MODELING WAVE DAMPING AND SEDIMENT TRANSPORT WITHIN A PATCH OF VEGETATION

Gangfeng Ma

Abstract


Vegetation canopies control mean and turbulent flow structures as well as suspended sediment processes in the coastal wetlands. In this study, a three-dimensional hydrodynamic and sediment transport model is developed for studying flow/wave-vegetation-sediment interactions. The model is based on the non-hydrostatic model NHWAVE. The vege- tation effects on turbulent flow are accounted for by introducing additional formulations associated with vegetation- induced drag and turbulence production in the governing equations. The sediment concentration is obtained by solving the advection-diffusion equation with sediment exchange at the bed. The turbulent flow and suspended sediment are simulated in a coupled manner. The model is validated against the laboratory measurements of partially vegetated open channel flows. It is shown that the model can well predict the vegetation effects on the flow field. The model is then employed to study nearshore sediment suspension influenced by a patch of vegetation, which is located in the surf zone. The turbulence generated by wave breaking is greatly damped by the vegetation patch, resulting in considerably less sediment pickup from the bottom in the surf zone. Within the vegetation patch, most suspended sediments are restricted in a thin layer near the bottom. The net sediment transport is in the shoreward direction, in contrast to the seaward net transport of sediments in the unvegetated surf zone.

Keywords


NHWAVE; vegetated flow; sediment transport; nearshore sediment flux

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References


Abt S., Clary W., Thornton C., 1994, Sediment deposition and entrapment in vegetated streambeds, J. Irrig. Drain. Eng., 120, 1098–1110

Chen S.-N., Sanford L.P., Koch E.W., Shi F. and North E.W., 2007, A nearshore model to investigate the effects of seagrass bed geometry on wave attenuation and suspended sediment transport, Estuaries and Coasts, 30, 296-310

Dubi A. and Torum A., 1995, Wave damping by kelp vegetation. In edge B.L. (Ed.), Proc. 24th Coast. Eng. Conf., ASCE, New York, 142-156

Elliott A. H., 2000, Settling of fine sediment in a channel with emergent vegetation, J. Hydraulic Eng., 126, 570-577

Gacia E., Granata T.C. and Duarte C.M., 1999, An approach to measurement of particle flux and sediment retention within seagrass (Posidonia oceanica) meadows, Aquatic Botany, 65, 255–268

Gottlieb S., Shu C.-W. and Tadmor E., 2001, Strong stability-preserving high-order time discretization methods, SIAM Review, 43, 89-112

Henderson S.M., Allen J.S. and Newberger P.A., 2004, Nearshore sandbar migration predicted by an eddy-diffusive boundary layer model, J. Geophys. Res., 109, C06024, doi:10.1029/2003JC002137

Lin P. and Liu P.L.-F., 1998, A numerical study of breaking waves in the surf zone, J. Fluid Mech., 359, 239-264

Lopez F. and Garcia M., 1998, Open-channel flow through simulated vegetation: Suspended sediment transport modeling, Water Res. Res., 34 (9), 2341-2352

Ma G., Shi F. and Kirby J.T., 2011, A polydisperse two-fluid model for surf zone bubble simulation, J. Geophys. Res., 116, C05010, doi:10.1029/2010JC006667

Ma G., Shi F. and Kirby J.T., 2012, Shock-capturing non-hydrostatic model for fully dispersive surface wave processes, Ocean Modell., 43-44, 22-35

Ma G., Kirby J.T., Su S.-F., Figlus J. and Shi F., 2013a, Numerical study of turbulence and wave damping induced by vegetation canopies, Coastal Eng., 80, 68-78

Ma G., Kirby J.T. and Shi F., 2013b, Numerical simulation of tsunami waves generated by deformable submarine landslides, Ocean Modell., 69, 146-165

Ma G., Su S.-F., Liu S. and Chu J.-C., 2014a, Numerical simulation of infragravity waves in fringing reefs using a shock-capturing non-hydrostatic model, Ocean Eng., 85, 54-64

Ma G., Shi F., Hsiao S.-C. and Wu Y.-T., 2014b, Non-hydrostatic modeling of wave interactions with porous structures, Coastal Eng., 91, 84-98

Ma G., Chou Y.-J. and Shi F., 2014c, A wave-resolving model for nearshore suspended sediment transport, Ocean Modell., 77, 33-49

Nepf H.M., 1999, Drag, turbulence, and diffusion in flow through emergent vegetation, Water Res. Res., 35 (2), 479-489

Pasche E. and Rouve G., 1985, Overbank flow with vegetatively roughened flood plains, J. Hydraul. Eng., 111, 1262-1278

Rodi W., 1987, Examples of calculation methods for flow and mixing in stratified flows, J. Geophys. Res., 92(5), 5305-5328

Sato S., Homma K. and Shibayama T., 1990, Laboratory study on sand suspension due to breaking waves, Coastal Eng. Jpn., 33, 219-231

Sheng Y.P., Lapetina A. and Ma G., 2012, The reduction of storm surge by vegetation canopies: Three-dimensional simulations, Geophys. Res. Let., 39, L20601, doi:10.1029/2012GL053577

Shi F., Ma G., Kirby J.T. and Hsu T.-J., 2012, Application of a TVD solver in a suite of coastal engineering models, Proc. 33rd Coast. Eng. Conf., ICCE2012, Santander, Spain, July 1-6

Shimizu Y. and Tsujimoto T., 1994, Numerical analysis of turbulent open-channel flow over a vegetation layer using a k-epsilon turbulence model, J. Hydrosci. Hydraul. Eng., 11 (2), 57-67

Sharp R.G. and James C.S., 2006, Deposition of sediment from suspension in emergent vegetation, Water SA, 32, 211-218

Snyder P.J. and Hsu T.-J., 2011, A numerical investigation of convective sedimentation, J. Geophys. Res., 116, C09024, doi:10.1029/2010JC006792

Temmerman S., Bouma T.J., Govers G., Wang Z.B., De Vries M.B. and Herman P.M.J., 2005, Impact of vegetation on flow routing and sedimentation patterns: Three-dimensional modeling for a tidal marsh, J. Geophys. Res., 110, F04019, doi:10.1029/2005JF000301

Thornton C. I., Abt S. R., and Clary W. R., 1997, Vegetation influence on small stream siltation, Journal of The American Water Resource Association, 33, 1279–1288

van Rijn L.C., 1984, Sediment pick-up function, J. Hydraul. Eng., 110,1494-1502

Wang X.H., 2002, Tide-induced sediment resuspension and the bottom boundary layer in an idealized estuary with a muddy bed, J. Phys. Oceanogr., 32(11), 3113-3131

Wang X.H. and Pinardi N., 2002, Modeling the dynamics of sediment transport and resuspension in the Northern Adriatic Sea, J. Geophys. Res., 107(C12), 3225, doi:10.1029/2001JC001303

Wu W., Shields D. Jr., Bennett S.J. and Wang S.S.Y., 2005, A depth-averaged two-dimensional model for flow, sediment transport, and bed topography in curved channels with riparian vegetation, Water Res. Res., 41, W03015, doi:10.1029/2004WR003730

Zhu J., 1991, A low-diffusive and oscillation-free convection scheme, Comm. Appl. Num. Meth., 7, 225-232

Zong L. and Nepf H., 2010, Flow and deposition in and around a finite patch of vegetation, Geomorphology, 116, 363-372

Zong L. and Nepf H., 2011, Spatial distribution of deposition with a patch of vegetation, Water Res. Res., 47, W03516, doi:10.1029/2010WR009516




DOI: https://doi.org/10.9753/icce.v34.sediment.17