Investigation and cause analysis of the debris flow in Shuiquangou watershed of Zhouqu County

In order to explore the formation cause of the debris flow in Zhouqu County of Gansu Province, and protect the safety of people's lives and property, the authors took the detris flow in Shuiquangou watershed of Zhouqu County as the research object. The regional survey, ground investigation and underground exploration methods were used to ascertain the characteristics of debris flow and analyze its formation cause, on the basis of geological environment conditions investigation and analyzation in the study area. Besides, the dangerous area of the debris flow was divided. The results show that the loose slope structure and steep slope could induce debris flow under the action of precipitation, earthquake, engineering activity or gravity. The design gravity of the debris flow in Shuiquangou is 18.7 kN/m³, and the annual discharge is 1.24×10⁴ m³/a. The maximum discharge of the debris flow is 0.66×10⁴ m³ and the maximum pressure of the debris flow is 190.22 kN, with maximum climbing height of 6.2 m. Extreme dangerous area is distributed from Shuiquangou estuary to Bailongjiang river bank, with the area of 0.13 km², accounting for 9.8% of the total area, which has worst effects on Shuiquanxincun, 313 provincial road and Fengdie area. It is suggested that two gravity-grouted Shigufang dams should be arranged in the middle and lower reaches of the main ditch, and one should be arranged in the alluvial fan ditch, with a 894-meter-long drainage dam. This research could provide some reference for the debris flow prevention in Gansu Province.