Investigating Effective Factors in the Evolution of Karstic Sinkholes in Gachsaran Formation Using the Fuzzy Model(Case Study: Maroon Plain, Kohgilooye and Boyer-Ahmad Province)

The presence of formations containing gypsum layers will enhance the formation of gypsum karst forms. The thickness of the gypsum layers and the quality of the mentioned beds influence the formation of such landforms. The Maroon plain is located in the folded zone of the Zagros Mountains in Kohgiluyeh and Boyer-Ahmad Province. The existence of the Gachsaran Formation and occurrence the karst phenomena (among which sinkholes are the most significant) in this plain have a very destructive impact on the roads, facilities, farmlands, residential units, and the reservoir of the Maroon Dam located in the plain; but unfortunately, this phenomenon is not well-known and well-studied. In this research, karst evolution zoning map was prepared using the fuzzy model; to produce this map, ten environmental factors including the slope, slope direction, geology, distance from Knick line, distance from flow line, distance from the river, elevation, land use, climate, and the NDVI Index were used. The results of this study demonstrated that 55.2% of the study area is situated in the zero-risk zone because it is situated out of the Gachsaran Formation realm and lacks the gypsum layers; as well, 11.2% of the area is in the high-risk zone, 18.5% in the medium-risk zone, and 15.1% in the low-risk zone. Field observations and studying the zoning map indicate that the main factors influencing on the karst evolution of this area are slope and streamlines which superimposed on the gypsum layers.