Dam-break flood risk assessment and mitigation measures for the Hongshiyan landslide-dammed lake triggered by the 2014 Ludian earthquake

Landslide-dammed lake is a typical geological hazard induced by earthquakes in mountainous river areas that pose a great threat to human lives and property for reservoirs and downstream areas. In this paper, the 3 August 2014, Hongshiyan landslide-dammed lake induced by the Ludian earthquake (Mw 6.5) was taken as an example to study the dam-break risk and flood routing process. The fuzzy mathematics method was used to evaluate the risk level of the Hongshiyan landslide-dammed lake, and six main indicators were developed to classify its risk level. The assessment results indicated that the Hongshiyan landslide-dammed lake had an extremely high risk and very serious possible disaster consequences. Then, we analyzed the possible dam-break flood routing process by numerical simulation. The simulated results showed that a dam-break flood would pose a great threat to the downstream Tianhuaban Hydropower Station. Therefore, some effective artificial measures must be taken to control the scale of the disaster. The artificial measures included upstream interception, middle grooming, downstream emissions and subsequent treatments. Some emergency measures were implemented and prevented the failure of the landslide-dammed lake through 19:00, October 4 2014, and subsequent treatment even turned the potential harm into a benefit.