黄土丘陵沟壑区梯田暴雨侵蚀状况及规律分析

针对2013年延安百年不遇暴雨造成的黄土丘陵沟壑区梯田侵蚀灾害严重、水土资源利用率低等问题。选取安塞县马家沟流域曹新庄梯田作为典型研究对象，在进行野外监测的基础上，分析了梯田在百年不遇暴雨条件下的梯级侵蚀灾害发生规律。结果表明:按高程最上级梯田侵蚀轻微，依次往下梯田侵蚀面积所占百分比逐渐增大并且增加明显，上部梯田主要以面蚀为主，仅发生轻微沟蚀，下部梯田面蚀、沟蚀都比较严重。梯田侵蚀量与梯田汇水面积、地表径流量等条件有关，影响梯田侵蚀灾害发生的主要因素是地表径流量。该区2013年6—9月延安百年不遇暴雨梯田平均侵蚀模数为20 659.7 t/hm²，超过该区平均年侵蚀模数的47.6%，6—9月月降雨量侵蚀的临界值为118.8 mm。布置水沙调控措施层层拦蓄径流是保证梯田安全的重要措施。

Analysis of Rainstorm Erosion Disaster in Terrace Field in Loess Hilly and Gully Region

In view of the occurrence of serious terrace rainstorm erosion disaster and low utilization of soil and water resources problems in Yan'an in 2013, this article selects the Caoxinzhuang terraced field in Majiagou watershed as a typical terrace research site. On the basis of field monitoring, we analyzed the terraces in the worst storm regularity of cascade erosion disaster conditions. The results showed that: according to the elevation, the highest terrace erosion was slight, the percentage of erosion area increased gradually and significantly as terrace area increased. The higher terraces are mainly composed of sheet erosion with only slight gully erosion. In the lower terrace sheet erosion and gully erosion were serious. Terraced field erosion related to such conditions as the terrace catchment area, surface runoff, the main factor influencing the terraces erosion disaster is the sheet runoff. The average erosion modulus of terraced field is 20 659.7 t/hm² in Yan'an from June to September which is 47.6% more than average annual erosion modulus in this region. The critical value of rainfall causing erosion is 118.8 mm each month from June to September. The arrangement of water and sediment regulation measures is an important measure to guarantee the security of a terrace.