Sediment retention by a stiff grass hedge under subcritical flow conditions

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Title Sediment retention by a stiff grass hedge under subcritical flow conditions
Author Hussein, Janet; Ghadiri, Hossein; Yu, Bofu; Rose, Calvin Wyatt
Journal Name Soil Science Society of America Journal
Year Published 2007
Place of publication United States
Publisher Soil Science Society of America
Abstract Reduction of diffuse fluxes of sediments from catchments is frequently achieved through use of vegetative buffers, but the dynamics of this reduction are not fully understood. The physical processes involved in sediment deposition by a stiff grass buffer (hedge) at a low, subcritical, flow rate were therefore examined. Flow experiments were carried out in the Griffith University Tilting-Flume Simulated Rainfall facility using a 0.3 m width, vetiver hedge (Vetiveria zizaniodes L., sterile cultivar Monto) at 5% slope. Sediments comprising a sandy soil (Podzol) and red clay (Ferralsol) were introduced into the flow upstream of the buffer and the resultant hydrology, sediment deposition and outflow characteristics were measured. Flow retardation produced a backwater upstream of the vetiver hedge and sediment deposition varied with soil type in this backwater. The backwater region was greatly extended by the deposition process, increasing overall sediment trapping efficiency. Buffering action reduced mean sediment loads in the outflow to 3.2% and 6.0% of the inflow concentration for the Podzol and Ferralsol, respectively, with a significant difference (P<0.01) between the soils. In contrast to other buffer research where deposited sediments were coarsest upstream of the backwater, we found the coarsest particles at the downstream end for the Podzol and Ferralsol, indicating possible bedload movement in addition to the deposition/entrainment processes that dominate supercritical flow. The type of flow therefore affects the size distribution as well as the amount and efficiency of sediment deposition in front of vetiver hedges.
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Copyright Statement Copyright remains with the authors 2007 Griffith University. This is the author-manuscript version of this paper. It is posted here with permission of the copyright owners for your personal use only. No further distribution permitted.
Volume 71
Issue Number 5
Page from 1516
Page to 1523
ISSN 0361-5995
Date Accessioned 2007-06-26
Language en_AU
Research Centre Environmental Futures Research Institute
Faculty Faculty of Science, Environment, Engineering and Technology
Subject PRE2009-Applied Hydrology (Drainage, Flooding, Irrigation, Quality, etc.)
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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