scholarly journals Hydraulic characteristics and sediment generation on slope erosion in the Three Gorges Reservoir Area, China

2016 ◽  
Vol 64 (3) ◽  
pp. 237-245 ◽  
Author(s):  
Feng Qian ◽  
Dongbin Cheng ◽  
Wenfeng Ding ◽  
Jiesheng Huang ◽  
Jingjun Liu
Keyword(s):  
Soil Erosion ◽  
Sediment Yield ◽  
Rainfall Intensity ◽  
Purple Soil ◽  
Three Gorges ◽  
Slope Gradient ◽  
Stream Power ◽  
Yield Rate ◽  
The Three Gorges ◽  
Subsurface Runoff

Abstract Hydrological processes play important roles in soil erosion processes of the hillslopes. This study was conducted to investigate the hydrological processes and the associated erosional responses on the purple soil slope. Based on a comprehensive survey of the Wangjiaqiao watershed in the Three Gorges Reservoir, four typical slope gradients (5°, 10°, 15°and 20°) were applied to five rainfall intensities (0.6, 1.1, 1.61, 2.12 and 2.54 mm·min-1). The results showed that both surface and subsurface runoff varied greatly depending on the rainfall intensity and slope gradient. Surface runoff volume was 48.1 to 280.1 times of that for subsurface runoff. The critical slope gradient was about 10°. The sediment yield rate increased with increases in both rainfall intensity and slope gradient, while the effect of rainfall intensity on the sediment yield rate was greater than slope gradient. There was a good linear relationship between sediment yield rate and Reynolds numbers, flow velocity and stream power, while Froude numbers, Darcy-Weisbach and Manning friction coefficients were not good hydraulic indicators of the sediment yield rate of purple soil erosion. Among the three good indicators (Re, v and w), stream power was the best predictor of sediment yield rate (R2 = 0.884). Finally, based on the power regression relationship between sediment yield rate, runoff rate, slope gradient and rainfall intensity, an erosion model was proposed to predict the purple soil erosion (R2 = 0.897). The results can help us to understand the relationship between flow hydraulics and sediment generation of slope erosion and offer useful data for the building of erosion model in purple soil.

scholarly journals Hydraulic characteristics of varying slope gradients, rainfall intensities and litter cover on vegetated slopes

2017 ◽  
Vol 49 (2) ◽  
pp. 506-516 ◽  
Author(s):  
Jiamei Sun ◽  
Dengxing Fan ◽  
Xinxiao Yu ◽  
Hanzhi Li
Keyword(s):  
Reynolds Number ◽  
Sediment Yield ◽  
Rainfall Intensity ◽  
Forest Litter ◽  
Resistance Coefficient ◽  
Litter Layer ◽  
Slope Gradient ◽  
Power Functions ◽  
Yield Rate ◽  
Litter Cover

Abstract Litter produced by forests performs crucial functions in rainfall interception and soil conservation, particularly in the condition that larger raindrops formed by canopy accelerate soil erosion. To explore how forest litter exerts runoff hydrological characteristics and sediment yield processes, experiments on forest covered (Vitexnegundo var. heterophylla) slopes were conducted under various combinations of rainfall intensities and slope gradients. The results showed that litter reduced runoff yield rate by 9–31% and reduced sediment yield rate by 65–90%, with mean runoff and sediment reductions of 18% and 76% for all treatments. On forest covered slopes, Reynolds number and runoff power generally increased with the increase in both rainfall intensity and slope gradient. Litter layer reduced Reynolds number and runoff power with 8–29% and 56–80%, respectively. Darcy–Weisbach resistance coefficient decreased by increasing rainfall intensity and slope gradient. Litter layer increased Darcy–Weisbach resistance coefficient by three to nine times. Relationships between sediment yield rate and Reynolds number, runoff power, Darcy–Weisbach resistance coefficient were described by exponential, linear, power functions, respectively. The critical runoff power values for slopes with and without litter were 0.0027 and 0.0010 m/s, respectively. Reynolds number was the best hydrodynamic parameter for dynamic erosion characterizing.

scholarly journals Effects of Rainfall Intensity and Vegetation Cover on Erosion Characteristics of a Soil Containing Rock Fragments Slope

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Bingqin Zhao ◽  
Lun Zhang ◽  
Zhenyao Xia ◽  
Wennian Xu ◽  
Lu Xia ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Vegetation Cover ◽  
Three Gorges Reservoir ◽  
Rainfall Intensity ◽  
Sediment Load ◽  
Cynodon Dactylon ◽  
Three Gorges ◽  
Rock Fragments ◽  
Runoff Volume ◽  
The Three Gorges

