Analysis of Runoff and Sediment Losses from a Sloped Roadbed under Variable Rainfall Intensities and Vegetation Conditions

Exploring Applicability of Different Ecological Protection Measures for Soil and Water Loss Control of Highway Slope in the Permafrost Area: A Case Study of Qinghai-Tibet Highway in China

A variety of slope water and soil conservation measures have been taken along the Qinghai-Tibet Highway, but the systematic comparison of their erosion control ability needs to be strengthened, especially in the permafrost area. To explore the applicability of different measures to control runoff and sediment yield, field scouring experiments were conducted for different ecologically protected slopes, including turfing (strip, block, full), slope covering (gravel, coconut fiber blanket), and comprehensive measures (three-dimensional net seeding). Compared with the bare slope, the bulk density of the plots with the ecological protection measure decreased, the moisture-holding capacity and the organic matter increased correspondingly, and the average runoff velocity also decreased. The soil loss and runoff had a similar trend of different ecological protection measures. The relationship between the cumulative runoff and sediment yield of different measures exhibited a power function, with the increase of scouring flow and the runoff reduction benefit and sediment reduction benefit in different ecological protection-measured plots showing a decreasing trend. The average runoff reduction benefit decreased from 37.06% to 6.34%, and the average sediment reduction benefit decreased from 43.04% to 10.86%. The comprehensive protection measures had the greatest protection efficiency, followed by turfing, while the cover measure had limited improvement. Soil characteristics, vegetation coverage, and the scouring inflow rate are key factors that influence protection efficiency. The results suggest that comprehensive measures and turfing be taken rather than cover measures or bare slopes. This work provides an experimental reference for ecological protection methods for highway slopes in the permafrost area.

Soil Remediation of Subtropical Garden Grasses and Shrubs Using High-Performance Ester Materials

Soil erosion due to rainstorms is a serious problem in subtropical gardens in South China. Soil conservation and the restoration of degraded landscapes are important research topics at home and abroad. Because of the sluggish growth of plants under traditional cultivation techniques, they are incapable of effectively protecting the soil. Therefore, the rapid and high-quality soil conservation of subtropical landscapes remains an urgent problem to be overcome. The purpose of this study is to improve the red soil and ground environment for the growth of grasses and shrubs through high-performance ester materials. Our objective was to find a solution for the high impact of soil loss on subtropical landscapes. In this study, we used the ecological restoration of soil as the starting point and selected a typical subtropical garden in South China as the field test point. We carried out soil erosion resistance testing using high-performance ester materials. The anti-erosion abilities of slopes under various working conditions are discussed. During the growth period, the soil indexes were monitored for a long time, and the growth of grasses and shrubs was compared. The obtained monitoring data were analyzed with mathematical statistics. We found that the addition of high-performance ester materials significantly reduced soil loss by 52.60%. High-performance ester materials have a good hydrothermal regulation function, which can promote the germination and later growth of sloping plants. The decrease in ground internal density promotes the extension of plant roots. High-performance ester materials can improve soil permeability and activity and promote vegetation growth. In terms of turf thickness and overall growth as well as shrubs crown width and height, high-performance ester materials have a beneficial effect on promoting plant growth. Soil remediation using high-performance ester materials has good economic value, high water-holding capacity, adaptability, and convenience. In this study, we determined a solution for the high impact of soil loss on subtropical landscapes. The soil remediation of a subtropical garden using high-performance ester materials was successful. The practice of landscape soil remediation engineering presented in this paper can provide a reference for typical landscape soil remediation in subtropical zones.

Erosion Control and Growth Promotion of W-OH Material on Red Clay Highway Slopes: A Case Study in South China

Ecological restoration is difficult on the red clay highway slopes in the rainy areas in South China that experience severe soil erosion. By using the hydrophilic polyurethane material W-OH to solidify and protect red clay slopes, the erosion control will be substantially improved. We employed simulated rainfall erosion experiments and pot experiments to evaluate the anti-corrosion and growth promotion performances. We found that, (1) in the initial stage of protection, W-OH had the effect of accelerating slope drainage, solidifying the soil structure, and reducing soil loss, with the sediment reduction benefit reaching 37.4–65.3%. (2) The anti-erosion effect was mainly based on soil solidification. (3) The W-OH was affected by rainfall intensity and the W-OH concentration, and the soil erosion prediction equation was constructed according to the observation. (4) W-OH had a promising water retention performance and can promote the germination and late growth of slope plants to reduce the influence of eluviation. (5) The suitable W-OH solution concentration was 3–5% for slope protection herbs and shrubs, which were commonly used in South China. (6) The reduction in porosity was the fundamental cause of water retention improvement. The ecological restoration of slopes is a comprehensive process. Therefore, both anti-erosion performance and later plant growth are necessary. Our research provides a theoretical and experimental basis for applying the W-OH in the ecological restoration of the red clay slopes in subtropical areas and expanding the scope of the W-OH.