9Sand Dune Stabilization Temporary Sand Control SystemsSand ShieldingSand FencesPermanent Sand Control SystemsAfforestation
10Sand Shielding Stone Mulch Water or Brines Wetting Chemical StabilizersBiological Crusting
11Stone MulchGravel, stone or crushed rock blankets are used as mulches.Blankets formed of gravel smaller than ½ in. in diameter can withstand wind velocities up to 137 km/hr.A 1-in. layer of aggregate or gravel is normally adequate for areas not subject to traffic.Suggested grading:Passing 1 ½ in. sieve 100%Passing 1 in. sieve %Passing ¼ in. sieve %
12Water, Wastewater or Brine Wetting Increases cohesion between grains.Increases in the percentage of the fines (silt and clay) particles between the sand grains.Grow vegetations existing in the area.Reduce the harmful salt content in the soil.Brines rich in carbonates or sulfates precipitate salts that tend to cement the sand grains and resist wind erosion.
13Chemical StabilizersThe nature of the bonding by chemical stabilizers in sand is adhesive.Some other chemicals form a film on the sand grains that increases its specific gravity and consequently decrease the rate of erosion.
14Effectiveness of a Chemical as a Stabilizer Its solubility in waterOptimum dilution ratioOptimum application rateBonding strengthRate of surface erosionEffective life of the chemical under field conditions (heat, humidity, rain and ultraviolet rays).Effect of the chemical on seed germination and plant growth
15A good bonding action of a chemical stabilizer between sand grains.
16A weak but permeable bonding action of a chemical stabilizer between sand grains
17Biological CrustingDewfall is a process whereby moisture from the atmosphere condenses on the earth’s surfaceThe frequent occurrence of dew can serve as an important source of moisture for biological crustsThe crust is formed by biological activity of blue-algea.This idea is worth further investigations under the Saudi Arabian climatic conditions.
19Checkerboard Fences Constructed of plant remains or plastic nets 50-70 cm high forming 3 x 3 m rectanglesCan withstand weather conditions for few years, which is long enough to implement the permanent solution
20Impounding Sand Fences Fence heights should range between 0.5 m to 1.2 mFences should be erected around 50 m down-wind the erosional area or times the fence height from the area to be protectedMultiple rows of fences can trap more than 80% of wind-borne sandGaps should be left between long fences to lessen the load caused by wind and accumulated sandThe porosity of the fence should range between 30 and 40%A fence should extend times its height beyond the area to be protected
21Impounding Sand Fences (continued) Since the fences will eventually be buried by trapped sand, new fences must be erected on the accumulating moundFences should be located in areas where the creation of a large artificial dune will not pose any problems
22Impounding Sand Fences (continued) Fences will require regular maintenance and renewal to avoid deterioration or constructed from better material
23Diversion Sand FencesThey are erected either as single fences slanted at about 45o from the wind direction or in the form of a V-shaped fences pointing up-windThey not only trap the sand but also deflects it away from the area that needs to be protectedThe effectiveness and life span of the diversion fences depends on the material of construction, height and porosity
24Permanent Sand Control System (Afforestation) Decrease the wind speedProtect the ground from scouringChange the microclimate in the areaEnhance the soil condition for further plant growthCreate recreational areasAn appealing way to mitigate the dune migration hazard
26Water The presence of water is vital for plant growth Rain is scarce in desert areasOther sources of water should be envisagedGroundwater resources, rain and dew water harvesting and wastewater are posibilitiesAlso water harvesting from sabkha should be considered
27Plants Quantity and quality of the available water Soil moisture contentPercentage of salts in the soilSpeed and direction of windRate of sand movementRate of plant growthCapability of the plant to multiplyCapability of the plant to enhance the soil conditionThe root system of the plant
28Site MaintenanceThe site should be protected against possible unlawful grazing activitiesThe site should be protected against possible trespassing and firewood cutting
29Stabilization Programs in Arid Countries (Case Histories) The stabilization programs used in China, Pakistan, Iran, UAE, Kenya, Libya, Palestine, USA and Saudi Arabia were reviewedThe most effective and permanent mean of sand dune stabilization is the afforestationTamarix, Acacia and Calligonum have been successfully used to stabilize dunes in many countriesPrior to vegetation a temporary sand stabilization using ground shielding was always necessary
30Suggested Sand Control Plan for the Eastern Region The plan is based on the previous knowledge of the geology and geomorphology of the regionThe region is mainly covered by sand dunes (barchans, shield or parabolic) and sand sheetsThe sand bodies are locally underlain by sabkha soilLimestone outcrops form the highlands in the areaSeveral limestone quarries producing aggregates are present around Dhahran-Dammam area
31Elements of the Suggested Sand Control Plan in a Test Plot Temporary stabilization using stone mulchPermanent stabilization using vegetationWater harvesting
32Temporary Stabilization Using Stone Mulch Crushed limestone is suggested to be used as stone mulch to cover the windward face of several barchan dunes in a limited selected dune fieldThe specification of the US Highway Research Board for stone mulching can be implemented in this test
33Permanent Stabilization Using Vegetation Drought resistant plants such as Parkinsonia aculeate, Prosopis juliflora, Atriplex spp., Tamarix aphylla and/or Tamarix nitotica were recommendedThe experience of the Research Institute of King Fahd University of Petroleum and Minerals in this aspect should be considered
34Freshwater Harvesting from Sabkha Brines Solar stills were used to harvest fresh water from the brines of Al-Lith sabkhaEach solar still covered 10 m2 of sabkha area
35Freshwater Harvesting (continued) Freshwater was produced on the average of 1.2 to 1.8 lit/day/m2This amount can be improved by some modifications to the solar still