黄土高原不同土地利用类型区浅层滑坡侵蚀特征分析——以蔡家川滑坡事件为例

doi:10.13866/j.azr.2024.04.15

摘要/Abstract

摘要：

近年来，黄土高原极端暴雨引发的滑坡、泥流等剧烈水土流失引起了广泛关注。2021年10月3—6日，山西省吉县蔡家川一带强降雨诱发了大面积浅层滑坡灾害。本文利用灾前灾后无人机影像和遥感图像、降雨数据及现场调查数据，对本次降雨过程、浅层滑坡起动条件和侵蚀特征进行了分析。结果表明：本次降雨为典型的“长历时、低雨强”类型，滑坡发生前的前期降雨历时达72 h，累积雨量达121.8 mm，滑坡集中发生时段的雨强达33.2 mm·(6h)^-1。与“短历时、高雨强”暴雨激发的滑坡相比，滑坡流动性相对较高。前期降雨是影响群发性滑坡灾害发生与流动性的重要因素。不同土地利用类型区滑坡起动地形条件差异显著，所需坡度与汇水面积均表现为：封禁林区>人工林区>农地区；地层岩性的渗透性也影响着浅层滑坡的起动，相同降雨量条件下，渗透性更好的林区发生浅层滑坡需要更高的面积坡度阈值。不同土地利用类型区，滑坡点密度、面密度与侵蚀强度的大小均表现为：农地区>人工林区>封禁林区，说明土地利用类型会在一定程度上影响滑坡的侵蚀程度，以乔木为主的林区更不利于滑坡发生。

关键词: 极端暴雨, 植被恢复, 浅层滑坡, 黄土高原

Abstract:

In recent years, drastic and extreme forms of soil erosion, such as landslides, mudflows, and silt dam outbursts, triggered by extreme rainstorms on the Loess Plateau have attracted widespread attention. From October 3 to 6, 2021, a large shallow landslide disaster was triggered by heavy rainfall along the Caijiachuan watershed in Jixian County, Shanxi Province. In this study, the rainfall process, landslide initiation conditions, and erosion characteristics were analyzed using predisaster and postdisaster unmanned aerial vehicle imagery, historical remote sensing images, and rainfall data provided by the National Field Scientific Observatory for Forest Ecosystems in Jixian County, Shanxi Province. The results show that it was a typical “long-duration, low-intensity” rainfall, with a total precipitation of 121.8 mm in the first 72 h of the initiation of the massive, shallow landslides and a rainfall intensity of 33.2 mm·(6h)^-1 during the initiation of the landslides. The landslide triggered by this rainstorm required a slightly smaller catchment area and exhibited higher landslide mobility than the landslide triggered by a typical short-duration, high-intensity rainstorm in 2003; however, the slope of the landslide was not significantly different. Thus, the cumulative rainfall in the early stage was the main factor influencing the occurrence and flexibility of the massive landslide disaster. The magnitude of landslide number probability, area probability, and erosion intensity in catchments with different land use types decreased in the following order: farmland catchment>plantation forest catchment>closed catchment. This finding indicated that the land use type and vegetation cover affect the degree of landslide erosion to a certain extent and that an arboreal-dominated watershed is more unfavorable to landslide initiation.

Key words: extreme rainstorm, vegetation recovery, shallow landslides, Loess Plateau

王鑫盈, 马超, 吕立群, 张岩. 黄土高原不同土地利用类型区浅层滑坡侵蚀特征分析——以蔡家川滑坡事件为例[J]. 干旱区研究, 2024, 41(4): 697-705.

WANG Xinying, MA Chao, LYU Liqun, ZHANG Yan. Erosion characteristics of shallow landslides under various land-use conditions: An example of the Caijiachuan landslide[J]. Arid Zone Research, 2024, 41(4): 697-705.

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时代	层底深度/m	分层厚度/m	岩土名称及特征
Q₄	0~0.6	0~0.6	耕土：黄褐色，稍湿，稍密，以粉土为主，土质不均匀，结构疏松
Q_p	1.0~1.6	1.0	粉土：黄褐色，稍湿，稍密，土质均匀，粉质一般，无光泽，干强度低，韧性低，局部夹有卵砾石
Q_p	2.5~3.1	1.5	卵石：杂色，中密，稍湿，分选性差，磨圆度较好，主要成分为泥岩，含有砾石，中等风化，粒径一般为3.0~7.0 cm，最大约为15 cm，含量约为56%，以圆形及亚圆形为主，充填物主为粉土
T	9.4~10.0	6.9	泥岩：红褐色，泥质结构，具层理，块状构造，具裂隙，中等风化，岩芯较破碎，呈碎块状、短柱状，裂隙充填物为砂土
T	10.9~11.5	1.5	砂岩：褐红色，细粒结构，块状构造，中等风化，主要矿物成份为长石、石英，钙质胶结，岩石为硬质岩石，裂隙节理发育，岩芯呈长柱状

土地利用类型	封禁林区	农地区	人工林区
流域面积/km²	1.932	0.7	1.536
流域（坡度>25°）面积/km²	1.181	0.368	1.098
滑坡数量/个	97	220	171
LNP/(个·km^-2)	82	597	156
滑坡面积/m²	25856	34512	38697
单个滑坡面积平均/m²	267	157	226
单个滑坡面积最大/m²	1101	1051	1466
单个滑坡面积最小/m²	28.8	9.6	12.5
LAP/(m²·m^-2)	2.19×10^-2	9.37×10^-2	3.52×10^-2
侵蚀量/m³	21976	21747	31335
侵蚀强度/(m³·m^-2)	1.86×10^-2	5.91×10^-2	2.85×10^-2