engleski

DETECTION OF SPATIO-TEMPORAL CHANGES CAUSED BY GULLY EROSION USING THE REPEAT UAV PHOTOGRAMMETRY

Study of various spatio-temporal changes caused by gully erosion is the basis for better understanding of gully erosion intensity, impacts and mechanisms. In this research we present the results and difficulties of monitoring and detection of these spatio- temporal changes using the repeat unmanned aerial vehicle (UAV) photogrammetry. Research was carried out at gully Satniš, located at Pag Island (Croatia), where traces of recent intensive erosion have been observed. Repeat UAV photogrammetry is emerging as time and cost efficient method that allows accurate aerial surveying of complex terrain features, such as gullies. Complex topography of gully Santiš (e.g. overhangs in headwall) pointed to certain advantages and shortcomings of UAV photogrammetry, that are explained in this paper. Assessment of UAV photogrammetry reliability and quality was based on comparison of acquired data with terrestrial LiDAR survey. Detection of spatio-temporal changes was performed based on comparison of two sequential high-resolution digital surface models (DSMs). DSMs were created from aerial photographs captured by DJI Phantom 4, where first aerial survey was conducted on May 26, 2017, and second one on November 20, 2017. In total around 350 aerial photographs were acquired on each aerial survey that were later processed in Agisoft Photoscan PRO software. With spatial resolution of 2 cm created DSMs allowed detailed detection and quantification of spatio-temporal changes that have occurred within gully. Detected erosion intensity varied from few centimetres to even few decimetres, while most intense erosion was registered at gully headwall. Repeat UAV photogrammetry proved to be a reliable and simple method for gully erosion monitoring.

gully erosion, UAV photogrammetry, spatio-temporal changes, Pag Island

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