Influence of Bottom Soil Layer Permeability and Slope Gradient on Runoff and Sediment Yield Characteristics

doi:10.11988/ckyyb.20231235

Abstract

Abstract:

Understanding the runoff and sediment yield processes on slopes are of crucial significance in enhancing the research on rainstorm and flood dynamics in mountainous areas. To examine the effects of slope soil permeability and gradient on runoff and sediment yield characteristics in mountainous terrain, an indoor artificial simulated continuous rainfall experiment was conducted. The experiment was conducted on a soil trough with shallow upper section and deep lower section using soil samples from the Guanshan River Basin. The study aimed to investigate and summarize the variations in runoff and soil erosion with different slope gradients. Findings reveal that 1) At 5° and 25° slopes, surface runoff rates increased with escalating rainfall intensity, with higher rates observed on slopes featuring impermeable bottom layers compared to those with permeable layers. At a 15° slope, however, runoff increased with notable fluctuations, and differences in runoff rates between impermeable and permeable bottom layers were not statistically significant. 2) Interflow rates escalated over time during each rainfall simulation, displaying significant variations across different slope gradients. Generally, interflow rates were higher on slopes with impermeable bottom layers than on those with permeable layers. Notably, the relationship between interflow rate and surface runoff rate was negatively correlated at 5° slopes and positively correlated at 25° slopes. 3) Surface runoff velocities increased with rising rainfall intensity. At 5° and 15° slopes, velocities were significantly higher on impermeable bottom layers compared to permeable ones, whereas at 25°, no significant differences were observed. 4) Soil erosion was most pronounced during the second and third rainfall simulations across different slope gradients. Erosion rates were higher on impermeable bottom layers compared to permeable ones at 5° and 25° slopes, but showed fluctuations at 15° slopes.

Key words: rainfall intensity, slope gradient, bedrock permeability, runoff and sediment yield, continuous rainfall

CLC Number:

S157.1

LIU Ji-gen, LU Liang-wei, TONG Xiao-xia, CHEN Jin-yang, GUO Yu-hui. Influence of Bottom Soil Layer Permeability and Slope Gradient on Runoff and Sediment Yield Characteristics[J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(2): 62-68.

Figures/Tables 9

Fig.1 Schematic diagram of indoor rainfall simulation apparatus

Fig.2 Surface runoff rate with impermeable and permeable bottom layers

Table 1 Statistics of total runoff yield

坡度/ (°)	设计雨强/ (mm·min^-1)	表面流总产流量/L		壤中流总产流量/L
坡度/ (°)	设计雨强/ (mm·min^-1)	透水	不透水	透水	不透水
5	0.5	4.95	18.43	2.40	3.69
	1.0	37.44	50.09	0.67	1.69
	1.5	60.70	81.11	0.51	1.77
	2.0	68.03	87.62	0.30	1.39
15	0.5	28.05	23.72	1.05	2.18
	1.0	47.86	43.25	0.37	3.75
	1.5	61.59	67.28	0.45	5.03
	2.0	79.44	75.64	0.34	4.81
25	0.5	2.32	2.70	0.08	0.00
	1.0	33.74	41.79	0.33	0.97
	1.5	52.55	64.55	0.34	0.31
	2.0	64.34	81.23	0.64	1.27

Fig.3 Interflow runoff rate with impermeable and permeable bottom layers

Fig.4 Surface flow velocity with impermeable and permeable bottom layers

Fig.5 Variation in surface erosion rate with impermeable and permeable bottom layers

Fig.6 Correlation between surface runoff rates and interflow runoff rates with impermeable and permeable bottom layers at different slope gradients

Fig.7 Correlation between surface runoff rate and erosion rate with impermeable and permeable bottom layers in each rainfall simulation

Table 2 Correlation between surface runoff rate and erosion rate

数据类别	透水性	回归方程	R²
全部数据	透水	D=0.115 35Q_b+0.050 79	0.256 12
全部数据	不透水	D=0.102 32Q_b+0.084 18	0.153 70
前3场数据	透水	D=0.221 42Q_b+0.002 44	0.663 13
前3场数据	不透水	D=0.251 9Q_b-0.004 54	0.682 54

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