engleski

Rockfall Monitoring by Terrestrial Laser Scanning - Case Study of the Rock Cliff at Duće, Croatia

Dalmatia region in Croatia has dozens of registered active rockfall zones. Virtually whole area along main coastal road from city of Split to town of Omiš is a potential danger zone for inhabitants and community infrastructure. Every year, in periods after heavy rain and/or considerable low air temperature, many sudden rockfalls in these areas are recorded. Stabilizing and managing the entire area without localising potential threats would require considerable funding, which private owners and local communities cannot afford, so more suitable method for forecasting and detecting potential rockfalls is needed. For this study a specific location named Luka in Duće area is selected. Slope over Luka location is made of Eocene flysch, which is covered by a relatively thin and hard layer of breccia. Main component of flysch is marl, a rock material which is prone to weathering when submitted to atmospheric agents. As a result of weathering, surface formed of weaker marl is deteriorated and eroded with rain. A layer of a harder breccia remains and in time start to form "cantilevers" on the slope. With the development and elongation of joints in these "cantilevers", parts of breccia start to fall off in large blocks. LiDAR (Light Detection and Ranging) is an optical remote sensing technology used in Terrestrial Laser Scanners. TLS are often used to preform periodical monitoring in large landslide and rockfall areas. In this study Optech ILRIS-3D with enhanced range was used. Scanning was preformed from two scanning positions. The first position is located at the breakwater of a local marina that has a complete overview of the slope. The second position is located at the bottom of the slope which ranges as the shortest distance to the target area. Scanning from both positions was repeated in 3 months interval. In both cases first scan is georeferenced and it will be used as a reference scan for comparison of all future periodical monitoring at this location. Comparison of the two scans was made by using IM Survey module of Polyworks software and the results are presented in the article.

Breccia; Flysch; LiDAR; Spectrometer; Monitoring; Displacement detection; Rockfall

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