عنوان مقاله [English]
Karst geomorphic landscapes, which are formed as a result of dissolution of rock ,s ingrediets by natural waters, play an important role in geological diversity and are considered as one of the management priorities. These studies should make a significant contribution to the qualitative and quantitative management and protection of these resources against pollution from human activities. What is important is that the identification and zoning of karst areas has an important impact on the management and planning of these areas. The connection between surface water and groundwater is achieved through precipitation. The denser the joints and fractures and the more rainfall, the better the groundwater resources. Groundwater flow in geological formations depends on porosity and permeability. Tectonic factors and karstic landforms play an important role in permeability and groundwater recharge. Therefore, it is necessary to identify and determine the boundaries of karst areas.
Baqmach ,s basin is located 30 km from Chenaran city and 80 km northwest of Mashhad. This area is 96.5 square kilometers. This basin is located in the geological zone of Hezar Masjed-Kopeh Dagh. This basin has spring-winter rainfall and the annual average of rainfall is 250 mm. Water resource in this region include the groundwater and surface water (springs, wells and aqueducts). Due to its carbonate structure and tectonic lines, it has a high potential for karst.
The purpose of this study is to identify and zoning karst development by using Fuzzy logic model in the Baqmach ,s basin.For this purpose, information layers including lithology, tectonics, precipitation, temperature, slope, altitude, vegetation and land use were prepared. Information layers were prepared using ARC GIS software. These layers were defined as fuzzy functions based on experts' opinions and knowledge of relationships, criteria and field investigation and have been compared.
According to the type of relationship of each parameter with the karst formation phenomenon, the membership function of vector layers is determined. In increasingly uniform, their numerical value is greater than one. In uniform reductions, regions with smaller numerical values have a greater impact on karst development. In this study, only the slope and reducing tectonic layers are uniform. That is, karst development is greater in areas with lower slopes and areas that are less distant from faults and fractures.
Then these layers were standardized using ANP model. The structure of the network was adjusted through questionnaires and expert opinions. Fuzzy logic model was used to zoning areas with karst development potential. The information layers obtained are combined using the fuzzy logic method. Fuzzy operator multiplication was used to adjust the very high sensitivity. The sum operator is also used for very low fuzzy sensitivity. The gamma operator has a moderating role. The gamma operator is closer to reality and the final map of areas with karst development potential was obtained and the area of each class was determined. The zoning map of surface karst development was prepared with a gamma coefficient of 0.9 .
The studied basin was classified into 5 classes in terms of karst development. These classes include karst with high development, karst with relatively high development, karst with medium development, karst with low development and no karst development. The results showed that 16.3% of the region's area is in the karst region with high development potential and 33.7% is karst with high development. This area corresponds to the formations of Mozdoran and Tirgan with limestone and dolomite lithology. 6.6% of the region's area is in the karst class with medium development and 3.6% is karst with low development, and 39.8% is without karst. The central part of the basin has very little potential for karst formation. The area of this floor is about 43.4 %. This section is located in the karst region, which is less developed and without karst.
The lithological coefficient of the area has the highest weight with a value of 0.233.The lithology parameter has been the most important factor controlling the karst development potential in the studied area And the factors of drainage density and land use have the lowest weight. They have the least influence on the current karst formation of the basin. The results show that the factors of lithology, precipitation, temperature and altitude have played the most important role in the current karst development in this region. The investigation of the geological units of the region and their lithology shows that only Mazderan and Tirgan formations are effective in the formation of karst resources. According to the results of using the ANP-fuzzy model, it can significantly help in identifying and zoning karst areas.