Rill flow resistance law under equilibrium bed‐load transport conditions

Stefano, Costanza Di; Nicosia, Alessio; Pampalone, Vincenzo; Palmeri, Vincenzo; Ferro, Vito

doi:10.1002/hyp.13402

Cited by 23 publications

(18 citation statements)

References 45 publications

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“…At present, the contribution of sediment transport to rill flow resistance has been little investigated. The study by Di Stefano, Nicosia, Pampalone, Palmeri, and Ferro (2019) based on Jiang et al’s (2018) measurements established that flow resistance increases with bed load transport, in accordance with the available results for open channel flows (e.g., Gao & Abrahams, 2004). According to Di Stefano, Nicosia, Palmeri, Pampalone, and Ferro (2019), the impact of the overall (i.e., bed load and suspended) sediment transport on the flow resistance should be significantly lower than that of the grain roughness.…”

Section: Discussionsupporting

confidence: 65%

“…This result is due to a “feedback mechanism” because when slope gradient increases the expected increase of flow velocity is counterbalanced by the increase of bed roughness due to a more active rill erosion process. For the rills investigated by Jiang et al (2018) the feedback mechanism was not allowed because the flow could not shape the rill channel and was only able to transport the supplied sediment particles (Di Stefano, Nicosia, Pampalone et al, 2019). The result of a slope‐independent flow velocity obtained here can be attributed to the limited number of measurements characterized by a non‐erodible bed as compared to those carried out for a mobile bed condition.…”

Section: Discussionmentioning

confidence: 99%

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Flow resistance in mobile bed rills shaped in soils with different texture

Carollo

Stefano

Nicosia

et al. 2021

European J Soil Science

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Rill erosion is considered one of the most important soil processes because of the large amount of soil loss due to the development of a rill network able to promote an efficient transport of both rill flow‐detached particles and those delivered from the inter‐rill areas. Rill flow experiments are useful to overcome the gap in rill hydraulics knowledge and to test the reliability of currently applied uniform open channel flow equations for mobile bed rills. In this paper the applicability of a theoretical flow resistance equation, based on a power‐velocity profile, to rill channels shaped on soils having different textures was investigated. The measurements (437 runs) of water depth, cross‐section area, wetted perimeter, bed slope and flow velocity carried out in rill reaches shaped on experimental plots, having different slope values (9–26%) and soil texture (clay fraction range of 32.7–73%), were carried out. These measurements were jointly examined with 35 experimental runs carried out by other authors in a rill flume having a slope range of 18–84% and a clay content of 3%. The main aim of this paper is to deduce a relationship between the velocity profile parameter Γ, the channel slope and the flow Froude number using a database characterized by a wide range of slope (9–84%) and textural classes (clay ranging from 3 to 73%). The obtained relationship was also verified using 117 experimental runs carried out in this investigation by sloping plots (slope equal to 9 and 15%) with a soil having a clay content of 32.7%. The analysis demonstrated that the applicability of the theoretical flow resistance law is experimentally supported and that the effect of soil grain‐size distribution is represented by silt and clay fractions which take into account the influence of the detachability and transportability properties of the soil particles. Highlights Rill flow resistance is affected by interaction between flow, bed morphology and sediment transport. A new theoretical flow resistance law is tested for rills shaped on different textured soils. The velocity profile is related to the channel slope, the flow Froude number and the soil texture. The Darcy‐Weisbach friction factor can be accurately estimated by the proposed theoretical approach.

