Geodiversity assessment using qualitative-quantitative GI index (Case study: Lorestan province)

The diversities on the planet are divided into two categories: biodiversity and geodiversity, which have attracted a lot of attention today. It has been proven that geodiversity can be an important foundation for biodiversity, for this reason it has been the focus of different people and communities. Among them, geodiversity means natural variations related to geological, geomorphological, paleontological, mineral, tectonic, soil, topographic and hydrological factors. In fact, these are heritage items that should be geologically protected for today's societies and future generations. Geodiversity is evaluated with three qualitative, quantitative and qualitative-quantitative methods. Qualitative-quantitative methods are using a combination of quantitative data (such as digital models) and qualitative data (questionnaire); which has more reliable results in geodiversity evaluation. One of these quantitative-qualitative methods in the field of geodiversity assessment is the (GI) model, which was introduced by Betard & Peulvast (2021). which this research seeks to use in addition to using this index in one of the mountainous regions of Iran (Lorestan province), its geodiversity for the purposes of To evaluate geological protection and benefit from its geosystemic values and services.

The studied area is Lorestan province in the western plateau of Iran, where a part of the Zagros mountains passes through it. Lorestan province is located in three geological structural units: Sanandaj-Sirjan, high Zagros and folded Zagros.The soils of Lorestan province can be divided into 5 main categories based on the characteristics and factors that are effective and measurable in the formation and development of soils and their ability to grow and develop plants. In terms of geomorphology, this province has various forms. This research has used the index (GI), which is a quantitative-qualitative method and is compatible with the use of geographic information system (GIS) and questionnaires in order to evaluate the geodiversity of Lorestan province. Its sub-indexes are lithological diversity, geomorphological diversity, hydrogeological diversity and diversity of soil landscape units.

In our study area, the lithological diversity was first calculated without considering the erodibility, and in the next steps, the hydrological, soil and geomorphological landscape units were calculated. Then weights were assigned to each of the diversity indicators using the hierarchical analysis process (AHP) and the results obtained from the hierarchical analysis process showed that the indicators of geomorphological diversity, lithological diversity, hydrogeological diversity and diversity of units. The soil landscape had the highest score respectively. Then, each of the sub-indices of geodiversity was multiplied by its weights and finally the geodiversity assessment map of Lorestan province was created. (679% square kilometers) of the area of the province is in the very high geodiversity class (V5); These areas include: Shires Canyon, Sepidasht folds and Hogback Robat, oshtorankuh and North Poldakhtar protected area. Shires Canyon due to having various karst forms and lithological diversity, Sepidasht Heights due to lithological, hydrogeological and geomorphological diversity and diversity in alluvial and structural landforms, Oshtorankuh due to lithological, hydrogeological, soil landscape units and geomorphological and karst landforms and affected by the tectonic dynamics of the region and Melawi and Pol-e dokhtar region have the highest geodiversity due to lithological, hydrogeological and geomorphological variations.

Geodiversity evaluation indicators are divided into three categories: quantitative, qualitative and quantitative-qualitative. The output of the geodiversity evaluation index and its related sub-indices were divided into five classes based on natural breaks lines: very low (V1), low (V2), medium (V3), high (V4) and very high (V5). In order to evaluate the final geodiversity of Lorestan province, the weight of each criterion was calculated using expert opinion and the Analytical Hierarchy Process (AHP). Then, the information layers of each of the sub-indices related to lithological, geomorphological, hydrogeological and soil diversity were added together based on the weights and the geodiversity map of Lorestan province was created. Based on the weights received by each of the sub-indexes of geodiversity evaluation, geomorphological diversity and lithological diversity have obtained the highest points respectively, which indicates the high role of these two factors in the evaluation of geodiversity of a region. The results obtained from the geodiversity assessment show that 1% of the area of Lorestan province (679 square kilometers) is in the very high diversity class of geodiversity (V5); which include: Shires Canyon, Sepidasht fold complexes, Oshtorankuh protected area and north of Poldakhter city. Also, Sefid Kuh Khorramabad and Qali Kuh Aligodars are also in the high diversity class of Geodiversity (V4). The results of this research can be used by planners and managers for planning related to Geoconservation, benefiting from ecosystem and geosystem services and Geotourism.