Detailed investigation of three-dimensional structure of wind-driven currents due to secondary circulations is needed to an accurate estimation of material transport on lakes and oceans. In this study, the convenient method to observe this structure by using the web camera, H-ADCP and Workhorse is proposed and the spatially-periodic profiles of horizontal wind-driven currents were obtained by using the method. Furthermore, surface velocities in the high-speed zones were estimated by applying the logarithmic law and the friction coefficient. From the results, the maximum surface velocity is about twice of 3.5% of U10, which is used in the general estimation of wind-driven surface currents.
