黄河流经西北黄土高原地区,由于汛期暴雨集中,大片植被较差地区水土流失严重,形成浓度极高的含沙水流,一场洪水中的含沙量可高达1,500公斤/立米以上。这种高含沙水流在中游山陕区间和径渭洛河地区(图1)虽然是屡见不鲜的,但近年来已有逐步向下游扩展的趋势。1977年7、8月间,黄河中下游相继出现两场高含沙洪水,其含沙量在龙门、华县以下直至花园口河段均接近或超过历史最高记录(表1)。两场洪水的沿程冲淤变化十分剧烈。第一场洪水沿程不少河段发生了“揭河底”现象,小浪底至花园口河段刷成深槽,平均刷深1.0～1.5米。第二场洪水在此河段发生了水位、流量的异常变化,出现了“浆河”现象。这样大的高浓度含沙水流进入下游河道以后发 The Yellow River flows through the northwestern Loess Plateau. Due to the heavy rainfall in the flood season and the serious soil erosion in areas with large vegetation, the sediment concentration in the floodwater can reach as high as 1,500 kg / m3. Although this high sediment-laden flow is commonplace in the mid-range Shanshan area and the Weiheiluohe area (Figure 1), it has been gradually expanding downstream in recent years. During July and August 1977, two high-level floods occurred successively in the middle and lower reaches of the Yellow River. The sediment concentrations in the middle and lower reaches of the Yellow River reached or exceeded the historical record below the Longmen and Huaxian rivers (Table 1). Scouring and silting changes along the two floods are very intense. The first flood along many river sections occurred “Jiehehe” phenomenon, Xiaolangdi to Huayuankou brush into deep grooves, the average depth of brush 1.0 to 1.5 meters. The second flood occurred in this section of the river, the abnormal flow changes, there has been “pulp river” phenomenon. Such a large high concentration of sandy water into the downstream after the river