پیش‌بینی مقدار تغییرات سالانۀ خط ساحلی دریای خزر (محدودۀ دلتای رودخانه‌ای گرگان‌رود)

نوع مقاله : مقاله کامل

نویسنده

استادیار دانشکدة علوم انسانی و اجتماعی، دانشگاه مازندران

چکیده

امواج، جریان‌های دریایی و باد تحت تأثیر نوسان‌های سطح آب دریا، تغییرات زیادی بر مناطق ساحلی تحمیل می‌کند. در این پژوهش، پیش‌آمدگی دلتای رودخانه‌ای گرگا‌ن‌رود در مصب بررسی شده است. هدف این تحقیق، بررسی مقدار تغییرات خط ساحلی با استفاده از دو روش مختلف و پیش‌بینی موقعیت آیندة این خط است. با تهیه و پردازش تصاویر ماهواره‌ای در نرم‌افزار ENVI و رقومی‌سازی آنها در نرم‌افزار ARCGIS9.3، بررسی مقدار تغییرات و پیش‌بینی آیندة موقعیت خط ساحلی با استفاده از روش برش‌های عرضی ارزیابی شد. با توجه به طول پیش‌آمدگی دلتا در داخل دریای خزر و مقدار تغییر متوسط سالانة 2/40 متر به روش مقدار نقطة پایانی، پیش‌آمدگی قاعدة دلتای گرگان‌رود به داخل دریا طی 112 سال اخیر شکل گرفته است. نتایج نشان می‌دهد مقدار متوسط تغییرات سالانه در محدودة بررسی‌شده با روش نقطة پایانی و مقدار میانگین، به‌ترتیب معادل2/40 و 1/61 متر در سال است. در بین دو روش استفاده‌شده، روش مقدار نقطة پایانی برای پیش‌بینی تغییرات دوره‌های کوتاه‌مدت و روش مقدار میانگین برای پیش‌بینی تغییرات دوره‌های بلندمدت کارایی بهتری دارد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The Prediction of Annual Rate of Shoreline Change in the Caspian Sea, Gorganroud River Delta

نویسنده [English]

  • Ghasem Lorestani
Assistant Professor, Faculty of Humanities, University of Mazandaran, Mazandaran, Iran
چکیده [English]

Introduction
The coastal zone is one of the greatest environmental and economic assets of each nation. In coastal regions the natural forces that cause shoreline changes are embodied in waves, currents, wind and other factors. Gorganroud River Delta is located in 53°57 to 54° 1 E and 36°56 to 37° N in Southeast part of Caspian Sea. In this study, gibbosity of Gorgan River delta has been studied at the river mouth. The Gorganroud River basin from the Caspian Sea catchment basin is covering a large part of it in Golestan Province. The total flow rate of Gorgan Bay River Catchment is about 500 cubic meters and total of their discharge is 3.5 million tons per year. With average slope less than 0.1 percent, the study area is very low slope.
 
Material and Methods
The aim of this study is to evaluate the rate of change in coastline and its predictions with two different methods. The reason of selection of Gorganroud coastline is a very large amount of change over different periods of time. This research is mainly based on an analytical method using mathematical and statistical tests. Topographic maps 1:250000 and 1:50000 of the study area have been used for the analysis. Initially, the satellite images of TM, MSS, and ETM sensors were obtained from Landsat and the images of the coastline in 2005 and 2013 were extracted from Google Earth. The shorelines were extracted by digitization of the images and converted into linear files in ARCGIS 9.3. To investigate the rate of annual change in the coastline, two methods have been applied. The methods used to evaluate the rate of annual change in shoreline and to predict the rate of change in the next years was based on the use of transect. According to the curved coastline, the cuts perpendicular to the coastline are at even intervals of 500 meters. This is to analyze the rate of change within Gorgan River Delta. The first method used is End Point Rate (EPR). The End Point Rate is calculated by dividing the distance of shoreline movement by the time elapsed between the oldest and the most recent shoreline. The major advantages of the EPR are the ease of computation and minimal requirement of only two shoreline dates. The major disadvantage is that in cases where more data are available, the additional information is ignored. The second method to predict the rate of changes is The Average of Rates (AOR). The Average of Rates method calculates separate end point rates for all combinations of shorelines when more than two are available. A minimum time criterion is introduced to filter the available shorelines and it is a function of measurement errors and the magnitude of the rate of change. The main advantages of this method are that all “good” data that pass the minimum time criterion are used and the method is sensitive to substantial shifts in trends and data variability. The main disadvantages are that small time differences between the shorelines produce a long minimum time span and there is not a computational norm for modeling of the minimum time span equation.
 
Results and Discussion
The results of the EPR method show that most of the changes in the coastline are in the middle of Gorganrood river delta. The changes are ranged from 63.7 to 84.2 meters per year. Minimum changes by EPR method is ranged from 18.6 to 12.9 meters per year in the southern part of the study area. In the entire study area, Average annual changes by the EPR method is 40.2 meters. The minimum changes by AOR method is between 32 to 35.7 meters per year in the southern part. The maximum changes by this method are ranged from 60.4 to 90.8 meters per year. Average changes in AOR method is equivalent to 61.1 meters per year.
 
