Abstract
After the Dainichigawa dam construction gravel supply to downstream from the dam site decreased in the Tedori River. As a result, river bed degradation progressed and gravel bed area gradually decreased. Furthermore, exposure of soft rock remarkably progressed around 14km to 15km from the river mouth. The exposure of soft rock not only endangers hydraulic structures but also deteriorates river environment. Therefore, gravel bed restoration works using groin group composed of connected stones were carried out. After the groins installation, parts of the groin were deformed during the flood in 2011. This paper aims to clarify the deformation mechanism of them using two-dimensional flow analysis. Numerical results showed that the hydrodynamic force acting on the groin caused by high velocity surpassing its design transformed the parts of the groin.
