ارزيابي آسيب‌پذيري سواحل نسبت به بالا آمدن تراز آب دريا در شهرستان بابلسر

Assessment of Coastal Vulnerability to Sea-Level Rise in Babolsar ownship

پژوهش درباره ي سوانح بزرگ طبيعي و سوانح ناشي از فناوري ها به موضوعي مهم در جغرافيا و كاربرد آن تبديل شده است. امكان تحليل پيچيدگي مسئله در رويكرد سيستمي و در نگاه جامع گراي به جغرافياي نظري و كاربردي و جامع بودن جغرافياي طبيعي و انساني محقق است. با توجه به اينكه نوسانات سطح آب درياي خزر از جمله در منطقه ي ساحلي بابلسر حتي در مقياس دهه اي بسيار سريع اتفاق مي افتد، رعايت عنصر ايمني در سايه ي مديريت يك پارچه ساحلي با تعيين حريم دريا در اين سواحل امكان پذير خواهد بود كه جغرافيا و، به ويژه، ژئومورفولوژي يكي از اركان اصلي در اين نوع از مديريت سواحل است. تعيين حريم نوسانات تراز آب دريا، كه باعث تغييرات مورفولوژيكي در سطح زمين و وارد آمدن خساراتي به تأسيسات انساني مي شود، ضرورت اجراي اين پژوهش را در قالب بررسي نقش شاخص هاي ژئومورفولوژيكي در ساخت و ساز منطقه ساحلي شهرستان بابلسر به خوبي روشن مي سازد. در اين پژوهش، از شاخص آسيب پذيري سواحل (CVI) به منزله ي شاخص ژئومورفيك تأثيرگذار در ساخت و ساز منطقه ي ساحلي بابلسر استفاده شد. ابتدا با استفاده از داده هاي توپوگرافي (مدل رقومي ارتفاع ده متري) و با توجه به نوسانات تراز آب درياي خزر، محدوده ي حايل عمودي اوليه و ثانويه در اراضي شهرستان تعيين شد. محدوده ي حايل عمودي اوليه شامل اراضي است كه در ارتفاع پايين تر از 24.7 متر قرار دارند و محدوده ي حايل عمودي ثانويه اراضي را با ارتفاع بين 24.7 تا 23.5 متر شامل مي شود. در ادامه ي همين بحث و در داخل اراضي محدوده ي حايل عمودي اوليه و ثانويه، شاخص آسيب پذيري ساحل بر مبناي پنج پارامتر ارتفاع، شيب، لندفرم ژئومورفولوژي، كاربري اراضي و فاصله از جاده در دو زير شاخص با منشأ طبيعي و با منشأ انساني اجرا گرديد. با توجه به شاخص آسيب پذيري ساحل بر مبناي متغيرهاي طبيعي (NCVI)، انساني (HCVI) و شاخص آسيب پذيري نهايي (TCVI)، بخش هاي وسيعي از سواحل شهرستان بابلسر (به ويژه در محدوده هاي شهري بابلسر و فريدونكنار) در طبقات با درجه هاي آسيب پذيري بالا و بسيار بالا قرار مي گيرند.

Abstract Coastal areas are dynamic and complex multifunction systems. A wide number of often conflicting human socioeconomic activities occur in these areas. These include urbanization, tourism and recreational activities, industrial production, energy production and delivering, port activities, shipping, and agriculture. Coastal systems are also characterized by important ecological and natural values their high habitat and biological diversity is fundamental to sustain coastal processes and provide ecosystem services which are essential also for human wellbeing. Human activities often conflict with the need to preserve natural coastal systems and their ecological processes. One of the most important applied problems in coastal geology today is determining the physical response of the coastline to sealevel rise. Predicting shoreline retreat and land loss rates is critical to planning future coastal zone management strategies and assessing biological impacts due to habitat changes or destruction. Presently, longterm (>50 years) coastal planning and decisionmaking has been done piecemeal, if at all, for the nations shoreline. Consequently, facilities are being located and entire communities are being developed without adequate consideration of the potential costs of protecting or relocating them from sealevel riserelated erosion, flooding and storm damage. Research on major natural disasters and related technologies has become an important subject in geography and its application. The complexity analysis of the issue is possible in a system approach to theoretical and applied geography also in the integrity of physical and human geography. Due to the Caspian Sea waterlevel fluctuation in coastal zone of Babolsar which happens very quickly in decade scale, the observance of safety element will be possible in light of the integrated coastal zone management with determine of sea frontage. In this context, geography and especially geomorphology is a main basic in this kind of coastal management. Detection of sea level fluctuations causing morphological changes in the earth surface and damage to facilities, clarifies the necessary of the present research to study the role of geomorphological indices in Babolsar coast zone constructions. The Coastal Vulnerability Index (CVI) is one of the most commonly used and simple methods to assess coastal vulnerability to sea level rise, in particular due to erosion and/or inundation. The CVI provides a simple numerical basis for ranking sections of coastline in terms of their potential for change that can be used by managers to identify regions where risks may be relatively high. The CVI results can be displayed on maps to highlight regions where the factors that contribute to shoreline changes may have the greatest potential to contribute to changes to shoreline retreat. In this study, coastal vulnerability index (CVI) is used as effective geomorphic index on Babolsar coast zone constructions. In first, primary and secondary vertical frontages were detect using topographic data (digital elevation model with cell size 10meter) and Caspian Sea waterlevel fluctuations. The primary vertical frontage includes areas which have the lower height of 24.7 meters and secondary vertical frontage consists of areas which are placed between 24.7 and 23.5 meters. Following this issue, within the primary and secondary vertical frontage, coastal vulnerability index was performed based on five parameters, elevation, slope, landform, land use and distance from main road. According to the coastal vulnerability based on natural (NCVI), human (HCVI) and total vulnerability index (TCVI), large parts of the Babolsar coastal zone (especially in Fereidoonkenar and Babolsar city areas) placed in classes of high and very high vulnerability. With respect to detection of the primary (level 24.7 m) and secondary (from level 24.7 to 23.5 m) frontages in Babolsar township area, 345 and 7177 hectares of the township lands are located in the primary and secondary vertical frontages, respectively. The most area of the township land uses in primary frontage belongs to natural structures that have 153 hectares of area. Survey of lands distribution in the height of 24.7 to 23.5 m (secondary vertical frontage) shows that agriculture land use has the most extent in this area the area of this land use is 5293 hectares that equivalent to 74 percent of all lands which are located in the secondary frontage. Urban and industrial structures have 45 and 522 hectares of area in the primary and secondary frontages of Caspian Sea in Babolsar Township, respectively.