Lessons from Catastrophic Dam Failures in August 1975 in Zhumadian, China

Abstract

During 4–8 August 1975, an extreme storm occurred in Henan Province, China. The maximum 5-day rainfall reached a record of 1,631 mm. Two large dams (Banqiao Dam and Shimandan Dam), two medium dams (Tiangang Dam and Zhugou Dam), and 58 small dams failed from overtopping in the storm event. The breach peak flow rate was as high as 78,100 m3/s from the Banqiao reservoir and 30,000 m3/s from the Shimantan reservoir. The breaching of these dams caused an inundated area of 12,000 km2, a death toll of over 26,000, and economic loss of more than RMB10 billion. This paper introduces 26 dam failures in a smaller region of Zhumadian, i.e., Banqiao Dam, Zhugou Dam, and 24 small dams. The catastrophic event is described in detail especially for Banqiao Dam and Zhugou Dam. The causes and mechanisms of the principal failures are discussed, as well as the influence of an upstream dam failure on the downstream dams. Lessons from the catastrophe are discussed.