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2 results on '"Cheng, Shengdong"'

1. Establishment of a sediment transport capacity equation on loessal slope via experimental investigation.

Author

Wang, Tian, Li, Jingsi, Hou, Jingming, Li, Peng, Cheng, Shengdong, Wang, Feng, Wang, Wen, Li, Zhanbin, and Hinkelmann, Reinhard

Abstract

A reliable sediment transport capacity function provides response against challenges of soil erosion prediction on the Loess Plateau of China. The popular sediment transport capacity functions are questionable on loess slopes because the experimental conditions from which they were derived, like bed materials, gentle slopes, and surface roughness, are different from soil erosion processes on the loess slopes. Due to the foregoing uncertainty, a suitable sediment transport capacity function was developed based on a flume experiment investigation. The erodible bed experiment was implemented for five unit width discharges (1.3 × 10−4–3.3 × 10−4 m2/s) and ten slopes (5.2%–57.7%). The selected sediment transport capacity equations were tested in an applicability evaluation. The results of this evaluation found that the Govers (1990) function had the best performance (P.O. 0.5-2.0 = 76%, R 2 = 0.93, RMSE = 0.03 kg/(m·s)), followed by the Yalin (1963) function (P.O. 0.5-2.0 = 80%, R 2 = 0.81, RMSE = 0.05 kg/(m·s)), and finally by the Low (1989) function (P.O. 0.5-2.0 = 72%, R 2 = 0.79, RMSE = 0.04 kg/(m·s)), where P.O. 0.5-2.0 is the percentage of estimated values with logarithmic discrepancies with the measured value between 0.5 and 2.0; R 2 is the coefficient of determination and RMSE is the roof mean squares error. The cohesive sediment incipient motion velocity is introduced into the Govers (1990) function, and the sediment particle parameter is determined from measured experimental data. The developed sediment transport capacity equation has good performance with predicted values corresponding to measured values (P.O. 0.5-2.0 = 98%, R 2 = 0.98, RMSE = 0.006 kg/(m·s)). The research results provide an improved sediment transport capacity function on the basis of experiments for steep loessal slopes. • The cohesion sediment incipient motion velocity is introduced into the Govers (1990) function. • The sediment transport capacity was established for steep loessal slopes. • The developed sediment transport capacity has a good performance for prediction. [ABSTRACT FROM AUTHOR]

Published
2023
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2. Soil hydraulic conductivity as affected by vegetation restoration age on the Loess Plateau, China

Author

Ren, Zongping, Zhu, Liangjun, Wang, Bing, and Cheng, Shengdong

Abstract

The Loess Plateau of China has experienced extensive vegetation restoration in the past several decades, which leads to great changes in soil properties such as soil bulk, porosity, and organic matter with the vegetation restoration age. And these soil properties have great effect on the soil infiltration and soil hydraulic conductivity. However, the potential changes in soil hydraulic conductivity caused by vegetation restoration age have not been well understood. This study was conducted to investigate the changes in soil hydraulic conductivity under five grasslands with different vegetation restoration ages (3, 10, 18, 28 and 37 years) compared to a slope farmland, and further to identify the factors responsible for these changes on the Loess Plateau of China. At each site, accumulative infiltration amount and soil hydraulic conductivity were determined using a disc permeameter with a water supply pressure of –20 mm. Soil properties were measured for analyzing their potential factors influencing soil hydraulic conductivity. The results showed that the soil bulk had no significant changes over the initial 20 years of restoration (P>0.05); the total porosity, capillary porosity and field capacity decreased significantly in the grass land with 28 and 37 restoration ages compared to the slope farmland; accumulative infiltration amount and soil hydraulic conductivity were significantly enhanced after 18 years of vegetation restoration. However, accumulative infiltration amount and soil hydraulic conductivity fluctuated over the initial 10 years of restoration. The increase in soil hydraulic conductivity with vegetation restoration was closely related to the changes in soil texture and structure. Soil sand and clay contents were the most influential factors on soil hydraulic conductivity, followed by bulk density, soil porosity, root density and crust thickness. The Pearson correlation coefficients indicated that the soil hydraulic conductivity was affected by multiply factors. These results are helpful to understand the changes in hydrological and erosion processes response to vegetation succession on the Loess Plateau.

Published
2016
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