The proportion of jet flow and on-wall flow and its effects on soil loss and plunge pool morphology during gully headcut erosion

Guo, Mingming; Lou, Yibao; Chen, Zhuoxin; Feng, Lanqian; Zhang, Xingyi

doi:10.1016/j.jhydrol.2021.126220

Cited by 11 publications

(13 citation statements)

References 53 publications

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“…In terms of temporal variation, the Froude number of the runoff of the BL decreased linearly with time, while that of the grassland plot decreased exponentially. The variation trend in the Froude number over time was opposite to that of the Reynolds number, which is consistent with previous research results (Guo, Lou, et al, 2021; Zhang et al, 2016). Moreover, vegetation inhibited the increase in the Froude number.…”

Section: Discussionsupporting

confidence: 92%

“…For the BL, the tableland was exposed and the soil was highly erodible, which enabled the runoff to easily cut the soil down to form gullies (Figure 14d,e,f). Additionally, due to the presence of a gully head (Figure 13), the flow was divided into on‐wall flow and jet flow (Guo, Lou, et al, 2021). The flow velocity of the bare land was faster than that of the grassland plot.…”

Section: Discussionmentioning

confidence: 99%

“…When the concentrated flow reached the gully head, the runoff was divided into two parts. Part of the concentrated flow developed into on-wall flow, and the other part developed into jet flow (Guo, Lou, et al, 2021), which directly dropped to the gully bed. Compared with the velocity for the tableland, the jet flow velocity for the gully head increased by 2.97%-67.19%.…”

Section: Responses Of Runoff Characteristics To Grass Density In Gull...mentioning

confidence: 99%

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Effects of grass density on the runoff hydraulic characteristics and sediment yield in gully headcut erosion processes

Feng

Wang

Guo

et al. 2022

Hydrological Processes

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Vegetation plays a crucial role in gully headcut erosion. However, little is known about how grass influences runoff hydraulics, soil erosion and headcut erosion processes. A series of rainfall and scouring experiments were conducted on four plots to elucidate the effect of the density of Agropyron cristatum (L.) Gaertn (planting spaces: 20 × 20 cm2, GA1; 15 × 15 cm2, GA2; 10 × 10 cm2, GA3; bare land as control, BL) on runoff hydraulics and soil erosion during gully headcut erosion. The velocity, Reynolds number (Re), runoff shear force (τ) and stream power (ω) of the BL increased exponentially with time (P < 0.01). However, for the grassland, most parameters increased linearly with time (P < 0.01). The Froude number (Fr) of the BL and grassland significantly decreased linearly and exponentially, respectively, with time (P < 0.01). For τ, the grass tableland needed to develop for a period of time to restrain it. The runoff of the BL tableland and gully head was supercritical turbulent, while that of the grassland was more dispersed. The existence of a gully head increased the jet velocity by 2.97%–67.19%, which increased the dispersion degree of the runoff. The runoff energy showed a significant exponential increase with time (P < 0.05). Compared with that of the BL, the energy consumption of the runoff from the grassland increased by 4.10%–31.81%. During gully headcut erosion, the BL was primarily cut down to the tableland by runoff, while the grassland was cut down to the headwall by on‐wall flow. As the density increased, the benefit of sediment reduction increased, reaching a maximum of 66.79%. The collapse of the BL primarily occurred in the upper part of the headwall during the early experimental stage. The frequency and space–time ranges of the collapse of the grassland were larger than those of the BL. The gravity erosion types of the BL were headwall collapse and gully bank collapse, while those of the grasslands were headwall collapse and root‐soil composite collapse.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Responses Of Runoff Characteristics To Grass Density In Gull...mentioning

confidence: 99%

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Effects of grass density on the runoff hydraulic characteristics and sediment yield in gully headcut erosion processes

Feng

Wang

Guo

et al. 2022

Hydrological Processes

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“…These results of the study are consistent with those described by Govers (1992) and Ban et al (2017) for slope erosion, that is the flow rate is mainly influenced by the discharge flow. In addition, the presence of a GH leads to a reduction in the flow rate (Guo et al, 2021). This occurs in part because when run-off flows along a loess slope, most of the water is ejected into the GB as plunging water, thereby forming plunge pools (Zhang et al, 2018).…”

Section: Relationship Between the Headcut Height And Hydraulic Charac...mentioning

confidence: 99%

Dynamics of run‐off hydraulic characteristics during gully headcut erosion driven by head height

