火后泥石流起动降雨阈值分析

王元欢; 沈昊文; 谢万银; 鲁科; 胡桂胜

doi:10.16031/j.cnki.issn.1003-8035.202208007

火后泥石流起动降雨阈值分析

doi: 10.16031/j.cnki.issn.1003-8035.202208007

王元欢^1,,
沈昊文^{2, 3, ,},
谢万银¹,
鲁科¹,
胡桂胜^{2, 4}

1.
四川省地质工程勘察院集团有限公司，四川成都　610072
2.
中国科学院、水利部成都山地灾害与环境研究所，四川成都　610041
3.
昆明理工大学，公共安全与应急管理学院，云南昆明　650093
4.
高原科学与可持续发展研究院，青海西宁　810016

基金项目: 第二次青藏高原综合科学考察研究项目（2019QZKK0902）、中国科学院青年创新促进会项目（2020367）、国家自然基金联合基金项目-小流域沟源凹槽土体滑坡形成泥石流的动力机制与灾害预判（U20A20110）

详细信息

作者简介:
王元欢（1985-），男，四川巴中人，本科，工程师，研究方向为岩土工程及地质灾害。E-mail：316919296@qq.com

通讯作者:
沈昊文（1995-），男，江西九江人，硕士研究生，研究方向为山地灾害形成机理与防治。E-mail：1756796469@qq.com

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出版历程
- 收稿日期: 2022-08-03
- 录用日期: 2023-04-17
- 修回日期: 2022-10-13
- 网络出版日期: 2023-04-26

Analysis of the rainfall threshold for post-fire debris flow initiation: A case study of the debris flow at Ren’eyong gully in Xiangcheng county, Sichuan province

Yuanhuan WANG^1
,,
Haowen SHEN^{2, 3
, ,},
Wanyin XIE¹,
Ke LU¹,
Guisheng HU^{2, 4}

1.
Sichuan Institute of Engineering Investigation, Chengdu Sichuan　610072, China
2.
Institute of Mountain Hazards and Environment, Chinese Academy of Sciences & Ministry of Water Conservancy, Chengdu Sichuan　610041, China
3.
Faculty of Public Safety and Emergency Management, Kunming University of Science and Technology, Kunming Yunnan　650093, China
4.
Academy of Plateau Science and Sustainability, Xining Qinghai　810016, China

摘要

摘要: 2014年初夏，中国西南中横断山区仁额拥沟遭受了一次森林大火，火后的短时低雨强在3#支沟内激发了3次泥石流；2015年8月的一次强降雨在仁额拥沟的1#、2#和3#支沟及其他附近的多个更小的流域内均激发了泥石流。为了解火后泥石流的降雨响应特征，本文采用距离修正的方式处理降雨数据，通过对4次泥石流发生的降雨过程分析，查明了流域特征对泥石流启动的作用及其对各支沟泥石流不同降雨阈值的影响。研究发现：1）泥石流降雨阈值在火后非常低且有随时间推移而增大的趋势；2）仁额拥沟火后泥石流具有高频率特征，其原因除了在于火后天然植被的破坏后降雨对坡面径流和侵蚀效应的放大，流域本身的性质也有极大的贡献；3）各支沟内泥石流降雨阈值差异的主要原因在于流域面积的差异，泥石流侵蚀受制于径流量大小。
- 火后泥石流 /
- 降雨阈值 /
- 距离修正 /
- 仁额拥沟 /
- 降雨响应
Abstract: In the early summer of 2014, a wildfire ravaged the Ren’eyong valley in the central Mt. Hengduan region of southwestern China. Following the blaze, debris flows were triggered three times in branch No. 3 due to short-term, low intensity rainfall. A year later, in August 2015, a brief period of high-intensity rainfall generated debris flows not only in branch No.3, but also in branch No. 1 and No. 2, as well as several smaller basins in the vicinity. To investigate the rainfall response characteristics of post-wildfire debris flow, the distance correction method was used to process the rainfall data. By analyzing the rainfall patterns of four debris flow events, the reseachers were able to identify the effects of watershed characteristics on the initiation of debris flow and its influence on different rainfall thresholds in each branch. The study found that: 1） Post fire debris flows can occur at a low rainfall threshold, which tends to increase over time. 2） The Ren’eyong valley experience high-frequency post fire debris flows, which can be attributed not only to the amplification of slope runoff and erosion caused by rainfall after the destruction of natural vegetation due to the wildfire, but also to the geological and geomorphic conditions of the area. 3） The rainfall threshold in each branch is primarily dependent on the drainage area, as the magnitude of discharge controls the entrainment.
- post-wildfire debris flow /
- rainfall threshold /
- distance correction /
- Reneyong valley /
- rainfall response

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图 1 研究区地理位置及相关信息

Figure 1. Location of the Ren’eyong Valley and related information of the study area

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图 2 区域地质纲要图

Figure 2. Outline Map of Regional Geology

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图 3 现场探槽照片

Figure 3. Site view of the on-site trenching

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图 4 被泥石流冲毁的房屋

Figure 4. Site photo of the ruined houses destroyed by debris flows

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图 5 泥石流发生时的降雨过程

Figure 5. Rainfall process during the debris flows

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图 6 3#支沟上游沟道

Figure 6. Site photo of the upstream channel at 3# branch ditch

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图 7 3#支沟下游沟道

Figure 7. Site photo of the downstream channel at 3# branch ditch

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图 8 1#支沟泥石流概貌

Figure 8. Overview of the debris flow at 1# branch ditch

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图 9 2#支沟泥石流概貌

Figure 9. Overview of the debris flow at 2# branch ditch

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图 10 非火烧区与火烧区坡积物对比

Figure 10. Comparison of slope sediments in non-fire area and fire areas

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图 11 火后泥石流携带坡面烧毁植被

Figure 11. Sie photo of the burned vegetation on post-fire debris flow carrying slope

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图 12 支沟泥石流冲刷侵蚀概况

Figure 12. Overview of debris flow erosion in the branch gully

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表 1 1#～3#支沟基本信息

Table 1. Geographic information of branches No.1～No.3

编号	流域面积/km²	沟长/m	平均坡度/（°）
1#支沟	0.37	544	27
2#支沟	0.73	755	26
3#支沟	2.30	836	15

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表 2 1#～3#支沟火烧强烈程度及面积统计

Table 2. Summary of fire severity classification and affected areas of branches No.1～No.3

编号	火烧面积/km²	轻度火烧/km²	中度火烧/km²
1#支沟	0.31	0.21	0.10
2#支沟	0.64	0.45	0.19
3#支沟	2.11	0.6	1.51

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表 3 泥石流基本情况

Table 3. Basic property information of the debris flows

序号	时间	位置	冲出量 /10⁴m³	前期3天降雨量/mm
DF1	2014年6月8日16:08	3#	0.8	1.11
DF2	2014年6月30日16:00	3#	1.4	14.84
DF3	2014年7月10日23:20	3#	0.5	0.81
DF4	2015年8月24日19:43	1#、2#、3#	2.2	39.97

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表 4 三处雨量站基本情况

Table 4. Summary of the basic property information of the three rain gauges

序号	名字	位置	海拔/m	距离/km	精度/mm	$ \omega_{i} $
1	正斗站	29°08′N,99°33′E	2858	4.10	0.1	0.577
2	热打站	29°06′N,99°38′E	3363	5.56	0.1	0.313
3	阿都站	29°11′N,99°39′E	2783	9.40	0.1	0.110

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