کاربرد مدل شاخص آسیب‌پذیری تپه‌های ماسه‌ای (dvi) در ارزیابی تپه‌های ماسه‌ای ساحلی از بندر سیریک تا بندر زیارت در جنوب‌شرق استان هرمزگان

تپه‏های ماسه‏ای مانعی در برابر امواج‏اند و می‏توانند سواحل را از فرسایش حفظ کنند. بنابراین، حفاظت از این تپه‏ها امری مهم و نیازمند مدیریت است. هدف از این پژوهش بررسی میزان آسیب‏پذیری تپه‏های ماسه‏‏ای واقع در حد فاصل بندر سیریک تا بندر زیارت در جنوب ‏شرق استان هرمزگان است، زیرا ساخت اسکله‏های جدید در سال‏های اخیر به تغییراتی در ساحل این منطقه منجر شده است. بنابراین، آگاهی از وضعیت آسیب‏پذیری تپه‏های ساحلی می‏تواند در مدیریت و حفاظت این تپه‏ها اثربخش باشد. در این پژوهش، عوامل موثر در آسیب‏پذیری تپه‏های ماسه‏ای ساحلی، شامل شرایط ژئومورفولوژی تپه‏های ماسه‏ای، عوامل دریایی، فرایندهای بادی، پوشش گیاهی، تاثیر فعالیت‏های انسانی، و عامل مدیریتی، با استفاده از چک‏لیست، ارزیابی شد. داده‏های استفاده‏شده شامل داده‏های آماری، داده‏های مکانی، بازدیدهای میدانی، تصاویر ماهواره‏ای، عکس‏ هوایی، و نتایج گرانومتری است. نتایج نشان داد میزان شاخص آسیب‏پذیری (dvi) در همه محوطه‏ها متوسط است. همچنین، مشخص شد در میان عوامل مورد بررسی، عامل وضعیت ژئومورفولوژیک تپه‏های ماسه‏ای و سپس فرایندهای بادی به‏ترتیب بیشترین تاثیر را در آسیب‏پذیری تپه‏ها دارند. ارزیابی شاخص تعادل نشان داد تعادل میان آسیب‏پذیری و مدیریت تپه‏ها در هیچ کدام از محوطه‏ها وجود ندارد که دلیل آن می‏تواند نبود متولی مشخصی در زمینه مدیریت اجرایی حفاظت از سواحل باشد.

Application of dune vulnerability index (DVI), in evaluation coastal dunes, from sirik port to Ziarat port in southeastern of Hormozgan

Introduction: Coastal sand dunes are one of the important morphological forms of coastal areas that form behind the coast. These hills have been caused by interactions of sea waves, sea currents, winds and sediment materials on the coast. Sand dunes can protect the coast against waves and erosion, so protecting these hills is important and requires management. Study area is located between the Sirik port and the port of Ziarat, in the southeast of Hormozgan province. Since the construction of new docks in recent years has led to changes in the coast of this region, so awareness of the vulnerability of coastal hills can be effective in managing and protecting these hills. The purpose of this study was to assessing vulnerability of sand dunes by model DVI ( dune vulnerability index). Checklist was used to evalouated to vulnerability index. In this research, effective factors in coastal sand dunes, geomorphologic conditions of sand dunes, marine factors, wind processes, vegetation, effects of human activities and management factor were evaluated using checklist. Materials and methods: In this study, data from Google Earth, Landsat, and aerial photos, and questionnaires and field operations were used to complete the checklist. The steps to complete the checklist are as follows: in the first step, the value range for the quantitative variables was determined on the basis of the available structured checklists .Partial vulnerability indices geomorphological condition (GC), marine influence (MI), aeolian influence (AI), vegetation condition (VC) and anthropogenic effects (AE) were calculated as the ratio between the summations of given variable ranks within each variable class (PVi) and the total maximum possible rank within the class. A total DVI ( total Dune Vulnerability Index) was calculated as the average of the five partial vulnerability indices (PV) as per. The protection measure index (PM) was calculated separately from other factors. Lastly, the residual value as the difference between DVI and PM (DVIPM) has been calculated to describe the stability of the dune system. In the studies by Davis (1995) to calculate the vulnerability index, referred to as (VI) the calculation of the partial Vulnerability Index is not done, and the vulnerability score from the division of the total variables obtained from all the group of variables, based on the maximum total sum of the concessions of the entire group of variables, is obtained for each site. Results and discussion: Partial vulnerability (Pv), for geomorphologic agent, is above 0.75 in all sites and the degree of vulnerability is very severe because of characteristics of the sand dunes of the region, including low height, slopes over 30 degrees of their upward slopes, finetogood sorting. The vulnerability to wind processes in all areas is above 0.5 and shows a high sensitivity to this factor. One of the reasons for wind processes is the small average of the diameter of coastal sediments in this area, because fine sands are exposed to retrogressive waves and are more sensitive to erosion, so beaches with fine sand grains have less resistance to erosion have. The low vegetation of the hills in the side of the sea, in the distance between the hills and the maximum of fashion and the relatively high percentage of uncovered areas, are other factors of high hills' sensitivity to wind processes. The degree of vulnerability to vegetation condition is very severe in sites 4, 5 and 6, and is low in enclosures 1, 2 and 3. Compared with 1966 aerial photos and satellite imagery from 2000 to 2016, vegetation increased than in 1966 and 2000, due to planting and plant care by government office like office of resource natural in Hormozgan. The level of vulnerability to the human factors of sites 1 and 2 is modest and in the rest of the sites is negligible. With the use of aerial photographs and satellite imagery, during the years mentioned above, the amount of roads in this area has been increased and in some areas the road passes through the hills. During these years, some parts of the hill for construction have been cleared. In addition, the construction of three new berths of 3 Sirik (2007), Ziarat (2012) and Taheroi port (2013) has also been associated with shore changes. Due to the field visits and the results of the questionnaires( interviews with local people and experts) show no management action such as specifying areas with access restrictions, and so on to protecting beaches. The only protective action is the planting of seedlings in sites 1, 2 and 3, The only protective action is the planting of seedlings in sites 1, 2 and 3, by natural resources office. Coclusion: The overall vulnerability (DVI) in all areas was moderate. Among the investigated factors, the morphological status of sand dunes, the factor of wind processes, have the most effect on the vulnerability of hills. The results for the DVIPM index indicate that all sites need quick management. Based on the obtained equilibrium index, there is no equilibrium between vulnerability and hill management in any of the sites indicating lack of management or inadequacy. One of the reasons for lack of management or efficent management seems to be that is not a certain organization responsible in this regard. Comparison of the two methods for the calculation of vulnerability, the first method (DiPanjun, 2014) and the second method (Davis, 1995) shows that In both methods, the severity of the vulnerability of the sites is moderate. There is no difference between the qualitive results obtained in two methods.