Tang,

Liao,

Lin

et al. 2023

Earth Surf Processes Landf

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In the granitic red soil hills region of South China, gully headcut erosion is considered one of the main processes in the development of gullies. However, the dynamics of run‐off hydraulic characteristics such as hydrodynamics and energy consumption during erosion have not been clarified. We investigated the effects of five headcut heights (25 to 125 cm) on hydrodynamic and energy consumption characteristics using field in situ water discharge scouring experiments. The results demonstrated that the flow velocity (V), Froude number (Fr), Reynolds number (Re), run‐off shear (τ) and run‐off power (ω) all indicate the upstream area (UA) > gully bed (GB). Except for V and Fr, several other hydraulic parameters exhibited a trend of sandy soil layer > red soil layer, and a fluctuating increase with increasing headcut height was observed in the GB. The jet velocity at the edge of the headcut (Vb), jet shear stress (τj), potential energy conversion (∆EP) and bottoming instantaneous kinetic energy (EKbottom) all increased exponentially with increasing headcut height by factors of 1.10 to 1.37, 1.16 to 2.00, 1.07 to 2.06 and 1.22 to 1.86, respectively. Except for ∆EP, all others performed a trend of sandy soil layer > red soil layer. The energy consumption at the gully head (∆EH) and its contribution tended to significantly increase with increasing headcut height, and the ∆EH of sandy soil layer was 13.20% to 49.89% higher than that of red soil layer. When the headcut height was greater than 100 cm, the contribution of energy consumption exceeded 50%. In addition, the sediment deposition process throughout the system was significantly influenced by the hydraulic and jet characteristics, and energy consumption was positively correlated with soil loss. The study results contribute to a profound understanding of gully headcut erosion and its hydrodynamic mechanisms.

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“…The current mean annual soil erosion rate has been reduced to 4350 Mg km −2 yr −1 in the study watershed (Guo et al, 2019). The plants are primarily artificially planted arbors and herbaceous vegetation and shrubs (Guo et al, 2021b).…”

Section: Study Areamentioning

confidence: 99%

Spatiotemporal changes in flow hydraulic characteristics and soil loss during gully headcut erosion under controlled conditions

Guo

Chen

Wang

et al. 2021

Hydrol. Earth Syst. Sci.

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Abstract. The spatiotemporal changes in flow hydraulics and energy consumption and their associated soil erosion remain unclear during gully headcut retreat. A simulated scouring experiment was conducted on five headcut plots consisting of upstream area (UA), gully headwall (GH), and gully bed (GB) to elucidate the spatiotemporal changes in flow hydraulic, energy consumption, and soil loss during headcut erosion. The flow velocity at the brink of a headcut increased as a power function of time, whereas the jet velocity entry to the plunge pool and jet shear stress either logarithmically or linearly decreased over time. The jet properties were significantly affected by upstream flow discharge. The Reynolds number, runoff shear stress, and stream power of UA and GB increased as logarithmic or power functions of time, but the Froude number decreased logarithmically over time. The Reynolds number, shear stress, and stream power decreased by 56.0 %, 63.8 %, and 55.9 %, respectively, but the Froude number increased by 7.9 % when flow dropped from UA to GB. The accumulated energy consumption of UA, GH, and GB positions linearly increased with time. In total, 91.12 %–99.90 % of total flow energy was consumed during headcut erosion, of which the gully head accounted for 77.7 % of total energy dissipation, followed by UA (18.3 %), and GB (4.0 %). The soil loss rate of the “UA-GH-GB” system initially rose and then gradually declined and levelled off. The soil loss of UA and GH decreased logarithmically over time, whereas the GB was mainly characterized by sediment deposition. The proportion of soil loss at UA and GH is 11.5 % and 88.5 %, respectively, of which the proportion of deposited sediment on GB reached 3.8 %. The change in soil loss of UA, GH, and GB was significantly affected by flow hydraulic and jet properties. The critical energy consumption initiating soil erosion of UA, GH, and GB is 1.62, 5.79, and 1.64 J s−1, respectively. These results are helpful for deepening the understanding of gully erosion process and hydrodynamic mechanisms and can also provide a scientific basis for the construction of gully erosion model and the design of gully erosion prevention measures.

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The proportion of jet flow and on-wall flow and its effects on soil loss and plunge pool morphology during gully headcut erosion

Cited by 11 publications

References 53 publications

Effects of grass density on the runoff hydraulic characteristics and sediment yield in gully headcut erosion processes

Effects of grass density on the runoff hydraulic characteristics and sediment yield in gully headcut erosion processes

Dynamics of run‐off hydraulic characteristics during gully headcut erosion driven by head height

Spatiotemporal changes in flow hydraulic characteristics and soil loss during gully headcut erosion under controlled conditions

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