نوع مقاله : مقاله پژوهشی

نویسندگان

1 مهندسی آب و سازه های هیدرولیکی، دانشگاه آزاد اسلامی، واحد تهران جنوب

2 گروه آموزشی زمین شناسی، دانشگاه خوارزمی، تهران

3 رسوب شناسی، دانشگاه خوارزمی، تهران

چکیده

خطوط ساحلی از مناطقی هستند که حساسیت بالایی در برابر فرسایش و رسوب‏گذاری دارند. خطوط ساحلی همواره مورد توجه کاربری‌‏های انسانی قرار دارند. ولی با توجه به پتانسیل تغییرپذیری بالایی که دارند در معرض مخاطرات هستند. از مخاطرات رایج مناطق ساحلی پس‌روی و پیش‌روی خطوط ساحلی است. با توجه به اهمیت موضوع، در این پژوهش به بررسی تغییرات خطوط ساحلی جنوب استان خوزستان پرداخته شد. در این پژوهش به منظور دستیابی به اهداف مورد نظر از مدل رقومی ارتفاعی 30 متر SRTM، تصاویر ماهواره لندست، نقشه‏های توپوگرافی ۱:۵۰۰۰۰، و نقشه‏های زمین‏شناسی ۱:۱۰۰۰۰۰ به عنوان داده‏های تحقیق استفاده شد. ابزار مورد استفاده Arc GIS‏، ENVI، IDRISI بود. روش کار در این تحقیق به این صورت بود که ابتدا تصاویر ماهواره لندست سال‏های 1990، 2000، 2010، 2020 تهیه و پیش‏پردازش‏های لازم بر آن‌ها انجام گرفت. پس از آن نقشه‏‏های پوشش زمین طی دوره‏های زمانی مورد مطالعه تهیه شد. سپس با استفاده از مدل LCM روند تغییرات خط ساحلی منطقه ارزیابی شد. بر اساس نتایج حاصله، خط ساحلی جنوب خوزستان با تغییرات زیادی مواجه شده است؛ طوری که طی سال‏های 1990 تا 2020 حدود ۷۰۷ کیلومتر مربع از خشکی‏های منطقه مورد مطالعه به پهنه آبی تبدیل شده که عمدتاً مربوط به فرسایش نوارهای ماسه‏ای و همچنین پیش‏روی دریا بوده است. همچنین، در این دوره حدود ۵/۱۴ کیلومتر مربع از پهنه آبی به خشکی تبدیل شده است.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Evaluation of changes in the southern coasts of Khuzestan province Using the LCM model

نویسندگان [English]

  • Mohammad Javad Bahmani 1
  • Khalil Rezaei 2
  • Abdul Reza Hashemi 3

1 Water Engineering and Hydraulic Structures, Islamic Azad University, South Tehran Branch

2 Department of Geology, Khwarazmi University, Tehran

3 Sedimentology, Khwarazmi University, Tehran

چکیده [English]

1-Introduction
The location of shorelines and the state of their changes in the past, present and over time are important for scientists, engineers and managers. For example, analyzing shoreline information for coastal protection design, policy development, updating and reviewing numerical models, assessing sea level rise, developing risk areas for coastal development, achieving the definition of legal property boundary, research and Coastal monitoring is essential. In this article, first the rate of progress and regression of the coastline of southern Khuzestan during the years 1990 to 2020 is examined and then the issue of which part of the coastline of Khuzestan has the most variability is discussed. In this regard, the research hypotheses of variability above the coastline of southern Khuzestan due to the presence of sand masses and most variability of the western parts of the coast of Khuzestan due to the composition of sand masses is the management of coastal areas and implementation Engineering projects in these areas require information such as the current location of the shoreline, its location in the past, and forecasting its location in the future.
 
2-Materials and methods
 Khuzestan province, with 927 km of land border and 975 km of water border, has 136 and 632% of the total land and water borders of the country, respectively (Report of the Geological Survey of Iran, 2016). These figures are equivalent to 635% of the total land and water borders of the country and Khuzestan province is in the sixth place among the border provinces of the country in this regard. The tools used in this study include 1: 50,000 topographic maps, 1: 100,000 geological maps to study the topographic and geological status of the area, the most important of which are Arc GIS, ENVI, IDRISI, SPSS. In this research, achieving the intended goals has been done in several stages, which are described in the following steps. The first stage includes gathering the desired information about the region as well as theoretical foundations on the subject under study. The second stage includes collecting information and layers needed to study the natural state of Khuzestan province. In the third stage, in order to prepare land use maps, Landsat satellite images have been downloaded from the relevant site. After preparing the images, the necessary pre-processing has been done on the images, and finally the land use maps of the area related to the years 1990, 2000, 2010 and 2020 have been prepared. Finally, after preparing land use maps, using the LCM model, the changes made have been studied and analyzed, and using it, the trend of shoreline changes during the study periods has been evaluated.
 
3-Results and discussion
In this study, in order to evaluate the changes in the coastline of the south of Khuzestan province, multi-time satellite images were used. The study of land cover during different periods indicates that the coastlines of Khuzestan province are associated with high variability. In fact, due to the fact that a large part of the coasts of Khuzestan province is covered by low-slope and low-altitude sand strips, these coasts have a high potential for erosion and are affected by the retreat and advance of the sea. The study of the coastline in the study area indicates that the coastline of the south of Khuzestan province is facing a lot of fluctuations and during different periods under the influence of hydro-climatic factors, erosion and sedimentation, has been faced with many changes so that during the year Between 1990 and 2000, much of the coastal sand strip was submerged and actually turned into a blue zone. Most of the changes made during this period were on the southern coast of Bandar emam Khomeini. Between 2000 and 2010, sand strips advanced into the sea and shrinked due to sea retreat and sedimentation. Between 2010 and 2000, it was again faced with the advance of the sea and the increase of the water area, which, like the previous periods, had the most changes in the southern shores of Imam Khomeini port.
 
4- Conclusion
In this study, according to the objectives, the changes of coastlines in the southern coasts of Khuzestan province have been investigated using Landsat satellite images. In this study, first the land cover map related to the years 1990, 2000, 2010 and 2020 was prepared and then the temporal and spatial analysis of changes was performed and then the trend of changes in the coastlines of the study area was evaluated. The results of the evaluation of shoreline changes during the years 1990 to 2020 also indicate that in this 30-year period, due to the fact that the shorelines of the study area are mainly composed of sand strips, it faces many fluctuations and changes. According to the results, during the years 1990 to 2020, about 707 square kilometers of land in the study area has been converted into a water zone, which is mainly related to the erosion of sand belts as well as the advance of the sea. In addition, during this period, 1.6 square kilometers of vegetation and 1.1 square kilometers of man-made areas have been converted into water. Also, the results of the assessment of land cover changes during the years 1990 to 2020 indicate that during this period, about 14.5 square kilometers of water has been converted to land. According to the results, the amount of about 12.3 square kilometers was related to the conversion of water zone to sand zone, the main reason for which is sedimentation and movement of sand masses towards the iodine water zone.

کلیدواژه‌ها [English]

  • Coastal changes
  • LCM model
  • Landsat images
  • Khuzestan coast