IMPACT ASSESSMENT OF A LAGRE FLOOD ON RIPARIAN VEGETATION IN KINUGAWA RIVER CHANNELS BY USING UAV MEASUREMENT

Abstract

 This paper examined a large flood impact on riparian vegetation in Kinugawa River channels observed by an unmanned aerial vehicle (UAV). The flood occurred on September 9-10, 2015 owing to the heavy rainfall that brought tremendous volume of water on the Kanto and Tohoku regions of Japan. In order to investigate the very initial state of the after-flood-impact throughout Kinugawa channel network, 13 channel sections with 2.3 km each in longitudinal length were chosen and observed in October, 2015. The results with the geographic information system (GIS) analysis and hydraulic model simulation show that the river sections in the most upstream segment indicated severe damage of trees and herbs as well as large movement of gravel bed material. Furthermore, relationships between the vegetation damages, bed shear stresses, and drag forces calculated by the hydraulic model simulation were discussed along the river channel networks.