不同植被防护措施对三峡库区土质道路边坡侵蚀的影响

道路建设形成的大量裸露边坡缺乏防护常常导致严重的水土流失,是山区流域重要的侵蚀源.本文以三峡库区新修土质道路边坡为研究对象,布设草本、草灌结合、草灌+梯坎组合、植生带、坡耕地、草本+坡耕地组合进行边坡防护,结合野外自然降雨观测,研究降雨及植被防护对边坡侵蚀的影响.结果表明:草灌结合措施的植被恢复速度最快,平均盖度由20.2％增加到91.6％,对土壤容重和导水率改善最明显,降低容重9.5％,增加导水率678.1％,其次是草本措施和植生带;梯坎+草灌结合的抗侵蚀能力最强,截流效率和阻沙效率分别为72.3％和80.2％,适用于坡度＞45°路堑,其次是草灌结合和草本,草本对路堤的防护效果高于路堑,草灌结合对路堑的防护效果更理想;在15°缓坡路堤,草本+坡耕地处理对径流的拦截效率很低,仅2.0％,但拦截泥沙效率与草本和草灌相当,为23.0％,当坡度＜15°路堤被用作耕地时,必须在路肩设置2 m长的草本缓冲带以满足侵蚀防护的要求.

Effects of different vegetation protection measures on erosion prevention of unpaved roadside slopes in Three Gorges Reservoir Area

One of the main impacts of road construction is the creation of bare and steep slopes when lack of vegetation protection, which usually generates serious soil loss, a major erosion source in mountainous areas. In this study, six treatments including planting grass (GRA), grass and bush (GBC), building terrace combined with grass and bush (TGB), planting sod strip (SS), building sloping farmland (SFL), and building sloping farmland combined with grass (SFLG) were installed on the newly constructed unpaved roadside slopes in Three Gorges Reservoir Area to investigate the effects of these measures on the erosion prevention of the unpaved roadside slopes under natural rainfall. Among the six treatments, GBC had the best effect, which had the quickest revegetation rate (the mean vegetation coverage increased from 20.2% to 91.6%), decreased the soil bulk density by 9.5%, and increased the saturated hydraulic conductivity by 678.1%, followed by GRA and SS. TGB had the greatest potential in mitigating soil loss and runoff, with the efficiency in trapping sediment and runoff reached 80.2% and 72.3%, respectively, being appropriate for the cut slopes with a gradient greater than 45 degrees, followed by GBC and GRA. GRA had a higher efficiency on fill slope than on cut slope, while GBC showed greater applicability on cut slope. On the fill slope with a moderate gradient 15 degrees, SFLG had a potential of trapping 23.0% of sediment, which was equivalent to that of GRA and GBC, but the efficiency in trapping runoff was only 2.0%. When the fill slopes with a gradient less than 15 degrees were utilized as farmland, a grass buffer strip of 2 m length was needed on the upslope for erosion control.