SPATIAL MEASUREMENTS OF SNOW MELT FLOOD BY IMAGE ANALYSIS WITH MULTIPLE-ANGLE IMAGES AND RADIO-CONTROLLED ADCP

Abstract

Measurements of flood flow have been conducted intensively at major control sections in Japan for storing reliable hydrological data to use for a long-term river planning. However, such a measurement pays attention only on a flow passing through one cross-section and thus spatial flow features are not available, while river channel changes its feature at every flood event. In this research, we performed concurrent measurements of a snowmelt flood of the Uono River by an image analysis and a radio-controlled ADCP. In the image analysis with STIV (Space-time Image Velocimetry), three video cameras were used to cover a river reach of about 500m by changing their view angles at every location. On the other hand, the boat-mounted ADCP was remotely controlled to form a zigzag trajectory to cover the same reach. The accuracy and limitation of STIV was made clear through a comparison with ADCP data and a spatial distribution of correction factor from surface to depth-averaged velocity was found to have a weak correlation with a large-scale bed slope.