水保所知识产出(1956---)知识库

沟头溯源侵蚀占坡面细沟侵蚀量的 60%以上。该文运用立体摄影测量技术和人工模拟径流冲刷的方法，研究不
同流量和坡度下沟头溯源侵蚀过程及其产沙特征，探讨沟头下切造成的地表形态变化对坡面产沙的影响。结果表明：1）
坡面产沙率和沟头溯源侵蚀速率随流量和坡度的增加而增大。流量每增加 1 L/min，产沙率增加 0.59～5.34 倍；坡度从 15°
增加到 20°，产沙率增加 14.0%～89.7%。2）当流量小于或等于 2 L/min 时，产沙率在试验初期增加较快，而后缓慢上升；
当流量大于2 L/min时，产沙率始终保持快速上升趋势，沟头溯源长度达到100 cm所需时间较流量为1 L/min时缩短12 min
以上。3）坡度对沟头溯源侵蚀速率的影响随流量的增加逐渐减弱。4）细沟长度随时间的变化受流量和坡度的影响，其
值可由线性增函数表达；产沙率受沟头溯源侵蚀速率、沟头跌坎高度和沟头下方沟槽内发育的二级沟头数影响，其值可
由多元非线性回归方程表示。研究结果可为沟头溯源侵蚀预报模型建立和坡面水土保持措施布设提供理论依据。

 Headcut erosion constitutes more than 60% of hillslope soil loss. Quantitative research on rill headcut erosion
processes provides fundamental information for process-based erosion modeling. Due to the complicated headcut
morphologies and flow regimes near a headcut, it is hard to accurately predict the erosion rate of a headcut in some soil erosion
prediction models. Current knowledge on the impacts of headcut height, headcut advancing rate and secondary headcuts
developed on well-formed rill channel on soil loss is limited. Thus, simulation experiments with pre-made initial headcuts
(5 cm high) were designed to investigate the effects of inflow rate, slope gradient, headcut height and headcut number on rill
head advancing process. Soil boxes (2.0 m long, 0.3 m wide and 0.5 m deep) with 2 slope gradients (15° and 20°) and 4 inflow
rates (1.0, 2.0, 3.0 and 4.0 L/min) were subjected to upland concentrated flow. At slope lengths of 70 and 120 cm, 2 cameras
were mounted 1.5 m over the soil box and were controlled by an infrared remote control to photograph simultaneously. High
precision DEMs (digital elevation models) obtained by photogrammetry were used to detect changes of hillslope morphology
and headcut advancing process. The results showed that sediment delivery and headcut advancing rate increased while initial
headcut height and secondary headcut number did not strictly increase with the increase of inflow rate and slope gradient.
Sediment delivery increased by 0.59-5.34 times and 14.0%-89.7% when inflow rate increased by 1 L/min and slope gradient
increased from 15° to 20°, respectively. When inflow rate was equal to or smaller than 2 L/min, sediment delivery increased
fast at the beginning and kept stable later. When inflow rate was greater than 2 L/min, sediment delivery kept increasing during
the whole experiment. So, 2 L/min was a threshold of inflow rate that may cause rill head advancing rate to increase
significantly. Compared to the treatments at 1 L/min inflow rate, the duration for a headcut retreating by a certain length
(100 cm) was shortened by more than 12 min when inflow rate was greater than 2 L/min. The effects of slope gradient on rill
head advancing decreased with the increase of inflow rate. Linear equation which included unit flow rate and slope gradient
was used to predict the rill length time series. Relative errors between predicted values and observed values were smaller than
16% and both the R 2 and the Nash coefficient values were greater than 0.95. Soil loss on the hillslope dominated by rill head
advance was determined by headcut advancing rate, headcut height and the number of secondary headcuts developed below
the initial headcut. Soil loss increased with the increase of headcut advancing rate or headcut height in a power function while
showed a linear correlation with the number of secondary headcuts. Soil loss can be modeled with a non-linear regression
equation with a determination coefficient of 0.932. Results of this study provide new knowledge on rill headcut modeling. It is
recommended that upslope runoff should be intercepted and concentrated rill flow velocity should be reduced when soil and
water conservation practices are designed on steep loessial hillslope.