جيومورفولوجية الكثبان الرملية وأخطارها بمنخفض الخارجة باستخدام نظم المعلومات الجغرافية والاستشعار عن بعد

جيومورفولوجية الكثبان الرملية وأخطارها بمنخفض الخارجة

باستخدام نظم المعلومات الجغرافية والاستشعار عن بعد

رسالة مقدمة لنيل درجة الدكتوراه في الجغرافيا

من قسم الجغرافيا - كلية الدراسات الإنسانية

جامعة الأزهر - فرع البنات

إعداد الطالبة 

فاطمة عبد الرافع عبد الفتاح محمد أحمد

المدرس المساعد بقسم الجغرافيا

إشراف 

أ.د. آمال إسماعيل شاور

أستاذ الجغرافيا الطبيعية

بكلية الآداب - جامعة القاهرة 

أ.د. عمر محمد الصادق

أستاذ الجغرافيا الاقتصادية

بكلية الدراسات الإنسانية - جامعة الأزهر

  

القاهرة

٢٠١٦ م

Al-Azhar University

Facultyof Human Studies for Girls

Geography Department

Geomorphology of Sand Dunes and its Hazards

in El-Kharga Depression Using GIS & RS

Dissertation Submitted for the Degree of Ph. D. in Geography

Prepared by

Fatma Abd- Elrafea Abd-Elfattah Mohamed

Assistant Lecturer, Geography Department 

Supervised by

Prof. Amal Ismail Shawer

Prof. of Physical Geography

Faculty of Arts, Cairo

Prof. Omar Mohamed Alsadek

Prof. of Economic Geography

Faculty of Humanity Studies 

Cairo

2016

Geomorphology of Sand Dunes and its Hazard in El-Kharga Depression Using Geographic Information Systems and Remote Sensing 

Summary 

    The Study area lies in the southern half of the Western Desert, the depression is bounded by scarps from the east, north and northwest, but it is opened from the south and southwest, the depression lies between latitude 24˚ – 26˚ North, and longitude 30˚ – 31˚ 08 East, this dissertation contains five chapters preceded by a preface and followed by a conclusion.

  The first chapter deals with the physical characteristics of the study area. It is divided into five parts; the first part deals with the geology of the study area. In the second part the relief characteristics is overviewed, through the study of the elevation, slope, aspect, landforms, groundwater and vegetation and their relation to sand dunes. 

  The second chapter studies sand dunes distribution, their types and their morphological characteristics. It has been shown that there are three belts of sand dunes: The western, central and eastern belts. There are also more than one type of sand dunes: Barchans –prevailing type-, Vegetated and obstacle dunes (lee, falling, climbing and echo dunes). Additionally, there are morphological characteristics that showed a strong relation between the dimensions of dunes, as these dimensions in all their stages are growing at the same rate. 

 The third chapter deals with the characteristics of the sand dune sediments. The result of the mechanical analysis shows that the average grain size ranges between 1.96 - 2.76 ᴓ. The other statistical parameters of the grain size as the sorting, skewness and kurtosis show that they are classified as moderately sorted, fine skewed and mesokurtic. The second part of the sand dune sediments analysis is the surface texture of the quartz grains by using scanning electron microscope (SEM). The most frequent features reflect desert environment characteristics as: Upturned plates, dish shaped depressions, horseshoe-shaped depressions, straight and curved scratches, and some features that belongs to sub-aqueous environment. The mineralogical analysis of sand dunes show that they are divided into two groups : opaque minerals and non opaque minerals. There are two sources of sand: the first one is locally represented in the Nubian Sandstone in the area, and the second is from Eastern desert drainage antecedent to the Nile River. 

  Chapter Four studies the dynamics of the erosion and deposition on the surface of barchans. This study comprises the total activity of erosion and deposition along the longitudinal axis of a barchan, and the net change of the erosion and deposition. This change is due to variation in air flow speed, and the curvature of the dune surface. From this study, we can distinguish two zones on the surface of barchans: zone of erosion and zone of deposition. Net changes during the seasons of the year indicate that the maximum erosion prevails in spring, while the minimum prevails in autumn. However, the winter is the only season which is characterized by net change of deposition. There is strong correlation between the net change and dune migration, where net change on the barchan surface tend to erosion, the migration of dune increases. 

  Chapter Five studies the movement of sand dunes and their hazards. Studying movement of sand dunes show that their annual movement ranges between 2.9 – 18.3 m/y. The drift potential attains its minimum in January and its maximum in May. By monitoring the hazards that result from dune movement, it was found that sand encroached many areas of cultivated land, some sections of the roads and settlements. At the end of this chapter, the study introduces some suggestions to living with the dunes at the least of risks. 

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