Integrative use of GNSS and InSAR data – a case study of landslide on the Thracian rocks coastal slope

Abstract

The main objective of this research is monitoring of landslide areas by integrating results from interferometric images, and GNSS data from permanent and local geodetic networks. This study is providing reliable information with regard to the hazard geo-processes taking place in the region of the landslide area Thracian Rocks. To accomplish the aforesaid the first step was to create a local archive of about 400 SLC images from ESA operated mission Sentinel-1 starting from the beginning of 2015. In this archive data from ascending and descending satellite orbits were included in order to increase the reliability of the information derived from SAR data. Due to considerable occurrence of vegetation in the studied area, which is recognized as one of the factors increasing the decorrelation during DInSAR processing, the authors processed mainly scenes with minimum availability of leaves on the trees and shrubs – autumn and spring. The geological setting of the landslide region reveals a narrow strip formed by old landslides that have an average width of 400–500 m and steep slopes of 40–50 m at certain locations. From this setting it was established that the landslide bodies have been formed by 3–4 visible linearly oriented steps and landslide packages with different heights creating negative ground forms with permanent or temporary swamps. Besides the ancient landslides a recent active local landslide processes occur forming recent landslides. In the framework of this study a control geodynamic network covering the landslide area located in the surroundings of Thracian Cliffs golf club was established. In it included are 10 points stabilized with metal pipes which are used to monitor deformations in this area. An advantage of the approach should be pointed out the possibility to map areas that are inaccessible by other means.