Determination of surface displacement on the landslide in Kłodne (Limanowa community, southern Poland)

Abstract

Examination of the landslide in Kłodne was carried out in 2013 and 2014. The work was divided into two parts: geological engineering investigations (mapping of the external borders of the landslide) and geodetic surveying (photogrammetric studies and monitoring of surface movements). The boundaries of the landslide were marked using a Garmin eTrex GPS receiver and a geological compass (Freiberg). The boundaries have not changed and is convergent with previous studies. In the south-western part of the landslide the boundary is blurred as a result of anthropogenic transformation of the area. In the south-eastern part (as at May17, 2014) about 200 m3 of the colluvial material has been moved. Photogrammetric studies were based on the analysis of aerial photos from May 26, 2009 (prior tothe landslide formation) and on the orthophotomap created from images taken in July 2010, after the formation of the landslide. Displacement vectors were determined by comparing the locations of specific terrain details in the pictures taken before and after the mass movements occurred. In the upper part of the landslide the maximum horizontal displacement value was 87.7 m, the minimum was 6.2, and the average – 84.5 m. In the lower part of the landslide the horizontal displacements amounted to 65.5 m, had a minimum value of 10.3, and an average of 54.8 m. In the last stage of the study the base measurement network was created. It consisted of 68 points stabilized in the ground. The measurements were performed using the static GNSS observations method and linear-angular measurements carried out with a precise total station. In 2013, horizontal displacements ranged from 1 to 8.1 mm, and vertical ones ranged from –9.8 to 13.5 mm. In 2014, there were displacements observed in the vicinity of the main slope. They were directed to the south. The horizontal displacement vector has reached values from 2 to 94 mm, and the vertical vector was from –63 to 16 mm