The branch block is a reinforced concrete block which consists of one trunk part and three branches part. In this study, basic hydraulic properties of the branch block bank protection were examined using the one-fortieth block model. Velocity measurements and flow visualization were carried out in a turbulent open channel flow in which the block models are set up along the side wall of the channel. The results of the velocity measurements show that the primary velocity over side wall is relatively low due to the strong secondary flow toward opposite side wall. Local low speed region were generated over the region of the junction of upper and lower branches of the block model. The results of flow visualization show that the large-scale longitudinal vortical structure is formed over the block model. It is inferred that these vortical structure contribute to generate characteristics of the velocity profiles.