Disaster characteristics and mitigation of Chutigang gully debris flow, Mangkang county, Tibet
LU Ming, LIU Jinfeng
1. Key Laboratory of Mountain Hazards and Earth Surface Process, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, 610041, Chengdu, China; 2. University of Chinese Academy of Sciences, 100049, Beijing, China
Abstract:[Background] There were many debris flow gullies along the Mangkang county section of the Jinsha River. The frequent debris flow activities had destroyed the roads along the river, and even blocked the river to form a dammed lake, which seriously threatens the normal life of people in this area. In order to clearly understand the formation law and disaster-causing characteristics of debris flows in this area, this study selects the representative Chutigang gully as the research object, and we conducted detailed field investigation and analysis for providing theoretical reference for the prevention and control of debris flow disasters in this region. [Methods] In this study, the peak discharge of the latest debris flow was calculated by using the cross-section survey method:firstly, a typical channel section was selected, and its geometric parameters, channel longitudinal gradient and debris flow's mud mark high were measured, secondly these parameters were substituted into the Manning formula to complete the calculation. The outbreak scales of debris flows under different rainfall frequencies were calculated by using the rain-flood method, and the calculation results were substituted into two empirical formulas of river blocking to analyze the river blocking probability by debris flows under different rainfall frequencies. [Results] After field investigation, the solid source reserve of Chutigang gully was 625.1×104 m3, among which solid source of slope erosion was 576.8×104 m3. The peak discharge of the latest debris flow activity was 122.92 m3/s, and its outbreak scale was close to the magnitude of once in 50-year period. According to two empirical calculation formulas about river blocking by debris flow, it was known that when a debris flow with a magnitude of once in 100-year period, it may cause serious blockage of the river, and a once in 50-year period debris flow may cause minor blockages in the river. It should be alerted to the risk of debris flow blocking the main river to form a dammed lake. [Conclusions] According to the field investigation, most of the solid source of Chutigang gully was located in the middle and lower reaches of the watershed, which was prone to cause blockage-collapse phenomenon and expands the magnitude of debris flow. Based on the disaster characteristics of debris flow in Chutigang gully, a "Reinforcement+Blocking" disaster mitigation project was proposed, of which the check-dams group were mainly arranged in the middle and lower reaches of the watershed, they were used to reduce the accumulation of loose solid materials from both sides of the hillslope, and to reduce the probability of the channel being blocked. Silt-trap dam can reduce the debris flow peaks discharge and thereby mitigate the degree of erosion on the downstream channel. The treatment project can provide reference for the management of debris flow disasters in this region.
高云建,陈宁生,赵春瑶,等.干热河谷区泥石流活动特征及对交通干线的危害:以峨汉高速为例[J].人民长江, 2018, 49(10):54.GAO Yunjian, CHEN Ningsheng, ZHAO Chunyao, et al.Characteristics of debris flow activities in dry-hot valley and their impacts on major traffic arteries:A case study of E-Han Highway[J].Yangtze River, 2018, 49(10):54.
[4]
唐尧,王立娟,赵娟,等.遥感技术在"6·17"丹巴堵江泥石流灾害链灾区应急救援抢险决策中的应用[J].中国地质调查, 2020, 7(5):114.TANG Yao, WANG Lijuan, ZHAO Juan, et al.Application of remote sensing technology in emergency rescue decision about" 6·17"Danba River debris flow disaster chain[J].Geological Survey of China, 2020, 7(5):114.
[5]
唐川,黄润秋,黄达,等.金沙江美姑河牛牛坝水电站库区泥石流对工程影响分析[J].工程地质学报, 2006, 14(2):145.TANG Chuan, HUANG Runqiu, HUANG Da, et al.Impacts of debris flows on the reservoir of a hydropower station in the Meigu river of Jinshajiang[J].Journal of Engineering Geology, 2006, 14(2):145.
[6]
张金山,谢洪.岷江上游泥石流堵河可能性的经验公式判别[J].长江流域资源与环境, 2008, 17(4):651.ZHANG Jinshan, XIE Hong.Calculation of the possibility of river-blocking due to debris flow in the upper reaches of Minjiang river[J].Resources and Environment in the Yangtze Basin, 2008, 17(4):651.
[7]
中国地质调查局成都地质调查中心.四川省巴塘县地质灾害详细调查报告[R].成都,2009:23.China Geological Survey Chengdu Geological Survey Center.Detailed investigation report on geological disasters in Batang county, Sichuan province[R].Chengdu, 2009:23.
中华人民共和国国土资源部.泥石流灾害防治工程勘查规范:DZ/T 0220-2006[S].北京:中国标准出版社, 2006:26.Ministry of Land and Resources of the People's Republic of China.Specification of geological investigation for debris flow stabilization:DZ/T 0220-2006[S].Beijing:Standards Press of China, 2006:26.
[10]
蔡耀军,栾约生,杨启贵,等.金沙江白格堰塞体结构形态与溃决特征研究[J].人民长江, 2019, 50(3):15.CAI Yaojun, LUAN Yuesheng, YANG Qigui, et al.Study on structural morphology and dam-break characteristics ofBaige barrier dam on Jinsha river[J].Yangtze River, 2019, 50(3):15.