Abstract
This paper presents a simple estimation method of hydraulic structure in a fan-shaped fishway, based on the field observation on the fishway installed at Kuranomachi Weir in Ono River in Matsuyama, Ehime, Japan. The flow regime in the pools of the fishway was a plunging flow with discharge ranging from 200l/s to 350l/s. The estimation procedure, given the discharge, is as follows: 1) Estimate the water depth on the notch of the baffle, 2) Estimate the flow velocity on the notch using the estimated water depth, and 3) Estimate the magnitude of the velocity distributed in the pool downstream of the notch using the estimated flow velocity on the notch. A maximum velocity in the pool, approximately 1.75 times the velocity on the notch, is estimated at the plunging point.