Effect of Floodplain Non-submerged Vegetation on Bed Variation in Meandering Compound Rivers

Document Type : Research Article

Authors

1 Shiraz University

2 Water Engineering, Shiraz University

Abstract

Scouring and variations of bed topography in meandering river is one of the most interesting issues in river engineering. Vegetation is a significant feature of rivers. Various studies have shown that the presence of vegetation may have an important impact on flow field and river morphology. Due to the complex geometry and hydraulics of flow in natural rivers, physical or mathematical models are often useful to evaluate morphological variations. The purpose of the present study is to investigate the morphological changes in alluvial meandering rivers with compound cross section to gain insight into the physical processes involved. Hence, the bed topography in an alluvial meandering asymmetric compound channel is assessed with vegetated and non-vegetated floodplain conditions. Cylindrical rods of 10 mm diameter were used to simulate rigid vegetation. The rods were installed over the floodplain in two parallel patterns with one row and two rows of vegetation, respectively. The results showed that the point of maximum scour depth was located near the outer bank. Due to high flow velocity entering the bend, the scour depth at section entrance of the bend was greater than other sections. Also, the thalwege was moved away from the interface after planting the vegetation.

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Main Subjects

References

[1]. Ministry of Energy. Guideline on Hydraulic Geometry and Channel Pattern of Rivers. 2013; No. 643. (In Persian).
[2]. Watershed Management Deputy. Basic Design for Erosion Control in Streams and Channels Structures. (In Persian). 2008; No. 417.
[3]. Farrady RV, Charlton FG. Hydraulic factors in bridge design, Hydraulic Research station Limited, Wallingford, Oxford shire, London, England. 1983.
[4]. Fazli M, Ghodsiyan M, Salehi Neyshabori SA. Study scouring around groins in river bends, 3th civil engineering conference, Tabriz. (In Persian). 2008.
[5]. Abad JD, Garcia MH. Experiments in a high-amplitude kinoshita meandering channel: implications of bend orientation on mean and turbulent flow structure. Water Resour. Res. 2009; 45: 1–19.
[6]. Chen D, Tang C. Evaluating secondary flows in the evolution of sine-generated meanders. Geomorphology. 2012.
[7]. Engel FL, Rhoads BL. Interaction among mean flow, turbulence, bed morphology, bank failures and channel plan form in an evolving compound meander loop. Geomorphology. 2012.
 
[8]. Esfahani F, Keshavarzi A. Effect of different meander curvatures on spatial variation of coherent turbulent flow structure inside ingoing multi-bend river meanders. Stochastic Environ. Res. Risk Assess. 2011; 25: 913-928.
[9]. Keshavarzi A, Hamidifar H, Ball J. Bed morphology in vegetated estuarine river with mild-curved meander bend. Hydrol. Sci. J. 2016; 61(11):2033-49.
[10].            Esfahani F, Keshavarzi A. How far must trees be cultivated from the edge of the flood plain to provide best river bank protection?. International Journal of River Basin Management. 2010; 8(1): 109-116.
[11].            Yang K, Cao S, Knight DW. Flow patterns in compound channels with vegetated floodplains. Journal of Hydraulic Engineering. 2007; 133: 148-159.
[12].            Weiming W, Douglas J, Bennett S, Wang S. A depth-averaged two-dimensional model for
flow, sediment transport, and bed topography in curved channels with riparian vegetation. Water Resour. Res. 2005; 41: W03015.
[13].            Keshavarzi A, Hamidifar H, Ball J. Bed morphology in vegetated estuarine river with mild-curved meander bend. Hydrol. Sci. J. 2016; 61(11): 2033-2049.
[14].            Hamidifar H, Omid MH, Keshavarzi A. Evaluation of 1-D and 2-D model for discharge prediction in straight compound channel with smooth and rough floodplain. Flow Measurment and Instrumentation, 2016; 49: 63-69.
[15].            Hamidifar H, Keshavarzi A, Saadatnia M, Sistani B. Experimental investigation of the effect of pile installation on change of erosion and sedimentation pattern in channel’s meander. 7th Iranian Hydraulic Conference, Tehran, Iran. 2008.
[16].            Yalin MS. River Mechanics. Pergamon Press: London. 1992.
Iranian journal of Ecohydrology
Volume 5, Issue 2
July 2018
Pages 461-470

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History

  • Receive Date: 22 June 2017
  • Revise Date: 20 September 2017
  • Accept Date: 06 October 2017
  • First Publish Date: 22 June 2018
  • Publish Date: 22 June 2018

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