Conclusion
Since 1882, according to the measurement data of sea-level stations in Baku and Anzali, changes in water level are more than 3 meters. These changes had a significant impact on coastline profile and its surrounding landuses. Evaluation methods used implies that EPR and AOR methods are considered as cyclical changes. According to the Delta jut into the sea and annual average rate of change of 40.2 meters, with EPR method, gibbosity Gorganroud River at the mouth of the river have been added to the coastline in the past 112 years.

کلیدواژه‌ها [English]

  • changes rate
  • coastline
  • Gorganroud River
  • prediction transect
  1. آزرم‌سا، ع. و رزمخواه، ف. (1385). «بررسی موقعیت خط ساحلی در خلیج چابهار با استفاده از داده‌های ماهواره‌ای». علوم زمین. س 15. ش 60. ص 25-32.
  2. ـــــــــــ و رزمخواه، ف. (1389). «پیش‌بینی موقعیت و نحوة تغییرات خط ساحلی در خلیج پزم تا سال 2010». فیزیک زمین و دریا. دورة 36. ش 4. ص 89-98.
  3. افشین. ی. (1373). رودخانه‌های ایران. ج 2. تهران: وزارت‌نیرو. شرکت مهندسین مشاور جاماب.
  4. خوش‌رفتار، ر. (1384). «تکامل ژئومورفولوژیکی دلتای سفیدرود». رسالة دکتری ژئومورفولوژی. به‌راهنمایی جمشید جداری عیوضی. تهران: دانشگاه تهران. دانشکدة جغرافیا.
  5. جعفر‌بیگلو، م.، زمان‌زاده، م.، یمانی، م. و عمادالدین، س. (1391). «شواهد ژئومورفولوژیک تغییرات سطح اساس دریای خزر طی کواترنر پسین در محدودة رودخانة گرگان‌رود». پژوهش‌های جغرافیای طبیعی، س 44. ش 2. ص 33-50.
  6. رابینو، ی. (1389). مازندران و استرآباد. ترجمة غلامعلی وحید مازندرانی. چ 5. تهران: انتشارات علمی فرهنگی.
  7. لاهیجانی، ح. توکلی، و. و امینی، ع. (1386). «مورفولوژی دهانة رودخانه‌های جنوب خزر در شرایط اثر عوامل انسانی و تراز آب». علوم محیطی، س 5. ش 2. زمستان 1386. ص 45-55.
  8. لاهیجانی، ح. حایری اردکانی، ا.، شریفی، ا. و نادری‌بنی، ع. (1389). «شاخص‌های رسوب‌شناختی و ژئوشیمیایی رسوبات خلیج گرگان». اقیانوس‌شناسی، س 1. ش 1. بهار 1389. ص 65-86.
  9. یمانی، م.، مقیمی، ا.، معتمد، ا.، جعفربیگلو، م. و لرستانی، ق. (1392). «بررسی تغییرات سریع خط ساحلی به روش تحلیل نیمرخ‌های متساوی‌البعد». پژوهش‌های جغرافیای طبیعی. س 45. ش 2. ص 1-20.
  10. برد، ا. (1392). ژئومورفولوژی ساحلی. ترجمة مجتبی یمانی و وحید محمدنژاد. تهران: مؤسسه انتشارات دانشگاه تهران.
    1. Appeaningaddo, K., Walkden, M. and Millsa, J.P. (2008). "Detection, measurement and prediction of shoreline recession in Accra, Ghana". Photogrammetry & Remote Sensing 63 (2008). pp. 543–558.
    2. Afshin, Y. (1994). Rivers of Iran. Vol. 2. Tehran: Ministry of Energy. JAMAB. (In Persian).
    3. AzarmSa, A. And Razmkhah, F. (2006). "Study of Coastline Position in Chabahar Bay Using Satellite Data, Earth Sciences". Fifteenth year. No. 60. pp. 32-25. (In Persian).
    4. AzarmSa, A. And Razmkhah, F. (2010). "Determination of Shoreline Position in Pozm Bay Using Landsat Satellite Data". Physics of the earth and sea. Vol. 36. No. 4. pp. 98-89. (In Persian).
    5. Bamasoud, A. and Louisebyrne. L. (2013). "The predictive accuracy of shoreline change rate methods in Point Pelee, Canada". Journal of Great Lakes Research 39 (2013). pp. 173–181.
    6. Bird, E. (2013). Coastal geomorphology. Translate by Mojtaba Yamani and Vahid Mohammad-nejad. Tehran: University of Tehran Press. (In Persian).
    7. Crowell, M., Douglas, B.C. and Leatherman, S.P. (1997). "On forecasting future U.S. shoreline positions: a test of algorithms". Journal of Coastal Research. 13(4). pp. 1245–1255.
    8.  Crowell, M., Honeycutt, M. and Hatheway, D. (1999). "Coastal erosion hazards study: phase one mapping". Journal of Coastal Research. Special Issue No. 28. pp. 10–20.
    9. Dolan, R., Fenster, M.S., and Holme, S.J. (1991). "Temporal analysis of shoreline recession and accretion". Journal of Coastal Research. 7(3). pp. 723–744.