Rainfall events coupled with shallow and gravelly sloping farmland have led to serious soil erosion and associated problems in the Three Gorges reservoir. Previous studies have shown that the use of vegetation is an effective way to control soil erosion. Therefore, an artificial, simulated rainfall experiment study is conducted to determine the effect of rainfall intensity and vegetation cover on runoff volume, sediment load, and runoff hydraulics characteristics. The experiment consists of seven vegetation treatments subjected to three rainfall intensities on a soil that contains rock fragments on a slope of 30°. The results indicate that the runoff volume and sediment load of the bare plot were greater than those of vegetation-covered plots under three different rainfall intensities. When Cynodon dactylon and Indigofera amblyantha were applied together, the plot displayed the best performance for soil loss control, with a reduction of 87.88%–99.11%. According to a redundancy analysis, the change in rainfall intensity had the least impact on the Reynolds number and the runoff volume of the herb-shrub mixed plot in this study. These findings suggest that the effect of combining Cynodon dactylon and Indigofera amblyantha and increasing the vegetation coverage is an effective solution for soil and water loss conservation. The application of this method can alleviate environmental stress on the Three Gorges reservoir.

Vertical variation of soil erosion resistance in the water-level fluctuation zone of the Three Gorges Reservoir, China

2020 ◽  
Author(s):  
Hai Xiao
Keyword(s):  
Soil Erosion ◽  
Three Gorges Reservoir ◽  
Erosion Resistance ◽  
Three Gorges ◽  
Stream Power ◽  
Vertical Variation ◽  
The Three Gorges ◽  
Unit Energy ◽  
Water Level Fluctuation Zone ◽  
Soil And Water

<p>The operation of the Three Gorges Reservoir (TGR) altered the distribution of the soil properties, the plant community composition and biomass in the water-level fluctuation zone (WLFZ). However, the vertical variation of soil erosion resistance in the WLFZ of the TGR is still unclear and need to be further evaluated. The objectives of this study were to assess the vertical variation of soil resistance to rill erosion in the WLFZ of the TGR and to identify the factors influencing these variations. Soil samples from 150-155 m, 155-160 m, 160-165 m, 165-170 m and 170-175 m were taken along a slope profile at the same time from the WLFZ of the TGR area. All the samples subjected to scour under the combinations of five slope gradients (8.74%, 17.63%, 26.79%, 36.40% and 46.63%) and five flow rates (5, 10, 15, 20 and 25 L min<sup>–1</sup>) by using a slope-adjustable steel hydraulic flume (4 m length, 0.4 m width, 0.2 m depth). The results showed that soil properties and biomass parameters were affected by the elevations of the WLFZ. The average soil detachment capacity fluctuated with the increase of elevation, maximum and minimum value of  which were located at the 165-170 m and 155-160 m, respectively. The soil detachment capacity was significantly negatively correlated with MWD (P<0.05), but not positively correlated with other properties (P>0.05).  The rill erodibility also fluctuated with the increase of elevation. Correlation analysis showed that rill erodibility corresponding to runoff shear stress and stream power respectively had significantly negative correlation with MWD (P<0.05), and rill erodibility corresponding to unit energy of water-carrying section had significant negative correlation with MWD (P<0.01). Therefore, the soil aggregate stability was the major factor responsible for the vertical variation in soil erosion resistance. In addition, critical shear stress, critical stream power and critical unit energy of water-carrying section ranged from 1.1950 to 1.6427 Pa, from 0.0132 to 0.3045 N•m<sup>-1</sup>•s<sup>-1</sup> and from 0.0052 to 0.0062 m, respectively, all of them showed obvious fluctuations with the increase of elevation. These research results highlighted the effect of elevation on soil erosion resistance in the WLFZ and provide theoretical guidance for the establishment of soil and water loss prediction model as well as the development of soil and water conservation planning and controlling in the TGR area.</p><p> </p>

Soil Erosion Process in Sloped Shrub Plots under Simulated Rainfall

2011 ◽  
Vol 347-353 ◽  
pp. 2094-2097 ◽  
Author(s):  
Pei Qing Xiao ◽  
Wen Yi Yao ◽  
Chang Gao Wang
Keyword(s):  
Soil Erosion ◽  
Sediment Yield ◽  
Rainfall Intensity ◽  
Infiltration Rate ◽  
Simulated Rainfall ◽  
Slope Gradient ◽  
Erosion Process ◽  
Infiltration Process ◽  
Negative Relation ◽  
Runoff And Sediment Yield

Runoff, sediment yield and infiltration process of shrub plots were studied under rainfall intensities of 45, 87 and 127 mm/h with 20° slope gradient using simulated rainfall experiment. The results showed that cumulative runoff and cumulative sediment yield of shrub plot had an obvious positive correlation with rainfall time. Under rainfall intensity of 45 mm/h, runoff and sediment yield of shrub plot kept a constant level. Under rainfall intensity of 87 mm/h, runoff kept a fluctuant increase, whereas sediment yield basically kept steady. Under rainfall intensity of 127 mm/h, runoff and sediment yield of shrub plot increased evidently due to the formation of erosion pits. Infiltration rate of shrub plot had a negative relation with runoff as well as sediment yield.

