Evaluation of Geodiversity Index using Kernel Density Function (Case study: Qezel Ozan basin, Kurdistan Province)

Extended Abstract

Introduction

Rapid environmental changes and the challenges of achieving sustainable development have highlighted the need for better understanding and management of nature. Geodiversity has played a key role in land management and conservation approaches, and its concept has been accepted by scientific societies worldwide. In general, geodiversity is known as a variety of geological phenomena that constitute natural heritage and need to be preserved and protected. Considering the importance, functions and applications of geodiversity, the range of related studies is increasing. In parallel with the conceptual design, so far a set of approaches have been presented to evaluate and measure geodiversity based on qualitative and quantitative methods. The kernel density function is one of the quantitative methods for evaluating and analyzing the geodiversity index. In the current research, the geodiversity index in the Qezal Ozan river basin in Kurdistan province will be analyzed and evaluated using the kernel density function.

Methodology

In this research, data, relevant tools and kernel density function have been used to achieve the geodiversity index, each of which will be mentioned below. The variables include geology, geomorphology, soils, faults and hydrography. Regarding the method of investigation that requires the use of software; ArcGIS software version 10.4.1 has been used in this research. Kernel density can be calculated for both point and linear features. This function is included as an additional tool in the spatial analysis section of ArcGIS software. After entering the point data into the kernel density calculation tool, the parameters of population, cell size, search radius and area units for output map need to be defined. The result will be the kernel density of geodiversity.



Results and Discussion

The variables that have been selected based on the aforementioned method in order to evaluate geodiversity index in Qezel Ozan basin of Kurdistan province are geology, geomorphology, soil science, faults and hydrography. For kernel density evaluation, in addition to the metric coordinate system, all layers need to be in polygon. In this research, for all the layers, the Universal Transverse Mercator System (UTM), which is a metric coordinate system, has been used. Apart from the geological, geomorphological and soil layers, which are polygons, in the first step it was necessary to define the fault and hydrographic layers as polygons. For this purpose, by defining a buffer, the linear layers of fault and hydrography were converted into polygons.

In the output raster map, based on the input layers, the size of each cell was 595.5 meters by 595.5 meters, and in order to increase the accuracy of the search, each cell were defined as 100 meters by 100 meters. The search radius, which is determined based on the spatial relationships of points and a special algorithm, was 3614.7 by default, which was used without change. It should be noted that the final selection of cell size and search radius was achieved after several tests on these parameters. The output metric unit was also determined as square kilometers. Finally, taking into account all the necessary conditions, by entering the point layer in the kernel density operator and selecting the output cell size, search radius and metric unit, the geodiversity index of the watershed was extracted. Based on the numerical values, the resulting map was divided into 5 classes by the natural break method that highlights the difference between the classes. The range of numbers of each class represents the number of points or in other words the number of features per square kilometer. Finally, based on the numerical index of geodiversity in each class, a qualitative range including very low, low, medium, high and very high density was extracted.

Conclusion

The final map of the geodiversity index shows that the range of points in the cells of the output map varies between 0 and 166. The highest density or in other words the highest geodiversity can be seen in the west of the basin. In parts of the north, east and south of the basin, smaller centers with the greatest value in terms of geodiversity can be seen. The important point is that the highest geodiversity index in the west corresponds to the heights of Saral and Chihl Cheshme, which are important geotourism areas of Kurdistan province. This feature is also true for Bijar and its northern areas, as well as the important heights of Bair and Parishan in the south of Qorveh. The lowest amount of geodiversity can be seen in the areas in the southwest and southeast of Dehgolan city and in the east and southeast of Qorve city. These areas, which have the lowest value in terms of geodiversity index, correspond to the flat plains of the basin. The amount of geodiversity in other sectors is in the range of low to high variation.

The evaluation of the importance of the variables or inputs shows that the geomorphology was the most important in the evaluation of the geodiversity index. The reason for the high value of this variable can be the great variety of landforms in the Qezal Ozan basin. In preparing the geomorphological map of the basin, in addition to volcanic, glacial, river, karst, etc. landforms, adding topographical landforms including mountain, hill, and plain units has increased the diversity and importance of this variable in the model. The hydrographic and geological information layers are ranked second and third with a slight difference. Drainage density in the basin is very high due to the wide spread of erodible geological units; So that the Badlands have a significant dispersion. Geologically, Qezel Ozan basin has a remarkable diversity. The layers of fault and soil are ranked fourth and fifth, respectively. Faults can be seen everywhere in the basin. Their highest concentration is in the western part of the area. The soil map of the basin does not have much diversity and only includes seven soil types.