Draining Tangjiashan Barrier Lake after Wenchuan Earthquake and the flood propagation after the dam break

Tangjiashan Barrier Lake is one of the largest barrier lakes caused by the Wenchuan Earthquake. Its risk analysis, emergency plan and effect of the emergency plan are introduced in this paper. The dam height of Tangjiashan Barrier Dam is about 105 m, and the reservoir storage capacity is 3.2×10⁸ m³. When the dam broke the flood peak were estimated to be larger than 48000 m³/s, which might cause a enormous disaster to the downstream cities and residents. A discharge channel with 13 m deep and 8 m wide was drug, so that the water may flow out of the lake before the dam breaks. As a result, the drainage and risk mitigation project are successful. During the drainage process, the flood peak was about 6500 m³/s, and about 1.6×10⁸ m³ of water was drained off and the residual reservoir capacity was only 8.97×10⁷ m³. A new channel with average width 100 m was formed, which can bear floods of 200 years frequency. The successful experience and the collected data can be used to deal with the similar natural disasters in future. Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2007CB714102)