典型泥石流小流域降雨和土地利用对坡面侵蚀的影响

Effects of Rainfall and Land Use on Slope Erosion in Typical Debris Flow Small Watershed

[目的]揭示泥石流小流域降雨和土地利用对流域内坡面侵蚀的影响和作用,为泥石流的生态治理提供科学依据。[方法]以白龙江流域一级支沟——甘家沟泥石流小流域为研究区,基于该流域已建的5个径流小区(裸地、坡耕地、草地、土坎梯田、经济林地)连续5年的观测资料,利用K-均值聚类法,选择降雨量(P)、降雨历时(D)和最大30 min降雨强度(I30)3个降雨指标,将该流域46次侵蚀性降雨事件划分为3类雨型(Ⅰ型、Ⅱ型、Ⅲ型),以平均径流系数和平均土壤流失量为主要指标,定量化分析了不同降雨雨型和土地利用类型对坡面产流产沙的影响和作用。[结果]径流和土壤流失对降雨的响应存在差异,平均径流系数为Ⅰ型降雨最高,其次为Ⅲ型和Ⅱ型降雨;土壤流失量为Ⅱ型降雨>Ⅰ型降雨>Ⅲ型降雨。最大30 min降雨强度与5种土地利用类型的径流系数和土壤流失量的正相关性最高,其次为降雨量、降雨历时。5种土地利用类型的平均径流系数为裸地>经济林地>坡耕地>草地>土坎梯田,土壤流失量为裸地>坡耕地>经济林地>草地>土坎梯田。降雨和土地利用相互作用下,径流和土壤流失因雨型和土地利用方式不同而存在差异性,且认为在控制土壤侵蚀和减少泥石流坡面物源方面应避免大规模种植油橄榄。[结论]最大30 min降雨强度是影响该流域降雨侵蚀力的关键降雨指标,土坎梯田可较好控制坡面侵蚀,草地的减流减沙效果显著,研究结果可为坡面水土流失和泥石流防治提供科学依据。

[Objective]The influence and effect of rainfall and land use on the slope erosion in the debris flow small watershed was revealed to provide scientific basis for ecological control of debris flow.[Methods]The first-level tributary of the Bailong River Basin—the debris flow small watershed of Ganjiagou was taken as the research area,and based on five consecutive years of observation data of the five runoff plots(bare land,sloping farmland,grassland,ridge terraces,economic forest land)that have been built in this watershed,K-means clustering method was used to divided the 46 erosive rainfall events in the basin into three rainfall regimes(type I,typeⅡ,typeⅢ)by selecting three rainfall indicators,such as rainfall(P),rainfall duration(D)and maximum 30 min rainfall intensity(I 30).The influence and effect of rainfall regimes and land use types on slope runoff and sediment production were quantitatively analyzed based on selecting the average runoff coefficient and average soil loss as the main indicators.[Results]There were differences in the response of runoff and soil loss to rainfall,the average runoff coefficient is the highest for type I rainfall,followed by typeⅢand typeⅡrainfall.The soil loss d ecreased in the order:typeⅡrainfall>type I rainfall>typeⅢrainfall.The maximum 30 min rainfall intensity had the highest positive correlation with the runoff coefficient and soil losses of the five land use types,followed by rainfall and rainfall duration.The average runoff coefficients of the five land use types decreased in the order:bare land>economic forest land>sloping farmland>grassland>ridge terraces,and the soil loss decreased in the order:bare land>sloping farmland>economic forest land>grassland>ridge terraces.Under the interaction of rainfall and land use,there were differences in runoff and soil loss due to different rainfall regimes and land use methods,and it was believed that large-scale planting of olive oil should be avoided in terms of controlling soil erosion and reducing the source of debris flow on slopes.[Conclusion]The maximum 30 min rainfall intensity is the key rainfall index affecting the rainfall erosivity in the basin,the slope erosion can be better controlled by the terraced soil,and the effect of reducing the runoff and sediment of the grassland is remarkable.This research results can provide a scientific basis for the prevention and control of soil erosion and debris flow on slopes.