Debris flow hazard assessment at Dongmatun Village in Laomao mountainous area of Dalian, Northeast China
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ORIGINAL PAPER
Debris flow hazard assessment at Dongmatun Village in Laomao mountainous area of Dalian, Northeast China Shiwei Shen 1,2 & Wenwang Liao 1 & Lei Nie 1 & Yan Xu 1 & Min Zhang 1 Received: 30 August 2017 / Accepted: 27 September 2018 # Saudi Society for Geosciences 2018
Abstract After a heavy and continuous rainfall from July 27 to 28, 1981, geological disasters involving large debris flow affected the northern part of Wafangdian City and Pulandian City in Dalian, northeast China, and caused considerable loss of life and property. In recent years, precipitation has continued to increase significantly in Dalian, where the largest debris flow gully, named the Dongmatuncun main ditch, is situated. The Dongmatuncun main ditch is 2 km away from the north side of the right bank of the Fudu River in Wanjialing, Wafangdian City. The geomorphological and hydrological conditions, combined with the characteristics of the debris flow solid source, are conducive to debris flow development. Moreover, with an increase in rainfall, debris flow recurrence becomes increasingly likely. We study the debris flow gully in Dongmatun Village by analyzing the formation conditions through field survey. Fuzzy comprehensive evaluation and analytic hierarchy process are used to evaluate the risk of debris flow. Results indicate that the debris flow gully in Dongmatun Village is highly dangerous and debris flow occurs during heavy rainfall. In addition, the breakout of debris flow can threaten human life and property. Keywords Dongmatuncun main ditch . Debris flow formation condition . AHP–fuzzy comprehensive evaluation . Risk assessment
Introduction Debris flows are a great danger for human settlements in mountain regions around the world (Rybchenko et al. 2018; Tiranti et al. 2014; Lo et al. 2012). They occur when masses of poorly sorted sediment, agitated and saturated with water, surge down slopes in response to gravitational attraction (Iverson 1997). Their high flow velocity, force of impact, and long runout, combined with poor temporal predictability, make debris flows and debris avalanches one of the most hazardous landslide types (Wang et al. 2016; Jakob and Hungr 2005). From July 27 to 28, 1981, a heavy rainfall of between 200 and 650 mm occurred in the Laomao mountainous area, at the
* Shiwei Shen [email protected] 1
College of Construction Engineering, Jilin University, Changchun 130026, Jilin, China
2
State Key Laboratory of Frozen Soil Engineering, Chinese Academy of Sciences, Lanzhou 730000, Gansu, China
junction of Xinjin and Fuxian Counties, due to the combination of Typhoon No. 8018 and westerlies. The storm was fierce, and the rainfall was continuous. Heavy rainfall constantly poured for 5 h, starting at 23:00 on July 27 and ending at 04:00 on July 28. The average rainfall was 50–60 mm/h. The heavy rain affected a small area; the central region was significantly damaged. The average rainfall measurements on the peak of Laomao Mountain were 600–750 mm. Landslide occurred in many places in Laomao due to the
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