Abstract
This paper reports the application of a PTV-technique to the measurement of flow velocity in the open-channel with vegetation. The features on the local hydraulic characteristics of flows around the vegetative groins are discussed through the hydraulic experiments. It is shown that the vegetative groin work, which was made of vegetation as a part of river training works, has the basic function as groin work on reducing the velocity inside the groin region and on splashing water toward the main flow. The effects on splashing water and reducing the velocity depend on vegetative compactness. Consequently, the present vegetative groin work seems to function well as habitats for the aquatic life, because the areas of low flow velocity are formed inside the groin region, which shifts locally with change of the vegetative compactness of groin and its angle.
