侵蚀性降雨分类及植被类型对产流产沙的影响

Effects of Erosive Rainfall Classification and Vegetation Types on Runoff and Sediment Load Generation

为探索各类侵蚀性降雨及不同植被类型对产流产沙的影响,利用K-均值聚类分析法对黄土丘陵沟壑区安家沟流域布设的乔木林、灌木林、人工草地、天然草地和农作物等5种径流小区2014-2018年降雨、径流、泥沙观测资料进行了分析。结果表明:研究区侵蚀性降雨发生在5-9月,其中8月的侵蚀性降雨量及其产生的径流模数、侵蚀模数最大;可把侵蚀性降雨分为中雨量小雨强、中雨量大雨强、大雨量中雨强、大雨量超大雨强、暴雨量超大雨强等5种类型,出现的频率分别为42.85%、34.29%、14.29%、5.71%、2.86%;径流模数与侵蚀性降雨量、最大30 min雨强呈极显著相关,与降雨时长、平均雨强呈显著相关;产沙模数与侵蚀性降雨量、最大30 min雨强、平均雨强、降雨时长呈极显著相关,降雨量大且强度高的降雨是产生强烈侵蚀的主要动力来源;不同植被类型对产流产沙的调节作用差异较大,在大雨量情况下地表覆盖程度对产流产沙影响较大,地表覆盖度较高、对地表扰动小的林地和天然草地产沙模数较小,人工草地和农地因施肥、除草、收割等对地表扰动大且导致地表裸露时间长而产沙模数较大。

In order to explore the effect of various erosive rainfall and vegetation type on runoff and sediment yield,K-means clustering analysis method was used to analyze the observation data of rainfall,runoff and sediment of the five runoff plots of arbor forest,bush forest,artificial grassland,natural grassland and crops laid out in Anjiagou small watershed in the gullied rolling loess area in the period from 2014 to 2018.The results show that the erosive rainfall in the study area occurs from May to September,among which,the August erosive rainfall and its runoff modulus and erosion modulus are the largest.The erosion rainfall can be divided into 5 types of moderate rainfall light rainfall intensity,moderate rainfall and heavy rainfall intensity,heavy rainfall and medium rainfall intensity,heavy rainfall and excess heavy rainfall intensity,rainstorm amount and excess heavy rainfall intensity.The occurrence frequency is 42.85%,34.29%,14.29%,5.71%and 2.86%respectively.Runoff modulus is extremely significantly correlated with erosive rainfall and the maximum 30-min rainfall intensity is correlated significantly with rainfall duration and average rainfall intensity.Sediment yield modulus is significantly correlated with erosive rainfall,the maximum 30-min rainfall intensity,average rainfall intensity and rainfall duration.Heavy and intense rainfall is the main source of power for strong erosion.Different vegetation types have different regulating effects on runoff and sediment yield.Under heavy rainfall conditions,the degree of surface coverage has a greater impact on runoff and sediment yields.Forest land and natural grassland with higher surface coverage and less disturbance to the surface has lower modulus of sediment production.Artificial grassland and farmland have a high sediment yield modulus due to the large disturbance and long exposure time of the ground surface because of fertilization,weeding and harvesting.