to a large extent, the form of a square. Egypt is bound by the Mediterranean Sea to the north, the Republic of Sudan to the south, the Republic of Libya to the west, and the Red Sea, the Gulf of Aqaba and Palestine/Israel to the east. The Tropic of Cancer crosses the southern part of the country, positioning Egypt in regions of tropical and subtropical arid climate. Its territory includes the eastern part of the Sahara which forms a part of the great desert belt, which extends from the African Atlantic coast to the west, to the Arabian Peninsula and Iran to the east. Egypt is divided into four geographic regions: the Nile Valley and the Delta; the Western Desert, the Eastern Desert and the Sinai Peninsula. The Nile Valley and the Delta are uniquely situated between the two desert regions. They represent one area of fertile land in the mostly arid North African deserts. The Western Desert is dominated by plateaus, sand dunes and depressions, whereas the Eastern Desert is the region of mountains, which dominate the landscape from north to south. Sinai is a characteristic triangular-shaped region and is bound by bodies of water accompanied by long stretches in all directions.
Sand dunes encroachment is a challenge that faces land development in North African countries. Movement of these dunes threatens cultivated lands, roads, and urban settlements. Geographic information system (GIS) provides a tool for cartographic modeling of risk of sand dunes encroachment. This study modeled the potential risk of sand dunes encroachment related to their terrain characteristics in the Western Desert of Egypt. The Food and Agricultural Organization's land cover map of Egypt derived from Landsat Thematic Mapper was used to locate the sand dunes bodies. Four parameters were derived from Shuttle Radar Topography Mission data, namely the elevation, slope, aspect, and relative moisture index. Ten-year average data for prevalent wind direction and speed were used. A GIS cartographic model was applied using the six parameters as criteria maps. The output is a sand dunes risk index map which was overlaid with the existing urban features. The result identified those urban features vulnerable to sand dunes encroachment risk. The model was verified using a high-resolution image. Such a risk map is essential for land use planning and environmental management.
Wind action is the most dominant agent for erosion and deposition in the vast Western Desert of Egypt. Analysis of wind data
from seven meteorological stations distributed along the Western Desert reveals that this desert is characterized by high-energy
wind environments along the northern and southern edges and low-energy wind environments throughout the rest of the desert.
Accordingly, sand drift potential follows the pattern of wind energy. Maximum sand drift potential was observed at the southern
edge (571 vector units, which equals 40m3/m width/year). Sand drift direction was observed towards the southeast except at the southern part of the desert where the
trend of sand movement was towards southwest. The major dune type recognized on satellite images was the simple linear type.
Linear dunes are generally associated with bimodal wind regime. Rates of sand drift potential and sand dune migration were
greatest at East of Owinate region at the extreme southern part of the desert. Measurements of crescentic sand dune advance
from two satellite images reveal a maximum advance rate of about 9m/year at the southern part of the desert. Dune movement
creates potential hazard to the infrastructures in this open desert.
After a review of the scarce literature on using trees against sand encroachment, a quantitative experiment with a wide shelterbelt to combat sand invasion is reported on. Experimental work was carried out at the northwestern border of the Gezira Scheme (Sudan), an area of severe land degradation and sand movement. Finally, a design of tree shelterbelts for protection against moving sand is discussed. The design suggested from what is known to happen windward of and within shelterbelts and from our experience, is a multi-row, long, wide, tall shelterbelt of low permeability, and with a canopy geometry appropriate for sand protection, without gaps, while its direction should be perpendicular to the prevailing wind. The species selected should have an optimal combination of high growth rate, long life span, high tolerance to existing hazards and byproducts of high economic value.
The Western Desert of Egypt-Its Problems and Potentials
- F El-Baz