تحلیل تاثیر نوسانات دریای خزر بر پایداری خط ساحلی تالاب انزلی

خطوط ساحلی از جمله مناطقی است که تحت تاثیر عوامل مختلف از جمله فعالیت های انسانی و تغییرات تراز دریا، با تغییرات زیادی مواجه بوده است. یکی از سواحلی که با تغییرات زیادی مواجه بوده ، سواحل دریای خزر است. با توجه به اهمیت موضوع، در این تحقیق به بررسی اثرات تغییرات تراز دریای خزر بر تغییرات تالاب انزلی و خط ساحلی پرداخته شد. همچنین از مدل رقومی ارتفاعی 12.5 متر، تصاویر ماهواره لندست و اطلاعات آماری مربوط به تغییرات تراز دریا به عنوان داده های تحقیق استفاده شد. ابزارهای مورد استفاده در تحقیق نیز شامل arcgis، envi و idrisi برای اجرای مدل lcm بود. در این تحقیق، ابتدا تغییرات تراز دریای خزر با استفاده از اطلاعات آماری بررسی شد، سپس با استفاده از تصاویر ماهواره لندست، تغییرات خط ساحلی و تالاب انزلی ارزیابی و در ارتباط با نوسان های دریای خزر تحلیل شد. بر اساس نتایج به دست آمده، در طی سال های 1990 تا 2020، سطح دریای خزر 51 سانتی متر کاهش یافت. همچنین خط ساحلی مورد مطالعه 135.39 متر پسروی داشت و تالاب انزلی نیز با 7.42 کیلومترمربع کاهش وسعت مواجه شد. با توجه به موارد ذکر شده، نوسان های دریای خزر در کنار فعالیت های انسانی از جمله تغییرات کاربری اراضی، از عوامل تاثیرگذار بر خط ساحلی و تالاب انزلی است؛ بنابراین برای هر گونه مدیریت و برنامه ریزی، بایستی پایش مستمر تغییرات دوره ای خط ساحلی نیز قابل توجه قرار گیرد.

Analysis of the Impact of Caspian Sea Fluctuations on the Stability of the Coastline of Anzali Wetland

1 IntroductionDue to the fact that coastlines have a large part of the world #39;s population and many facilities are located along the coasts, shoreline changes can cause a lot of damage to coastal areas. Coastal changes can be caused by natural and human processes and factors; however, coastal processes are often under human activities, locally or globally. Natural processes can also be enhanced or accelerated by human activities. One of the beaches that has undergone many changes is the shores of the Caspian Sea. Fluctuations in the Caspian Sea are faster than other seas and lakes. The Caspian Sea has experienced several periods of extreme fluctuations in recent decades, and this has led to the shifting of the coastline in each period of alteration. The shores of the Caspian Sea have long been of interest to human societies and numerous activities have taken place along its shores. Changes in the water level of this lake have always changed the lives of the inhabitants of the Caspian Sea and have caused damages and in many cases have led to the relocation of settlements and facilities. Also, changes in the level of the Caspian Sea, in addition to the coastline, have had important effects on Anzali Wetland. Due to past fluctuations in the level of the Caspian Sea, this wetland has been affected by these fluctuations more than other coastal areas of the Caspian Sea. Due to the importance of the issue, in this study, the effects of fluctuations in the Caspian Sea level on the coastline and Anzali wetland have been investigated.2 MethodologyIn this study, in order to achieve the desired goals, from 1: 50000 topographic maps, 1: 100000 geological maps, digital model of 12.5 m altitude, Landsat satellite images as well as statistical information related to sea level changes and climate situation Area are used as research data. The instruments used in the research included ArcGIS (in order to prepare the desired maps), ENVI (in order to prepare the desired maps) and IDRISI (in order to analyze the changes that occurred in the coastline and Anzali wetland). Also in this study, LCM models (to analyze land use change information and identify changes in the coastline and Anzali wetland) and a combined model of fuzzy logic and AHP (to identify areas vulnerable to environmental hazards and also identify areas prone to the development of human activities) have been used. This research has been carried out in several stages in accordance with the intended objectives. In the first stage, based on the statistical information of Bandar Anzali metering station, changes in the Caspian Sea level have been evaluated. In the second stage, using Landsat images, the changes of Anzali wetland have been studied. In the third stage, using Landsat images, shoreline changes have been evaluated and in the fourth stage, the relationship between changes in sea level, Anzali Wetland and shoreline has been explored.3 Results In this study, in order to investigate the changes in the Caspian Sea level, information about the leveling station of Bandar Anzali during the years 1990 to 2020 has been used. The results of the evaluation of the changes indicate that the surface of the Caspian Sea has decreased by 51 cm during the study period. Also in this research, using Landsat satellite images, the changes of Anzali wetland have been studied. According to the results, Anzali Wetland has undergone many changes in recent years, to the extent that this wetland in 1990 was about 37.46 square kilometers (wetland water area), which in 1995 increased to 39.24 square kilometers. From this date onwards, the area of the wetland has been decreasing so that the area of the wetland has been reduced in 2000 to 38.59, in 2005 to 37, in 2010 to 35.17, in 2015 to 33.49 and in 2020 to 30.04 square kilometers. The results of the coastline study also indicate that the average shoreline change in the study area from 1990 to 2020 was about 135.4 meters. In fact, during this period of time, under the influence of various natural and human factors, the coastline of the region has experienced a reversal of 135.4 meters.4 Discussion ConclusionsDeclining Caspian Sea level, along with its environmental effects, has caused changes in Anzali Wetland and the coastline. In fact, the declining trend of the Caspian Sea has caused the level of Anzali Wetland to decrease in accordance with this trend and, as a result, the area of the wetland has decreased to the extent that during a period of 30 years, 7.42 square kilometers of wetland area has decreased. This issue has shown a direct effect of sea level decline, although human factors have also played an important role in these changes. Also, the declining trend of the Caspian Sea surface has caused the coastline to regress more rapidly in the study area, so that during a period of 30 years, the coastline of the study area has receded by about 135 meters, part of which is the reason for the decrease in sea level. In addition to sea level changes, human factors have also played an important role in shoreline changes. According to the results, manmade areas have increased by about 20 square kilometers during the years 1990 to 2020; consequently, the increasing trend of population and physical development of Anzali city as well as the development of various infrastructures towards the coastline have caused a change in the coastline and the decline has intensified. Also, human factors have played an important role in the inflow and outflow of water of Anzali wetland, so in changing the size of Anzali wetland these humanrelated factors have also been effective. According to the mentioned cases, the fluctuations of the Caspian Sea along with human activities have been one of the factors affecting the status of the coastline and Anzali wetland.