The effects of multiple factors on spring meltwater erosion on an alpine meadow slope

2021 ◽  
Author(s):  
Xiaonan Shi ◽  
Fan Zhang ◽  
Li Wang
Keyword(s):  
Soil Erosion ◽  
Sediment Yield ◽  
Alpine Meadow ◽  
Alluvial Soil ◽  
Strong Impact ◽  
The Tibetan Plateau ◽  
Slope Gradient ◽  
Multiple Factors ◽  
Total Runoff ◽  
The Impact

<p>Serious soil erosion is observed during the spring because soil thawing coincides with the period of snowmelt and low meadow coverage at this time. Studies relating to soil erosion caused by spring meltwater are limited and controversial. In this study, a field experimental study was conducted in an alpine meadow slope in the Binggou watershed on the northern edge of the Tibetan Plateau to assess the impact of multiple factors on spring meltwater erosion. The multiple factors included three flow rates, four slope gradients, and three underlying surface conditions (meadow, disturbed meadow, and alluvial soil). An equal volume of concentrated meltwater flow was used in all experiments. The results showed that rapid melting at a high flow rate could accelerate soil erosion. The influence of the slope gradient on the amount of runoff was positively linear and the influence was relatively low. However, the slope gradient had a strong impact on soil erosion. The meadow could effectively reduce soil erosion, although when the meadow was disturbed, the total runoff increased by 60% and the sediment yield by a factor of 1.5. The total runoff from the alluvial soil doubled in comparison to the meadow, while the sediment yield increased nearly 7-fold. The findings of this study could be helpful to understand the characteristics and impact of multiple controlling factors of spring meltwater erosion. It also aims to provide a scientific basis for an improved management of alpine meadows as well as water and soil conservation activities in high-altitude cold regions.</p><p> </p>

scholarly journals Mechanized and Optimized Configuration Pattern of Crop-Mulberry Systems for Controlling Agricultural Non-Point Source Pollution on Sloping Farmland in the Three Gorges Reservoir Area, China

2020 ◽  
Vol 17 (10) ◽  
pp. 3599
Author(s):  
Shouqin Zhong ◽  
Zhen Han ◽  
Jiangwen Li ◽  
Deti Xie ◽  
Qingyuan Yang ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Three Gorges Reservoir ◽  
Three Gorges Reservoir Area ◽  
Three Gorges ◽  
Point Source Pollution ◽  
The Three Gorges ◽  
Contour Hedgerow ◽  
Sloping Farmland ◽  
Contour Hedgerows ◽  
Non Point Source Pollution

High-intensity utilization of sloping farmland causes serious soil erosion and agricultural non-point source pollution (AGNSP) in the Three Gorges Reservoir Area (TGRA). Crop-mulberry systems are important agroforestry systems for controlling soil, water, and nutrient losses. However, there are many different mulberry hedgerow planting patterns in the TGRA. In this study, soil structure, nutrient buildup, and runoff nutrient loss were observed in field runoff plots with five configurations: P1 (two longitudinal mulberry hedgerows), P2 (two mulberry contour hedgerows), P3 (three mulberry contour hedgerows), P4 (mulberry hedgerow border), and P5 (mulberry hedgerow border and one mulberry contour hedgerow), as well as a control (CT; no mulberry hedgerows). P1 had the smallest percentage of aggregate destruction (18.8%) and largest mean weight diameter (4.48 mm). P5 led to the greatest accumulation of ammonium nitrogen (NH4+–N) and total phosphorus (TP) (13.4 kg ha−1 and 1444.5 kg ha−1 on average, respectively), while P4 led to the greatest accumulation of available phosphorus (AP), nitrate nitrogen (NO3−–N), and total nitrogen (TN) (114.0, 14.9, and 1694.1 kg ha−1, respectively). P5 was best at preventing soil erosion, with the smallest average annual runoff and sediment loss of 112.2 m3 ha−1 and 0.06 t ha−1, respectively, which were over 72.4% and 87.4% lower than those in CT, respectively. P5 and P4 intercepted the most N in runoff, with average NH4+–N, NO3−–N, particulate N, and TN losses of approximately 0.09, 0.07, 0.41, and 0.58 kg ha−1, respectively, which were 49.7%, 76.2%, 71.3%, and 69.9% lower than those in CT, respectively. P5 intercepted the most P in runoff, with average TP and total dissolved phosphorus (TDP) losses of 0.09 and 0.04 kg ha−1, respectively, which were 77.5% and 70.4% lower than those in CT, respectively. Therefore, the pattern with one mulberry hedgerow border and one mulberry contour hedgerow (P5) best controlled AGNSP, followed by that with only a mulberry hedgerow border (P4).

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