三工河小流域泥石流生态—岩土工程调控措施减缓土壤侵蚀的定量研究

Quantitative study on the mitigation of soil erosion by comprehensive ecological and geotechnical debris flow treatment measures in small basins:A case study of the Sangong River Basin

为探讨泥石流治理措施对小流域土壤侵蚀的影响,以天池上游三工河流域为研究对象,在实地考察的基础上,通过地形图叠加、遥感解译和Google Earth Engine(GEE)云计算等手段,实测计算了该流域1971~2003年、2008~2020年两期土壤侵蚀模数,定量评估了在该流域开展的泥石流生态—岩土工程调控措施对小流域生态和土壤侵蚀的影响。研究发现:(1)三工河流域平均植被覆盖度经泥石流综合治理后增加11.34%,高植被覆盖度面积增加16.93%,泥石流沟道及河谷的植被覆盖度明显提升;(2)三工河流域1971~2003年平均侵蚀模数为0.34 mm/a,较北天山山地流域同期平均侵蚀速率高出131%,造成该现象的原因是过度放牧、滥砍滥伐等人为因素激发山洪泥石流的爆发导致流域生态环境恶化;(3)流域经生态—岩土工程调控后(2008~2020年),平均侵蚀模数降低至治理前的15%(0.051 mm/a),为北天山地区山地流域同期平均侵蚀模数的34%。

In order to assess quantitatively the impact of debris flow control projects on soil erosion in small basins,this paper takes the Sangong River Basin in the upper reaches of Tianchi Lake as the research object.Based on field investigation data,a topographic map overlay,and remote sensing interpretation data,we calculate the soil erosion rate of the basin in two periods(1971~2003 and 2008~2020).We also use Google Earth Engine to compute the change of vegetation coverage in this basin over the study years,the impact of comprehensive ecological and geotechnical debris flow treatment measures carried out in this scenic spot on the soil erosion and ecology of the basin are thus uncovered.Our main results were:(1)the average vegetation cover of Sangong River Basin increased by 11.34%after the debris flow treatment,where areas with high vegetation cover increased by 16.93%,and the vegetation cover of the debris flow gullies and river valleys increased significantly.(2)The average erosion rate of Sangong River Basin from 1971 to 2003 was 0.34 mm/a,which was 131%higher than the average erosion rate of the North Tianshan Mountain Basin in the same period.This erosion rate was caused by deterioration of basin ecology due to the outbreak of flash floods and debris flows triggered by human factors such as overgrazing and indiscriminate logging.(3)After the basin was regulated by ecological and geotechnical engineering projects(2008~2020),the average erosion rate reduced to 15%(0.051 mm/a)of that before treatment,which was only 34%of the average erosion rate of the same period in the mountain basin of the North Tianshan region.