Effects of the groves against flood hazards on dyke breach flows and the hydrodynamic forces acting on a structure are investigated experimentally. It is found that depending on Froude number at the broken point of the embankment, characteristics (size of tree, density and length of forest zone) of the groves and the distance of groves from the broken point, different type of the flows, namely, submerged outflow,forced hydraulic jump and jump-spray are observed. The regime of the flows is distinguished by the ratio of specific force of the flows to retarding force due to the groves. It is also found that the primary mechanism for reduction of the hydrodynamic forces acting on a structure is due to increase of flow depth downstream of the groves.