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Section: Discussionsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 99%

Flow resistance in mobile bed rills shaped in soils with different texture

Carollo

Stefano

Nicosia

et al. 2021

European J Soil Science

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“…At present, limited information on the effect of sediment transport on rill flow resistance is available. Di Stefano, Nicosia, Pampalone, et al (2019) using the measurements by Jiang et al (2018) established that flow resistance increases with bed load transport, in accordance with the available results for open channel flows (Gao & Abrahams, 2004). Furthermore, the impact of the overall (i.e., bed load and suspended) sediment transport on the rill flow resistance should be significantly lower than that of the grain roughness (Di Stefano, Nicosia, Palmeri, et al, 2019).…”

Section: Discussionsupporting

confidence: 71%

Estimating flow resistance in steep slope rills

Stefano

Nicosia

Palmeri

et al. 2021

Hydrological Processes

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Recent research recognized that the slope of 18% can be used to distinguish between the 'gentle slope' case and that of 'steep slope' for the detected differences in hydraulic variables (flow depth, velocity, Reynolds number, Froude number) and those representatives of sediment transport (flow transport capacity, actual sediment load). In this paper, using previous measurements carried out in mobile bed rills and flume experiments characterized by steep slopes (i.e., slope greater than or equal to 18%), a theoretical rill flow resistance equation to estimate the Darcy-Weisbach friction factor is tested. The main aim is to deduce a relationship between the velocity profile parameter Γ, the channel slope, the Reynolds number, the Froude number and the textural classes using a data base characterized by a wide range of hydraulic conditions, plot or flume slope (18%-84%) and textural classes (clay ranging from 3% to 71%). The obtained relationship is also tested using 47 experimental runs carried out in the present investigation with mobile bed rills incised in a 18%-sloping plot with a clay loam soil and literature data. The analysis demonstrated that: (1) the soil texture affects the estimate of the Γ parameter and the theoretical flow resistance law (Equation 25), (2) the proposed Equation (25) fits well the independent measurements of the testing data base, (3) the estimate of the Darcy-Weisbach friction factor is affected by the soil particle detachability and transportability and (4) the Darcy-Weisbach friction factor is linearly related to the rill slope.

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“…The proposed flow resistance equation was also tested using field data collected in 104 reaches of some Calabrian gravel bed rivers (Ferro and Porto 2018b). Di Stefano et al (2019a) tested the same theoretical flow resistance equation using 35 experimental runs of Jiang et al (2018) which investigated the effect of flow discharge and slope steepness on rill sediment transport capacity. The analysis confirmed that function can be estimated using the channel slope, the Shields number, and the Froude number and that the flow resistance law allows for an accurate estimate of the friction factor f.…”

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confidence: 99%

Rill flow resistance law under sediment transport

et al. 2021

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Purpose In this paper, a deduced flow resistance equation for open-channel flow was tested using measurements carried out in mobile bed rills with sediment-laden flows and fixed bed rills. The main aims were to (i) assess the effect of sediment transport on rill flow resistance, and (ii) test the slope-flow velocity relationship in fixed bed rills. Methods The following analysis was developed: (i) a relationship between the Γ function of the velocity profile, the rill slope and the Froude number was calibrated using measurements carried out on fixed bed rills; (ii) the component of Darcy-Weisbach friction factor due to sediment transport was deduced using the corresponding measurements carried out on mobile bed rills (grain resistance and sediment transport) and the values estimated by flow resistance equation (grain resistance) for fixed bed rills in the same slope and hydraulic conditions; (iii) the Γ function relationship was calibrated using measurements carried out on mobile bed rills and the data of Jiang et al. (2018). Results This analysis demonstrated that the effect of sediment transport on rill flow resistance law is appreciable only for 7.7% of the examined cases and that the theoretical approach allows for an accurate estimate of the Darcy-Weisbach friction factor. Furthermore, for both fixed and mobile beds, the mean flow velocity was independent of channel slope, as suggested by Govers (1992) for mobile bed rills. Conclusions The investigation highlighted that the effect of sediment transport on rill flow resistance is almost negligible for most of the cases and that the experimental procedure for fixing rills caused the unexpected slope independence of flow velocity.

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Rill flow resistance law under equilibrium bed‐load transport conditions

Cited by 23 publications

References 45 publications

Flow resistance in mobile bed rills shaped in soils with different texture

Flow resistance in mobile bed rills shaped in soils with different texture

Estimating flow resistance in steep slope rills

Rill flow resistance law under sediment transport

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