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Flow resistance in mobile bed rills shaped in soils with different texture
Author(s) -
Carollo Francesco G.,
Di Stefano Costanza,
Nicosia Alessio,
Palmeri Vincenzo,
Pampalone Vincenzo,
Ferro Vito
Publication year - 2021
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/ejss.13093
Subject(s) - rill , froude number , flume , geology , flow (mathematics) , soil water , geotechnical engineering , soil science , hydraulics , open channel flow , channel (broadcasting) , range (aeronautics) , flow velocity , hydrology (agriculture) , geometry , mathematics , materials science , engineering , composite material , electrical engineering , aerospace engineering
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.