پراکنش توزیع تپه های ماسه ای بزرگ در زمان حاضر عموماً وضعیت ثابتی دارند . (نسبت به تپه های کوچکتر از حرکت کمتری برخوردارند).و نشان می دهد که در دوره وورم توزیع سیستمهای فشار اتمسفری و جهت وزش بادها مشابه زمان کنونی بوده اما بطور قابل توجهی از شدت بیشتری برخوردار بوده است .
اين دانشجوي مديريت مناطق بياباني خاطر نشان كرد : براساس طرح ارائه شده وضعيت فعلي و مهمترين عوامل موثر در بيابان زايي مناطق جنوبي فارس محاسبه ميشود و با امتياز دهي به پارامترهاي موثر در بيابان زايي و با استفاده از سامانه اطلاعات جغرافيايي، نقشه شدت بيابان زايي محاسبه و تدوين مي شود.
سپهر ادامه داد: اين مدل با توجه به شرايط منطقهيي تنظيم شده است اما قابليت تعميم به ديگر مناطق كشور را نيز دارد.
دكتر عليمراد حسنلي، استاد بخش مديريت مناطق بياباني دانشكده كشاورزي دانشگاه شيراز و استاد راهنماي اين پاياننامه نيز درگفتوگو با ايسنا توضيح داد: اين مدل براساس مدل اروپايي مدالوس براي مناطق خنج لارستان در فارس اصلاح و ارائه شده است.
وي با بيان اينكه اين مدل قابليت تغيير براي ديگر مناطق بياباني ايران نيز دارد يادآور شد: براي اين مدل 40 هكتار از اراضي بياباني لارستان مورد مطالعه قرار گرفته است و براساس داده هاي اقليمي، تنوع آب، خاك و گياهان و فرسايش ميزان شدت بياباني زايي محاسبه مي شود.
اين استاد دانشگاه شيراز خاطر نشان كرد: اين مدل كيفي است و علاقمنديم مدل رياضي آن تدوين شود و هر چند كه يك گام ساسي براي مبارزه با بيابانهاي جنوب با ارائه اين مدل برداشته است اما نياز به كارهاي اساسي و تحقيقات كاربردي بيشتر در آينده دارد.
گفتني است، اين طرح با همكاري دانشگاه شيراز، پژوهشكده مناطق خشك و بياباني دانشگاه يزد و سازمان هواشناسي ايران تهيه و ارائه شده است.
منبع: ایسنا
Wind erosion, unlike water, cannot be divided into such distinct types. Occurring mostly in flat, dry areas and moist sandy soils along bodies of water, wind erosion removes soil and natural vegetation, and causes dryness and deterioration of soil structure. Surface texture is the best key to wind erosion hazard potential. All mucks, sands, and loamy sands can easily be detached and blown away by the wind, and thus are rated a severe hazard. Sandy loams are also vulnerable to wind, but are not as susceptible to severe wind erosion as the previously mentioned soils. Regular loams, silt loams, and clay loams, and clays are not damaged by the wind, but on wide level plains, there may be a loss of fine silts, clays, and some organic matter.
 Wind erosion is a serious problem in many parts of the world. It is worse in arid and semiarid regions. Areas most susceptible to wind erosion on agricultural land include much of North Africa and the Near East; parts of southern central, and eastern Asia; the Siberian Plains; Australia; northwest China; southern South America; and North America. |
  Wind erosion is a major problem on about 75 million acres of land in the United States. About 5 million acres are moderately to severely damaged each year. Wind erosion physically removes from the field the most fertile portion of the soil. Some soil from damaged land  enters suspension and becomes  part of the atmospheric dust load. Dust obscures visibility and pollutes the air and water, causes automobile accidents, fouls machinery, and imperils animal and human health. |
Wind erosion is a serious environmental problem attracting the attention of many across the globe. It is a common phenomenon occurring mostly in flat, bare areas; dry, sandy soils; or anywhere the soil is loose, dry, and finely granulated. Wind erosion damages land and natural vegetation by removing soil from one place and depositing it in another. It causes soil loss, dryness and deterioration of soil structure, nutrient and productivity losses and air pollution. Suspended dust and dirt is inevitably deposited over everything. It blows on and inside homes, covers roads and highways, and smothers crops. Sediment transport and deposition are significant factors in the geological changes which occur on the land around us and over long periods of time are important in the soil formation process.
Soil movement is initiated as a result of wind forces exerted against the surface of the ground. For each specific soil type and surface condition there is a minimum velocity required to move soil particles. This is called the threshold velocity. Once this velocity is reached, the quantity of soil moved is dependent upon the particle size, the cloddiness of particles, and wind velocity itself.
Suspension, saltation, and surface creep are the three types of soil movement which occur during wind erosion. While soil can be blown away at virtually any height, the majority (over 93%) of soil movement takes place at or below one meter.
