Disaster mechanism of post-fire debris flow in Huayanzi gully, Mianning County, Sichuan Province
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摘要:
以四川省冕宁县腊窝乡华岩子沟2019年7月发生的火后泥石流为典型案例,通过对火烧迹地现场地质勘察、降雨模拟试验研究了与火后泥石流形成相关的地形地貌、火行为分布、松散物源规模、产流产沙特征以及相应的灰烬层、斥水性、渗透性等相关试验。结果表明:(1)火烧迹地的斥水性强度越强,径流产流量越大;(2)严重火烧区的产沙量明显高于中度和轻度火烧区;(3)火烧迹地的斥水性与火烈度大致呈正相关,而渗透性恰好与之相反。研究揭示了火后泥石流的演变过程,为火后泥石流的防治和预警提供了理论依据。
Abstract:This paper studied the characteristics of geomorphology, fire behavior, unconsolidated source material volume, runoff and sediment production related to post-fire debris flow formations, field investigation in the burned area and rainfall simulation experiment were adopted to study the post-fire debris flow in Huayanzi gully, Mianning County, Sichuan Province occurred on 4 July 2019. The associated ash layer, water repellency and permeability experiments were also conducted. The results suggest that (1) the runoff charge shows a positive correlation with water repellency in burned area. (2) the sediment yields in severely burned area are conspicuously larger than that in moderate and slight burned areas. (3) the water repellency in burned area is approximately positively correlated with fire severity, while the permeability presents the negative correlation. This study revealed the evolution process of post-fire debris flow, and provided theoretical basis for the prevention and early warning of post-fire debris flows.
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表 1 火烈度划分标准
Table 1. Fire severity classification standard
依据火烈度 地面覆盖物过火情况 树干(枝)烧黑高度 树叶烧毁情况 未火烧 未过火 未烧黑 绿色 轻度 地面草,落叶过火;
草桩,腐殖质层保留树枝未烧到,
树干烧黑小于3 m树叶基本绿色 中度 地面草,落叶,
半腐殖质层基本烧毁树干烧黑高度
5~10 m,树梢保留树叶多为黄色,
少数黑色重度 地面草,落叶,
半腐殖质层全部烧毁树干烧黑高度
大于10 m,或
全黑或树桩烧断树叶烧毁或保
留全黑树梢 -
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