Analysis of Rock Cracks in Naqsh-e Rostam Historical Area by Remote Sensing

Cultural heritage sites are threatened from a variety of natural and anthropogenic factors. Innovative and cost effective tools are needed to protect them via systematic monitoring of landscapes and cultural heritage sites. In this study, the overall risk in the Naqsh-e Rostam area, as a case study, was assessed in a multidisciplinary approach, based on the remote sensing techniques and Geographical Information System (GIS) analysis. Naqsh-e-Rostam is known as an ancient periphery which is located in northwest of Persepolis in Fars (nowadays Shiraz), Iran. The oldest relief at Naqsh-e-Rostam is severely damaged and dates back to 1,200 B.C., while there is a rock relief thought to be Elamite, originally. Four tombs belonging to Achaemenid kings are carved out of the rock face and seven oversized rock reliefs at Naqsh-e-Rostam depict the monarchs of the Sassanid period. In Sasanian epoch, Naqsh-e-Rostam site was very important due to its religious and national role, where Ernst Emil Herzfeld and Heidemarie Koch estimated its ancientness about 4,000 B.C. This historical site, which is one of the most unique ancient monuments in Iran, is suffering from some problems such as erosion and deep cracks, due to mainly the climatic and geological characteristics of the region. Currently, several damages threaten this site, which are also remarkable on the high reliefs and on the ground, vicinity of the reliefs. These monuments are located in orographic mountains which expose overall to interaction with their surrounded environment. Therefore, existing deterioration as well as erosion process is mainly due to the climatic conditions and geo-environmental factors that cause such challenges. The aim of this study was to analyze the unexpected appearance of a deep fracture with unknown reasons in this site during the recent years and to find the basic phenomenon for the appearance and development of these fractures. First, several natural and anthropogenic hazards were mapped using different remote sensing data and methodologies. All data were gathered from satellite images and products. Then, the results from each hazard were imported into a GIS environment in order to examine the overall risk assessment based on the Analytic Hierarchy Process (AHP) methodology. The results showed that the methodology applied was effective enough in the understanding of the current conservation circumstances of the monuments in relation to their environment, as well as in the prediction of the future development of the present hazards. Transverse and main cracking are dominant damages that will result erosion in whole of these works. The focal pressure sources, which produced once drainage and haulage of water stream along the crack systems in the rock surfaces, was studied with Aerial Photography and Satellite Imagery, and analyzed with respect to GIS system. Finally, the gullies effect was identified in the back of the rocks.