Bed scouring protective works with concrete blocks are installed on the downstream bed of hydraulic structures. The bed scouting around bed protective works decreases the stability of the last row block of the structure. Additionally, the hydrodynamic force acting on the last row block is larger than that of any other blocks of its group. So, the last row block is a weak point in the bed protective works. However, the design method for the downstream area of bed protective works is not established because it is difficult to estimate the flow and bed variation there.
In this paper, two-dimensional numerical model for the flow over hydraulic structures, which employs the moving grid system in vertical direction, is developed. The model can calculate hydrodynamic forces acting on the last row blocks of its group, and applicable to simulate the flow in the downstream of two-dimensional hydraulic structures.