Calculation and Analysis of Geodiversity Case study: Eshtehard County

  In recent decades there has been an increasing interest in the earth natural events and this has led to the development of three concepts in the world of science. Geodiversity, Geotourism and Geoconservation. “Geodiversity” can be defined as the natural range (diversity) of geological (rocks, minerals, fossils), geomorphological (land form, physical processes) and soil features. It includes their assemblages, relationships, properties, interpretations and systems.
There is as much geodiversity in the world as biodiversity. Geodiversity and biodiversity are concepts that evolved from the World Biodiversity Convention, in 1992, in Rio de Janeiro, Brazil (Rio-92). Serrano and Ruiz-Flaño (2007) and Serrano et al. (2009), through detailed geomorphological survey, applied the calculation of the spatial distribution of geodiversity in Spain, based on the study of a wide set of mapped elements of geomorphology, geology, hydrology, soil, and active processes.
Zwoliński and Stachowiak (2012) carried out research on geodiversity in a protected area that also served as touristic attraction. The evaluation carried out based on some elements such as waterfalls, according to their size, kinds of rocks, cavities (according to their size), shapes of land, slopes, presence of lakes, altitude, watercourses on cliffs, soil, and geoecological structures. Instead of a variety of elements, the applied method was based on an algebra of maps, as elements were given different scores. The authors concluded that mountains with steep cliffs are more geodiverse areas. Manosso & Nóbrega (2015) calculate and analyzed the distribution and the diversity of abiotic elements in landscape units. The sample units were compared according to geological, geomorphological, hydrographical, and pedological elements, as well as land use and habitation.
Haririan (1990) was the first one presented a definition of geodiversity in Iran. In his view, the formation of geological diversity depends on the internal and external processes diversity. Sepehr (2013) has expressed the natural hazards and geodiversity are paleogeomorphological evidence. As the geodiversity has been affected by complexity of process and time, he has presented a geo-system analysis. Ba-tajrobe et al. (2016) have offered the geodiversity map of Mashhad city based on the analysis of landforms sensitivity to erosion and weathering.
This work aimed to perform a quantitative evaluation of geodiversity in 3 unit of Eshtehard County, on the southern part of Alborz province. In this study, 1:50,000 scale topographic maps, 1: 100,000 scale geological maps, Googlearth satellite images, Digital Elevation Models (DEM), Geographic Information System (GIS), library studies and field observations were used. To check the type and distribution of geodiversity elements in the study area, the following five steps were performed:The study area was determined using maps and satellite images.
Geomorphological units based on the three units of landscapes including plain, hills and mountains were determined.
Ground elements in the region, using satellite imagery, topographic maps, geological maps, soil maps, hydrographical maps and field observations were identified.
Required maps using GIS mapping and photographs of the field works, prepared and evaluated.
Geodiversity index was calculated for each unit and comparative analysis was performed.
In order to evaluate geodiversity condition in studied are, geodiversity index (Serrano and Ruiz-Flaño, 2009) was used.
GD= (Eg.R)/(Ln S)
GD Geodiversity index
Eg Number of abiotic elements
R Roughness of the relief
Ln S Log of the sampling area
Index (R) was calculated using the topographic relative position method in and GIS and was placed in Formula 1.
The final step is presentation of the concept of protection and maintenance conditions in the study area. Abiotic elements diversity in Eshtehard is not only in terms of geological diversity but also in terms of covering the soil, hydrological conditions and landform.
Eshtehard playa is an evidence of environmental changes during the cold periods of Quaternary. According to previous studies, it has been an old lake bed during quaternary. Salt River, in this context, is ongoing and will eventually it connects to Hoz-e-Sultan lake.
Rainbow-colored hills in north of the Eshtehard are one of the most remarkable landscapes in the region. There are a seasonal lake within colored hills, salt cave and two different springs that are geodiversity features in the hills. The marl hills and Stone houses in the northwest of Eshtehard, are another perspectives of the unit G1.
South of the Eshtehard is surrounded with Halqe-dar and Tavreh mountains. The maximum height of the mountain is 2,000 meters above the sea level. The important differences in unit G3 rather than G2 and G1 are numeral springs and variable volcanic stones.
The highest (R) is related to unit G1 with the 0.4745 GD. Most of the abiotic elements are in G3unit (60 elements) and the least are located in G1 (30 elements).
After calculating the parameters, we realize that the greatest geodiversity index is belonged to G3 (4.716) in the South of Eshtehard area. This is because of high level of diversity in hydrologic and lithological elements.
Finally, because of importance of abiotic phenomena in studied area and high level of geodiversity, geoconservation activities is necessary for valuable land resources; furthermore the capacity of geotourism must be evaluated and managed