中文摘要：

高含沙水流的频繁发生是黄土高原多沙粗沙区产生高强度侵蚀的重要原因。本文基于1967—1989年的系列泥沙资料和面雨量资料，分析了黄土高原多沙粗沙区8个流域高含沙水流发生频率随时间的变化过程。根据其不同的变化趋势，将研究区所有流域分成了两类。第一种类型高含沙水流发生频率随时间逐渐减小；第二种类型高含沙水流随时间呈先减小后增大的变化趋势。从汛期降雨量（6—9月）及人类活动（包括人为的减沙活动和人为增沙活动）两个方面对高含沙水流随时间变化趋势的产生原因进行了分析。结果表明，第一种类型主要受到同期汛期降雨量的减少以及各种水利水保措施减沙量从上世纪60一80年代逐渐增大的影响；第二种类型的流域在上世纪60年代末到80年代初高含沙水流发生频率的减小主要是因为上世纪60、70年代大量修建的淤地坝在70年代发挥了显著的拦减泥沙的作用；但到了80年代以后，新建淤地坝很少。原有淤地坝已大部失效，另外人为的增沙活动，如修路、开矿、建窑等活动在80年代以后显著增加，上述因素促使高含沙水流发生频率在80年代初期以后呈随时间增加的趋势。

英文摘要：

The hyperconcentrated flow is an important factor to the high intensity erosion of the high-intensity and coarse sediment producing area of the Loess Plateau. Based on the sediment and rainfall data in the period of 1967- 1989,the temporal variation in hyperconcentrated flow frequency in the 8 river basins in the high-intensity and coarse sediment producing area in the Loess Plateau was analyzed. All river basins were divided into two categories based on the similarity of the temporal variation trends of hyperconcentrated flow frequency ① hyperconcentrated flow frequencies decrease with time; ②hyperconcentrated flow frequencies decrease to minimum with time first and then increase. Two variation trends mentioned above were studied according to the precipitation in flood seasons （from June to September） and the human activities （the sedimentation reduced and increased by human activities）. For the first category the decreased precipitation in flood season and decadal increases of sediment reduced by soil and water conservation measures from 1960s to 1980s are the main factors for the hyperconcentrated flow frequency decrease with time. For the second category, checkdams built between 1960s and 1970s reduced large quantity of sediment from late 1960s to early 1980s, therefore the hyperconcentrated flow frequency decreased during this period. But since 1980, few new checkdams have been built, and most of the checkdams built before have been filled up and are no longer effective for reducing sediment, and thus the sediment supplied to each river basin has increased, so has the hyperconcentrated flow frequency. Meanwhile, the enhanced human activities such as road construction, coal mining, house building have increased erosion significantly and become other factors for the increase of hyperconcentrated flow frequency.