黄土高原丘陵沟壑区坡面-沟道系统中的高含沙水流(Ⅰ)——地貌因素与重力侵蚀的影响

Sediment-heavily containing flows in slope-channel systems of gullied hilly area in the Loess Plateau(Ⅰ):Influences of landforms and gravitational erosion

以黄河中游多沙粗沙区子洲径流站和离石王家沟试验站的径流场观测资料为基础,对黄土高原丘陵沟壑区坡沟系统中高含沙水流特征与地貌因素及重力侵蚀的关系进行了研究。研究结果表明,黄土坡面的地貌垂直结构和由此所决定的侵蚀作用垂直分异,对坡面高含沙水流的形成有很大的影响,高含沙水流形成于峁坡下部和沟坡,并在各级沟道中进一步发展。坡度对高含沙水流的形成有较大影响,如果侵蚀过程以溅蚀、面蚀、细沟侵蚀为主,不发生切沟及显著的重力侵蚀,则存在着一个坡度临界值,大于此值后,含沙量反而减小。重力侵蚀对坡沟系统高含沙水流的形成起着十分重要的作用,由于强烈的重力侵蚀的参与,高含沙水流的沙峰滞后于洪峰,落水阶段的含沙量常常大于同流量下涨水阶段的含沙量。

Based on the data from Zizhou and Wangjiagou Experimental Stations in the coarse sediment-producing area of the middle Yellow River drainage basin, this study deals with relationship of sediment-heavily containing flows in slope-channel systems of the gullied hilly areas with the landforms and gravitational erosion. The results show that the formation of sediment-heavily containing flows can be closely related to the vertical differentiation of landforms. The sediment-heavily containing flows is found to be formed in the lower part of Mao slopes and gully slopes, and they are further developed in the channel of gullies in various orders. Slope steepness is an important factor controlling the formation of sediment-heavily containing flows. If the sloping process is predominated by splash, sheet and rill erosions, and no channel erosion and mass movement occur, then a critical value of slope steepness would be observed, and the suspended sediment concentration is decreas for the lower or higher slope,. Gravitational erosion plays an important role in the formation of sediment-heavily containing flows. Due to the participation of strong gravitation erosion, the peaks of suspended sediment concentration usually lag behind the flood peaks, and the sediment concentration during the rising stage of a flood is usually smaller than that during the descending stage.