Submerged closure dams are often used in channel regulation projects to adjust the diversion ratio of branches，and the structure is generally composed of the dam body and the bottom protection mattress.Since the submerged closure dam crosses the branch of deep water with high flow velocity，it has an obvious regulating effect on water flow and can easily cause local violent scouring of the riverbed，and the changes in the riverbed react on the building structure，thus leading to local deformation and even damage.This paper selects two submerged closure dams in the left branch of Hechangzhou Waterway as a typical case and analyzes the effects of building implementation，as well as the deformation and local damage of the building by using measured data combined with water flow simulation analysis.Then，the paper discusses the characteristics and causes of local damage.The results show that the dam body is basically intact，and the deformation mainly occurs at the edge of the bottom protection mattress；the damaged area of the mattress corresponds to the location where the intense scouring occurs near the buildings.The main causes of damage are the mainstream scouring of the deep channel in the waterway during the flooding period，the turbulent scouring of the downstream water flow in the slope change area of the dam body，and the accelerated damage of the mattress during the long period of flooding in special hydrological years.