    10. Doukakis, E. (2007). "Using Quality Metrics to Choose Shoreline Change Estimation Methodology". Abstracts of EcoSummit 2007 Ecological Complexity and Sustainability Challenges & Opportunities for 21st Century's Ecology.
    11. Fenster, M.S., Dolan, R. and Elder, J.F. (1993). "A new method for predicting shoreline positions from historical data". Journal of Coastal Research. (1). pp. 147–171.
    12. Foster, E.R. and Savage, R.J. (1989). Methods of historical shoreline analysis. In: Coastal Zone ’89. New York: American Society of Civil Engineers. pp. 4434–4448.
    13. Genz, A.S., Fletcher, C.H., Dun,. R.A., Neilfrazer, L. and Rooney, J.J. (2007). "The Predictive Accuracy of Shoreline Change Rate Methods and Alongshore Beach Variation on Maui, Hawaii". Journal of Coastal Research. January 2007. pp. 87–105.
    14. Iranian National Center for Oceanography (INCO) (1998). "TSS-1 Technical Report. Iranian National Center for Oceanography". IR Iran.
    15. Jafar-Beglou, M., Zaman-zadeh, M.H. Yamani, M. and Emad-al-din, S. (2012). "The Geomorphological Evidence of the Caspian Sea Base Level Changes during the Late Quaternary in the Confine of Gorgan-roud River". Research in Geography, Year 44. No. 2. pp. 33-50. (In Persian).
    16. Kakroodi, A.A., Kroonenberg, S.B., Mohamah-Khani, H., Yamani, M., Hgasemi, M.R and Lahijani, H.A.K. (2012). "Rapid Holocene Sea-level Changes along the Iranian CaspianCoast". Quaternary International. Vol. 263. pp. 93-103.
    17. Khosh-raftar, R. (2005). "Geomorphological evolution Sefidrud Delta". Geomorphology Ph.D. Dissertation. Supervisor of Jamshid Jedari-ayvazi. Tehran: University of Tehran. Department of Geography. (In Persian).
    18. Lahijani, H.A.K., Tavakoli, V. and Amini, A. (2008). "South Caspian River Mouth Configuration Under Human Impact and Sea level Fluctuations". Enviromental Sciences. Vol. 5. No. 2. Winter 2008. pp. 65-86. (In Persian).
    19. Lahijani, H.A.K., Rahim-pour-Bonab, H., Tavakoli, V. and Hosseindoost, M. (2009). "Evidence for Late Holocene High Stands in Central Guilan-East Mazanderan, South Caspian Coast, Iran". Quaternary International. No. 197. pp. 55-71.
    20. Lahijani, H., Haeri-Ardekani, O., Sharifi, A. and Naderi-Bani, A. (2010). "Gorgan Bay sediment deposition and geochemical indicators of cognitive". Oceanography. year 1. No. 1. Spring 2010. pp. 45-55.
    21. McBride, R.A., Penland, S., Hiland, M.W., Williams, S.J., Weasphal, K.A., Jaffe, B.E. and Sallenger, A.H. (1989). "Analysis of Barrier Shoreline Change in Louisiana from 1853 to 1989". Louisiana Barrier Island Erosion Study. Atlas of Shoreline Changes I- 2150- A.
    22. Mukhopadhyay, A., Mukherjee, S., Mukherjee, S., Ghosh, S., Hazra, S. and Mitra, D. (2012). "Automatic shoreline detection and future prediction: A case study on Puri Coast, Bay of Bengal, India". European Journal of Remote Sensing- 2012. 45. pp. 201-213.
    23. Pethick, J. (1991). An introduction to coastal geomorphology. Routledge. Chapman and Hall. Inc. Fifth impression.
    24. 34.  Rabinio, Y.L. (2010). Mazandaran and Astarabad. Translated by Gholam-ali. Vahid-mazandarani. Fifth Edition. Tehran: Scientific and Cultural Publications. (In Persian).
    25. Wesswling, F and et al. (2002). "Establishing Holocene sea level in the Caspian Sea using combined molluscan bathymetry and isotope geochemistry". Now Workshop Holocene Caspian Sea Level Change. 21-22 october.
    26. Yamani, M., Moghimi, E., Motamed, A., Jafarbeglo, M. and Lorestani, Gh. (2013). "Fast Shoreline Changes in Sefidrud Delta Using Transects Analyses Method". Research in Geography. Year 45. No. 2. pp. 1-20. (In Persian).