Suspension occurs when very fine dirt and dust particles are lifted into the wind. They can be thrown into the air through impact with other particles or by the wind itself. Once in the atmosphere, these particles can be carried very high and be transported over extremely long distances. Soil moved by suspension is the most spectacular and easiest to recognize of the three forms of movement.
Saltation - The major fraction of soil moved by the wind is through the process of saltation. In saltation, fine soil particles are lifted into the air by the wind and drift horizontally across the surface increasing in velocity as they go. Soil particles moved in this process of saltation can cause severe damage to the soil surface and vegetation. They travel approximately four times longer in distance than in height. When they strike the surface again they either rebound back into the air or knock other particles into the air.
Creep - The large particles which are too heavy to be lifted into the air are moved through a process called surface creep. In this process, the particles are rolled across the surface after coming into contact with the soil particles in saltation.
Surface texture is the best key to wind erosion protection. Properly managed crop residues, carefully timed soil tillage, and accurately placed crop strips and crop barriers can all effectively reduce wind erosion.
Strategy 1
Improve wind erosion prediction technology for cropland and extend it to range and disturbed land
Wind erosion prediction technology is applied to many problems: assessment of erosion control systems; determining national trends in erosion from various land uses; and simulating erosion for off-site environmental impact studies. New, physically based, wind erosion prediction technology will improve erosion predictions and the design of erosion control systems
Goals:
-Develop a process-based Wind Erosion Prediction System (WEPS) that includes capability to simulate weather, the field soil and crop conditions, and wind erosion on a daily basis.
-Develop databases needed to support WEPS on a national basis
-Develop capabilities of WEPS to predict suspended dust, including fine particulates (PM-10) and plant damage
- Develop additional submodels that extend WEPS to range and distributed lands
Strategy 2
Increase our understanding of wind erosion processes to provide a scientific basis for development of prediction technology and of control measures
The processes that control wind erosion involve a multitude of interactions between climate, soil, plants, and management. A better understanding of the processes involved will provide scientific methods to improve the prediction and control of wind erosion. The application of these technologies will improve and maintain the quality of the world's soil, air, and water resources; reduce damage to plants and machinery; improve the health of animals and humans; and reduce costs to society.
Goal:
- Conduct basic research on wind erosion processes to improve prediction technology
Strategy 3
Determine the on-site and off-site consequences of wind erosion
Conservation planning, economics, policies, and decisions often are based on the perceived consequences of wind erosion. However, information is inadequate about the on-site and off-site consequences of wind erosion. The state of knowledge is better for the on-site than for off-site consequences. However, the process-based Wind Erosion Prediction System will provide users with simulation capabilities that were not available in previous wind erosion prediction tools. Hence, it will improve our evaluation of both off-site and on-site problems
Goals:
-Determine effects of wind erosion on soil quality and productivity to enable simulation and evaluation of economic costs.
Quantify the effects of plant abrasion, burial, and blowouts by wind erosion-
Develop criteria for evaluating acceptable levels of wind erosion-
-Quantify the impacts of off-site consequences of air-borne sediments and attached chemicals on visibility, air quality, human health, water quality, economic costs (cleanup & machinery), habitat quality, and atmospheric albedo
Strategy 4
Develop economically and environmentally viable practices, guidelines, and systems that customers can apply to control wind erosion
For owners and managers to reduce susceptibility of their land to wind erosion and mitigate its effects when it does occur, they must be able to successfully implement current and future control practices that are economically and environmentally viable. New knowledge obtained from basic wind erosion-related research is utilized to produce innovative and improved practices, guidelines, and systems for application by end users. For users to employ these strategies, the information must be disseminated in a manner they comprehend. This requires information on potential economic and environmental impacts
Goals:
-Experimentally evaluate various soil- and climate-specific tillage and residue management practices for reducing wind erosion
-Enable customers to use WEPS directly in a decision aid mode to evaluate various combinations of control practices and determine the most cost-efficient practices for achieving the desired level of control
Strategy 5
Provide customer satisfaction through effective technology transfer
The Wind Erosion Research Unit conducts research of importance to society. The technology resulting from this research aids customers in understanding, predicting, and controlling wind erosion. To enjoy this benefit, technology must be transferred effectively to the customer
Goals:
Develop an international network for cooperation and information exchange-
-Provide user friendly training manuals for the use and interpretation of control strategies and WEPS technology.
Develop an educational version of WEPS and appropriate educational materials-
-Participate in joint field demonstration/research projects with the Natural Resources Conservation Service and extension agencies showing the benefits of wind strips, surface roughness, and standing and flat residues on reducing wind erosion.
-Sponsor an international symposium in 1997 celebrating the 50th anniversary of the Wind Erosion Research Unit
-Assist the Natural Resources Conservation Service (NRCS) in implementing WEPS into the Field Office Computing System (FOCS)