تعیین آسیب پذیری و ریسک مخاطرات فرسایشی بندر آستارا

گرمایش کره زمین طی قرن بیستم سبب افزایش سطح تراز آب اقیانوس ها گردید و به زیر آب رفتن نواحی گسترده ای از مناطق ساحلی و بروز پدیده های فرسایشی از پیامدهای نامطلوب آن بود. تعیین شدت آسیب پذیری و ریسک مخاطرات فرسایشی در ناحیه ساحلی بندر آستارا بعنوان هدف اصلی تحقیق محسوب می شود. با مطالعه و تفسیر تصاویر ماهواره ایبخش اشکال مورفولوژیکی ساحلی شناسایی گردید. در بازدیدهای میدانی وضعیت مورفودینامیک رسوبی و ساختار هندسی بخشخشک ساحل در پنج ایستگاه اندازه گیری مستقر در سه زون ساحلی پایش شد. با انجام عملیات نقشه برداری و هیدروگرافیساختار هندسی ساحل آستارا اندازه گیری و خصوصیات بافتی رسوبات بستر دریا ارزیابی گردید. با آنالیز تصاویر ماهواره ای و عکس های هوایی در نرم افزار gis، خطوط ساحلی دریای خزر در دو پریود با فاصله زمانی 52 ساله مقایسه شد و میزانجابجایی خط ساحل محاسبه گردید. نتایج اصلی نشان می دهد که میزان نرخ جابجایی خط ساحلی در ناحیه شهر آستارا متفاوت است. شیب بسیار ملایم ساحل آستارا سبب افزایش شدت آسیب پذیری در زمان افزایش سطح تراز آب دریای خزر شده است و ریسک مخاطرات فرسایشی در نواحی جنوبی بندر آستارا بعلت دخالت های انسانی نسبت به مناطق دیگر آنبسیار زیاد است. در مدل سناریوهای نوسانی عکس العمل ساحل آستارا موجب بروز چالش های جدی و تهدیدات زیستمحیطی مختلف خواهد شد. بطوری که با افزایش 2 متر سطح تراز آب دریای خزر 30 هکتار از اراضی ساحلی دچار آبگرفتگی می شوند و کاربریهای اقتصادی متنوعی از بین خواهند رفت.

Erosion vulnerability and risk assessment in Astara port

Extended AbstractIntroductionWater is the principal source of economic development, social security and poverty reduction. The value of water source leads to enhancement of management measures to maintain its quality and quantity by communities. Environmental changes and human activities effect on the quality and quantity of water. Urban growth, increasing industrial activities and overuse of chemical fertilizers in agriculture result in pollution of groundwater and surface water which have adverse effect on the health of human beings, animal and plants. Groundwater is the primary source to supply agriculture and drinking water hence recognition and awareness of groundwater quality and the water classification based on the number of various elements of them will assist us in making management decisions and decline groundwater pollution. Groundwater is particularly important in arid and semiarid areas. On the other hand groundwater deterioration, both in quantitative and qualitative terms is important in water resources management of these areas.The concentration of common ions in water is one index for assessing water quality. Groundwater quality index (GQI), a combination of parameters for water quality, that constitute a reliable tool in defining aquifer vulnerability is used to investigate the spatial variability. GQI shows the data related to the water quality in an explicit manner. This index presents a way of summarizing the overall qualitative condition of water which is understandable for the audience. Materials&MethodsYazdArdakan plain has been faced with significant reduction of groundwater level in recent years. So, it is expected that the studying groundwater quality index can be effective for aquifer management in this plain. In this research GQI was used in order to study the distribution of major water ions including Calcium, Magnesium, Sodium, Chloride, Sulfate and Total Dissolved Solids (TDS); and zoning groundwater quality using ArcGIS10.1. The data of 53 piezometric wells provided by Iran Water Resources Management Company were used to study the status of temporal and spatial changes of GQI in YazdArdakan plain. Water quality sampling campaigns were conducted during most vulnerable periods of early and late summer to ensure the representativeness of the targeted GQI under worst case conditions. Quality zoning maps were provided for 2003, 2006 and 2011. For this purpose, data were evaluated in GS+ 5.1 software, after calculation, the best model with the lowest estimated error was selected for zoning water quality parameters. Because of the lowest estimation error, Kriging, Gaussian and Spherical variogram models were selected as appropriate interpolation method for zoning the quality parameters. WHO standards were used to compare and investigate the quality status of the water. The water qualitative groups in the GQI map were divided into 5 classes of good, acceptable, medium, inappropriate, and poor, scoring from 0 to 100. The class which is close to 100 shows better quality and the class which is close to 0 shows lower quality. Results & DiscussionThe results showed that YazdArdakan plain is located in average and acceptable classes according to GQI index. The highest and lowest amount of Groundwater Quality Index (GQI) were in the west and north of the study area, respectively. Moran's I spatial autocorrelation index, GQI and all chemical studied variables except for magnesium have cluster spatial distribution pattern, but Magnesium have random spatial distribution pattern. Three parameters of Total Dissolved Solids (TDS), Sodium and Chloride having the highest coefficient ranking have a highest impact on GQI, respectively. On the other hand, these parameters have a high weight and GQI is more sensitive to them. In fact, these components in YazdArdakan plain groundwater have more impacts on GQI model and their removal will cause greater changes in GQI. Therefore, they should be carefully evaluated and monitored. Generally, it can be concluded that GQI has the descending trend in the study area and land use has the important role in reducing GQI index and water quality. It can also explain the overall quality of groundwater and its threats in various uses of water. Finally, the regions with poor groundwater quality can be targeted for detailed studies and monitoring programs. ConclusionAccording to the results, due to the nature of natural phenomena such as drought, their complete removal is not possible. The only principled way to prevent dangerous consequences of the water table decline and reduction of groundwater resources quantity and quality is the correct and systematic use of water and avoidance of uncontrolled groundwater withdrawal.