ABSTRACT
Field measurement by tracking the floats is usually conducted to estimate flood discharge in rivers. It is assumed that the movement of floats is associated with flow velocity on water surface. The estimated surface velocity is multiplied with some correction factor so that the cross-sectional mean velocity and discharge are estimated. In order to estimate the accuracy of float flow measurement, 3D flow analyses were conducted. The observed mean velocity was compared with the result of 3D flow analysis for the accuracy of mean velocity estimation from float flow measurement.
