UAV Photogrammetry for Monitoring Changes in River Topography and Vegetation

This study aims to evaluate the accuracy of digital surface model (DSM) of river-channel morphology, which is derived from the imagery acquired with a low-cost digital camera on board an unmanned multi-copter. UAV photogrammetry at flight altitude of 100 m has been carried out before and after a man-made flood in the Jyoge River in Hiroshima Prefecture, Japan along with ground survey using RTK-GPS and Total Station. The UAV photogrammetry has demonstrated that the DSM reproduces the ground elevation very well with the maximum error of 4 cm over a floodway where the vegetation height and density are low and that the DSM reasonably captures the thick vegetation cover over sandbars. It is also confirmed that the difference in DSM before and after the flood is due to the plant toppling over sandbars.