Articles | Volume 17, issue 9
Research article
13 Sep 2017
Research article |  | 13 Sep 2017

Application of UAV-SfM photogrammetry and aerial lidar to a disastrous flood: repeated topographic measurement of a newly formed crevasse splay of the Kinu River, central Japan

Atsuto Izumida, Shoichiro Uchiyama, and Toshihiko Sugai

Abstract. Geomorphic impacts of a disastrous crevasse splay that formed in September 2015 and its post-formation modifications were quantitatively documented by using repeated, high-definition digital surface models (DSMs) of an inhabited and cultivated floodplain of the Kinu River, central Japan. The DSMs were based on pre-flood (resolution: 2 m) and post-flood (resolution: 1 m) aerial light detection and ranging (lidar) data from January 2007 and September 2015, respectively, and on structure-from-motion (SfM) photogrammetry data (resolution: 3.84 cm) derived from aerial photos taken by an unmanned aerial vehicle (UAV) in December 2015. After elimination of systematic errors among the DSMs and down-sampling of the SfM-derived DSM, elevation changes on the order of 10−1 m – including not only topography but also growth of vegetation, vanishing of flood waters, and restoration and repair works – were detected. Comparison of the DSMs showed that the volume eroded by the flood was more than twice the deposited volume in the area within 300–500 m of the breached artificial levee, where the topography was significantly affected. The results suggest that DSMs based on a combination of UAV-SfM and lidar data can be used to quantify, rapidly and in rich detail, topographic changes on floodplains caused by floods.

Short summary
Geomorphic impact of the 2015 flood of the Kinu River, which created a new crevasse splay on its floodplain, was quantified by volumetric calculations using three topographic data obtained by aerial laser scanning (ALS) and UAV photogrammetry. Topographic changes on the order of 0.1 m were detected, and the erosive character of the crevasse splay was revealed. The results suggest that a combination of ALS and UAV is useful for quantification of sudden topographic changes through disasters.
Final-revised paper