نوع مقاله : مقاله پژوهشی
1 دانشجوی دکتری ژئومورفولوژی، دانشکده برنامه ریزی و علوم محیطی، دانشگاه تبریز .
2 استادیار گروه جغرافیای طبیعی، دانشکده جغرافیا، دانشگاه تهران.
3 دانشجوی دکتری ژئومورفولوژی، گروه جغرافیای طبیعی، دانشگاه تهران.
4 دانش آموخته کارشناسی ارشد مخاطرات آب و هوایی، دانشگاه محقق اردبیلی .
عنوان مقاله [English]
Karst is a set of geological processes and phenomena resulting from the dissolution of rocks . It is characterized by forming’s and Openings, erosion of formations and conditions of the stones, a specific type of water circulation , a certain type of local topography and the special regime of drainage network. Karst outcomes usually categorized as surface, subsurface and bathetic or internal complications.formation of Karsty phenomena such as karst pits, caves, Pole, graik and great fountains are As a result of secondary porosity.( Floria, 2005)
Karst sinkholes are known as a karst erosion landforms and a proper criterion
to identify Environment conditions in different periods. (pike,2011) Given the importance of Karst sinkholes, identifying and mapping distribution of karst sinkholes and their characteristics of forms are the needings of the Environmental science and geomorphology.( Van.Beynen ,,2011) Landforms are representing the processes that affect the Earth surface in the past and present and provide important informations about The characteristics and potentials of the Earth.( Bates,1987) quantitative and numerical geomorphology studies, spatial and statistical features and the correlation of spot features. also the basic principles that Geomorphomety emphasizes on that is the relationship between the form of roughness and it’s numerical parameters for explaining Processes that are involved in the formation and evolution of landforms.
Kermanshah plain with an area of 5/739 km2 is located on the west side between 34 ° and 8 minutes and 32 seconds to 34° and 33 minutes and 52 seconds of north latitude and 46 degrees 22 minutes and 54 seconds to 47 degrees 00 minutes 31 seconds of East longitude from the Greenwich meridian and an average height of 1410 meters above sea level.
The basis of the identification and classification of landforms is based on Geomorphomety .Geomorphomety is about the quantity of the primary elements of morphology of the land such as slope, Slope orientation, height and relative height difference between elements, the elements relative location to each other, the condition of drainage network and Convexity or concavity of the elements.(Dehn,2001) Input data in the Geomorphomety studies is the digital model of height in Raster form and with square cells that In some cases the digital model of Earth surface could be replaced with it.( Mull,2002) In this research in order to identify the quantitative characteristics of the sinkholes in the region of Kermanshah Plain Geomorphomety indices including second grade derivatives of RTP index , indices of curvaturas parameters and finally sinkholes clustering are used. Important Curvaturas parameters including curved slope parameters (the amount of tilt in all directions), curvature profiles (at all levels) and the curvature of the plan (at all levels). Calculation of all types of curvature in digital model of raster elevation is pixel by pixel and for each cell a quartic poly-Tamyal equation is used (Equation 1 and 2)(Bishop,2000):
1) Z=Ax2y2 +Bx2y+Cxy2+Dx2+Ey2+Fxy+Hy+1
2) (SD – min D) / (max D-min D)
To extract geo-morpho-metric indicators of Kermanshah Plain of digital elevation model with a resolution of 10 m, 1: 25,000 Topographic maps of mapping organization prepared and used for Geomorphometric analyzes .in order to evaluate the quantitatively landforms formation 55 units (sinkholes) were identified. Input data In the first phase are slope layer, sinkholes layer and DEM, which after entering each layer to zonal statistic as table command tables obtained. After extraction of Geomorphomety indices, average values and The maximum and minimum for each class, landforms obtained. Finally cluster analysis and output maps obtained from average data.
Kermanshah plain with elongation morphology, along the North - South, is among a collection of mountain and is limited from the north side to praw-bistoon mountains and from the south to White Mountains.
In this region There are various forms of karst area from different landscapes such as sinkholes with enormous distribution. In order to existance of superelevation praw (bistoon and white mountains) in northern and southern regions of Kermanshah Plain, sinkholes affected fold and thrust belt, faults and breakage impact . based on the results we've achieved Sinkholes formations are simple, compound and complex.the role of faults is Dominant in the formation of Sinkholes in this region. The results of the rtp index represents this.the length of a small number of curvature sinkholes (11%) somewhat softened and in areas away from the fault in the lowlands has a softer morphology compared with heights which have jagged and rough morphology. Results of curvature index represents that curvature slope index,profile and plan have more performance in indicating the morphometery features of landslipy Sinkholes. based on the final clustering 89 percent of our sinkholes located on a main cluster And fault factors (tectonic) causes the formation of sinkholes on the heights and In terms of of the genesis and morphometric features they are the same (rugged and rough topography) and there is no dramatic difference between them