Abstract
Grass strips can decrease erosion, trap sediment in silt-laden water flowing downhill, and control nonpoint source pollution. Determining the effects of different parts of grass strips on silt-laden overland flow will improve our understanding of sediment trapping by grass strips with different structures. Sediment trapping by grass strips was studied using a 5° slope, 30 L min−1 m−1 flow rate, 120 g L−1 sediment concentration, and different aboveground components of grass strips (complete grass, removed green grass, and removed green and withered grass). The whole overland flow process was monitored. Meanwhile, the runoff sediment samples at the outlet were collected and measured. Sediment trapping by aboveground grass parts was quantified at different stages. Of the soil bed surface, green grass, and withered grass, the soil bed surface dominated sediment trapping in the initial stage of the sediment-trapping process, contributing about 90% of total sediment deposition in the first 5 min. As the sediment-trapping process continued, the effect of the soil bed surface weakened, and the green grass played a major role at the later stage of sediment trapping. The ratio of the soil bed surface, green grass, and withered grass contributions to total sediment deposition at the stable stage of the experiments was approximately 3:5:2. The results will help assess the effects of vegetation restoration on sediment transport in entire watersheds.
Highlights
Published: 7 July 2021The main way desertification/land degradation can be prevented or reversed is by increasing or at least maintaining vegetation cover [1]
Compared with Mu et al under the conditions of artificial stem mulching with nine gradients in the range of 0–30% in the same trough [17], the results show that the effect of stem on the kinetic energy of the overland flow is stronger than that of litter
No clear gentle increase stage occurred at the beginning of the Remove green grass (RG) group experiments or Remove green and withered grass (RGW) group experiments (Figure 2)
Summary
The main way desertification/land degradation can be prevented or reversed is by increasing or at least maintaining vegetation cover [1]. A grass strip can improve the roughness of a hillslope surface and increase resistance to silt-laden overland flow [2,3]. Litter, the soil surface microtopography, small gravel particles (~0.5 mm diameter), and small stones all play important roles in the processes through which grass strips trap sediment [4,5]. The sediment-trapping efficiency is the percentage of the total amount of sediment flowing into a grass strip that is trapped [6]. The sediment-trapping efficiency is determined by overland flow rate, sediment concentration, particle size, topography, and vegetation characteristics [7]. The sediment-trapping effect of a grass strip is often described using an overall sediment-trapping efficiency for a certain period [8], but this does not indicate temporal variations in sediment trapping by the grass strip [9]
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