[HGM03-P06] Elevation change in a river park flooded by the typhoon Hagibis in 2019
Keywords:River, Typhoon Hagibis, UAV
Five hundred and eighty three photo images were obtained with a UAV (Phantom 4 ver.2, DJI) flying at a height of 50 m on November 28, 2019. In addition, the latitude & longitude and the altitude of eleven ground-control-points (GCPs) were measured with a differential GPS receiver (GIR1600, Sokkia) and an auto level (AP-8, Nikon), respectively. Using the above data, a 50 cm-digital surface model (DSM) was created with a MfS software, Agisoft photoscan 1.4.5.
Five survey lines were set in the observation area, and comparison was conducted between the cross sections of the 50 cm-DSM obtained in the present study and a 1 m-digital elevation model (DEM) based on the laser survey performed by Geographical Survey Institute in 2012. At the left bank of the Niida River, the edge of the river park was greatly eroded up to 26 m horizontally, while new gravels were deposited near the right bank.