Abstract
An image-based field measurement method of river flow was applied to a large flood that occurred in the Ibo River and the measurement results were compared with those calculated by two and three dimensional numerical simulation models for evaluating the accuracy of simulations. The target river site has a large bend with a cobble bar on its right in the mid reach of the river. Flow measurements were conducted by taking video images of flood surface flows; i.e. streamwise surface velocity distributions were obtained by the space-time image velocimetry (STIV). It was confirmed from the comparison of velocity distributions at some sections, simulation parameters need some modifications that takes into account of a number of large rocks located near the outer bank. Improvement of simulation accuracy was established by providing direct measurement data by STIV.
