STIV ANALYSIS OF FLOOD DISCHARGE AT NAKANO OBSERVATORY IN THE OTA RIVER AND ITS VERIFICATION BY FLOW ANALYSIS USING ALB DATA

Abstract

 Non-contact type of measurement methods with support of cost-efficient devices and improved algorithms for flow analysis have been actively developed for river discharge observations during flooding. These updated methods are expected to be used widely in practical works for both river channel planning and disaster reduction. We conducted flow measurements using a space-time image velocimetry (STIV) method at Nakano Observatory in the Ota River during the heavy rainfall in July 2018. Results showed that the discharge values obtained every hour using the existing H-Q rating curve were overestimated by approximately 10 percent, compared with those using the present STIV method.

 This study aims at examining the accuracy of the present STIV method for river discharge estimation during the flood, using numerical simulation results and water level observations. First, we obtained the data for both the topo-bathymetry and vegetation properties within a targeted reach by airborne laser bathymetry (ALB) measurement results. Secondly, we conducted numerical simulations of the flood flows using the discharge hydrograph of two kinds: the rating curve and the STIV method. Lastly, we compared simulated water levels with observations during the flood. Results demonstrated that the STIV method provided more accurate discharges, compared with the rating curve.