因缺乏修筑溢洪道的地形条件或修筑溢洪道耗资过大而暂不能修筑溢洪道时，最好能设置放水建筑物。放水建筑物的泄量，以能渲泄坝系形成后该坝所控制的区间集流面积内二十年一遇的洪峰为最好。设计淤地坝工程时，其溢洪道和放在建筑物的位置，最好能发置在背阴坡面上，以备坝地 Due to the lack of topographical conditions for the construction of spillways or the excessive cost of building spillways, spillways can not be constructed temporarily, so it is best to set up drainage structures. Drainage of water discharge structures, to be able to rendezvous dam formed after the formation of the dam control area within a catchment area within a peak of 20 years as the best flood peak. When designing silt dam project, the spillway and the place on the building should be set up on the slope of the slope to prepare for dam site