ارزیابی و پهنه‌بندی تحول کارست حوضه آبریز غار سهولان مهاباد با استفاده از روش تحلیل سلسله مراتبی

شناخت عوامل موثر در تحول کارست و پهنه بندی تحول آن در زمینه مطالعات مربوط به منابع آب کارست دارای جایگاه ویژ ه ای است. هدف از این پژوهش ارزیابی و پهنه بندی پتانسیل توسعه کارست در محدوده غار سهولان در جنوب شرق شهرستان مهاباد در استان آذربایجان غربی با استفاده از روش ahp می باشد. در این تحقیق لایه های اطلاعاتی لیتولوژی، شیب، جهت شیب، ارتفاع، فاصله از آبراهه، فاصله از گسل و کاربری اراضی به‌عنوان نقشه های عامل در نظر گرفته شدند. همچنین به‌منظور استخراج مدل پتانسیل توسعه کارست، لایه‌های فوق در محیط  gisفراخوانی شدند. لایه های اطلاعاتی مختلف با اعمال قضاوت کارشناسی (به‌ویژه با عنایت به وجود غار سهولان به‌عنوان برجسته‌ترین شاهد پالئوکارست) و اختصاص وزن به هر لایه در نرم‌افزار  expert choice و بازدیدهای میدانی به‌صورت نقشه های معیار طبقه‌بندی شدند.  درنهایت با توجه به وزن به‌دست‌آمده نقشه پهنه‌بندی توسعه کارست به دست آمد. نتایج به‌دست‌آمده نشان داد که از کل مساحت حوضه آبریز غار، 42.88 درصد در طبقه کمتر توسعه یافته، 33.37 درصد در طبقه توسعه نیافته، 16.92 درصد در طبقه متوسط و 6.83 درصد در طبقه توسعه یافته قرارگرفته است. ازاین‌رو، عامل لیتولوژی منطقه باارزش 0.667 بیشترین وزن و مهم‌ترین عامل کنترل‌کننده پتانسیل توسعه کارست در منطقه موردمطالعه بوده است و عامل کاربری اراضی باارزش 0.043 کمترین وزن را به خود اختصاص داده است که کمترین تاثیر را در کارست زایی کنونی حوضه به خود اختصاص داده است. نتایج نشانگر آن است که به ترتیب عوامل زمین‌شناسی، هیدرولوژی، توپوگرافی و عوامل انسانی مهم‌ترین نقش را در توسعه کنونی کارست در این منطقه داشته اند و وجود غار سهولان به‌عنوان شاهد برجسته پالئوکلیمایی بر نقش فاکتورهای اقلیمی دیرین در توسعه کارست گذشته منطقه دلالت دارد.

Evaluation and Zonation of Karst Developing in Sahoolan Cave Basin, Mahabad using Analytic Hierarchy Process method

Karst areas are qualified by unique hydrological and geomorphic features, including welldeveloped underground drainage and specific landforms resulting from dissolution processes. Karst areas and caves hold other important resources: they are often among the most scenic areas, able to attract large numbers of visitors. They are also a perfect arena for educational activities. Karst landscape and underground caves related to them are often created by chemical dissolution of rocks. Karst landscapes show a broad variability in different parts of the world. They may include large and dense doline fields, extensive poljes, and caves of multiple genetic types, whose genesis is largely controlled by the hydrogeological context, lithostratigraphical factors, and the long term geomorphological evolution. Karst area has an important role in feeding the aquifer. Therefore, understanding the factors contributing to the development and zoning development karst in the field of studies related to water resources of the karst is a special place. The aim of this study is to identify and zoning of development potential of karst in the range of Sahoolan cave in southeast of Mahabad county, west Azerbaijan province using analytic hierarchy process (AHP) method. In this research, has been the degree of importance of influence factors in the development of karst in the range Sahoolan cave in South East of Mahabad city. Sahoolan watery cave is located in Northwest of Iran and 43 km far from southeast of Mahabad with geographical coordinate’s 36˚ 39’ 21 in northern and 45 ˚ 57’ 13 eastern longitude. The cave is can be accessible by Mahabad Bukan main road (Borhan road) and threeways Eisa kand village. Cave created in the rocks of limiston dolomite belongs to Permian geological age. This cave comprised two parts is dry and watery. Also, cave located in the recess rocky, in the southern part of the hill area near the Sahoolan village. The main entrance to the cave is a place calledKone couter in Kurdish language, that it is meaning of a place have a large number of pigeons. This place coincides with watery part of the cave that located 1766 meters from the sea level. The entrance area of cave is plane land with is a horseshoe shape. Several shrubs in the name of Tavk, which is rare in Iran, are protruding from the cave. Another entrance of the cave is not far from cave and it is located at 1795 meters from the sea level, which called in Kurdish languageKone Malan. Geological features inside the cave shows that the cave in practice by standing water, no running water is created. The cave was initially completely filled with water. During the end of development of the cave, the water level has gone down and this geological action has been created more pathways and booths inside the cave. In order to more identify and analysis, data layers including lithology, slope, aspect, elevation, distance to  river, distance to faults and land use in the catchment that cave is located inside it, were prepared using Arc GIS 9.3. Different layers by applying expert judgment and field works were classified as criteria maps. Also, all layers according to the degree of importance were ranked from 1 to 9. Furthermore, each layer based on priorities in potential of karst development by using Analytical Hierarchy Process (AHP) method was allocated suitable weighted. After that, raster maps all the above mentioned parameters in Arc GIS 9.3 software were prepared. Then each classified raster maps by Raster Calculator in GIS were multiplied in their obtained weight in Expert Choice software. The zoning map of karst developed for the study area was created in four classes including undeveloped, low developed, moderate developed and developed. The results shown that 42.88% of the study area was located in low developed class, 33.37% in undeveloped class, 16.92% in moderate develop class and 6.83% in developed class. Hence, lithology factor with high weigh (0.667) was important factor in development potential of karst in the Sahoolan cave but land use with low weight (0.043) was least impact in development potential of karst in the study area. The final results indicate that the geology, hydrology, topography and human factors have the most important role in the development of karst in the study area.