喀斯特黄壤区侵蚀性降雨及产沙特征分析

侵蚀性降雨研究是坡面侵蚀计算的前提性工作，以往喀斯特黄壤区的有关研究多因数据序列较短难以得出有效结论，或更集中于微观过程的观测，不能推广到自然状况下大尺度上的研究应用。确立降雨侵蚀力指标结构及不同下垫面的侵蚀性降雨标准，并结合相关背景资料模拟流域降雨侵蚀状况，对于喀斯特黄壤区的水蚀预报具有重要价值。文章分别观测了贵州中部和西部2个小流域的耕地、草地和人工林地3种径流小区5年的降雨产沙数据。通过计算最小降雨侵蚀力偏差系数Rcv对应的雨量雨强标准，并应用错选度，剔除率和损失率3个指标进行对雨量和雨强标准进行评定，在此基础上分析该区域的侵蚀性降雨分布和不同下垫面的产沙特征，得出以下结论：1）降雨动能和最大30 min降雨强度乘积为计算降雨侵蚀力指标的最佳结构形式，降雨侵蚀力指标可以通过降雨量和最大30 min降雨强度乘积进行简易计算；2）黄壤裸地的侵蚀性降雨指标应采用最大30 min降雨强度，其值在9.6-10.2 mm＆#183;h-1之间，耕地的侵蚀性降雨指标应采用雨量标准，其值在15 mm左右，水土保持措施可明显提高侵蚀性降雨标准，较裸地和耕地分别提高55%和25%以上，复杂下垫面宜采用雨量标准，低植被覆盖下垫面宜采用最大时段雨强标准；3）贵州西部和中部侵蚀性降雨总量分别占年降雨总量的36%和38%，主要分布在5-8月，研究区年均降雨侵蚀力在1700-1800（MJ＆#183;mm＆#183;hm-2＆#183;h-1＆#183;a-1），明显低于同纬度带的红壤和紫色土；坡面产沙量年内分布极为不均，少数的暴雨贡献了绝大部分的产沙量；4）无人为干扰的灌木草地水土保持效果最佳，顺坡耕作玉米严重加剧土壤侵蚀，减少人为扰动是治理的关键。

Erosive Rainfall and Characteristics Analysis of Sediment Yield on Yellow Soil Area in Karst Mountainous

Erosive rainfall research is the basis of calculation of slope erosion. Because of the short data sequence, it is difficult to draw valid conclusions in previous research on yellow soil area in karst mountainous. Some studies focus on the micro process of observation that can＆#39;t spread on the large scale application for natural conditions. To establish the erosive rainfall index and its standard for different underlying surface and simulate the condition of watershed rainfall-erosion with relevant background information have important significance to the water erosion prediction of yellow soil area in karst mountainous. Two small watershed are observed separately in the central and western of Guizhou from 2009 to 2013. The data of rainfall and sediment yield for plough, grassland and man-made forest runoff plot are recorded in each watershed. Then the minimum deviation factor of rainfall erosivity and their corresponding precipitation and rainfall intensity standard can be calculated by the runoff plots data. Relative error, elimination rate and loss rate have been used to evaluate the optimal erosive rainfall standard. On the basis of these results, relevant indexes about erosive rainfall and characteristics of sediment yield in different underlying surface were researched. The conclusions of the study can be drawn as follows：1） The best structure of rainfall erosive agent index is the product of rainfall kinetic energy and maximum 30 min rainfall intensity. Rainfall erosive agent index can be also calculated with the product of rainfall amount and maximum 30 min rainfall intensity. 2） The erosive rainfall index of bare yellow soil should use maximum 30min rainfall intensity with the value range from 9.6 to 10.2 mm＆#183;h-1, and the plough use rainfall amount standard better which is about 15mm. Soil and water conservation measures can increase erosive rainfall standard apparently. 3） Erosive rainfall account for 36%and 38%of the total rainfall in the central and western of Guizhou for the average