Ranjit S Jadhav, Qin Chen


Wave data were measured along a 28 m transect using 3 pressure transducers over a 2-day period during a tropical storm. The tropical storm force winds produced waves up to 0.4 m high (zero-moment) that propagated over vegetation of Spartina alterniflora submerged under a surge of over 1 m above the marsh floor. Measured wave heights, energy losses between gages and spectral energy dissipation models of rigid vegetation were utilized to estimate wave height decay rates, integral and frequency-dependent bulk drag coefficients, and frequency distribution of energy dissipation induced by the vegetation. Measurements showed that incident waves attenuated exponentially over the vegetation. The exponential wave height decay rate decreased as Reynolds number increased. The swell was observed to decay at a slower rate than the wind sea regardless of the wave height. The linear spatial wave height reduction rate increased from 1.5% to 4% /m as incident wave height decreased. The bulk drag coefficient estimated from the field measurement decreased with increasing Reynolds and Keulegan-Carpenter numbers. The energy dissipation varied across the frequency scales with the largest magnitude observed near the spectral peaks, above which the dissipation gradually decreased. The wave energy dissipation did not linearly follow the incident energy, and the degree of non-linearity varied with the frequency. For a given spectrum, the frequency-distributed drag coefficient increased gradually up to the peak frequency and remained approximately at a stable value at the higher frequencies. This spectral variation was parameterized by introducing a frequency-dependent velocity attenuation parameter inside the canopy. The spectral drag coefficient is shown to predict the distribution of energy dissipation with more accuracy than the integral coefficients, which results in a more accurate prediction of the mean wave period and spectral width of a wave field with vegetation.


salt marsh; vegetation; bulk drag coefficient; random waves; wave attenuation; energy dissipation; tropical cyclone


Anderson, M. E., J. M. Smith, and S. K. McKay. 2011. Wave Dissipation by Vegetation. Coastal and Hydraulics Engineering Technical Note ERDC/CHL CHETN-I-82. U.S. Army Engineer Research and Development Center, Vicksburg, MS.

Asano, T., H. Degushi, and N. Kobayashi. 1993. Interaction between water wave and vegetation, in Proceedings of 23rd International Conference on Coastal Engineering, pp. 2710–2723, ASCE, New York, NY.

Augustin, L. N., J. L. Irish, and P. J. Lynett. 2009. Laboratory and numerical studies of wave damping by emergent and near-emergent wetland vegetation, Coastal Eng., 56, 332–340.

Bendat, J. S., and A. G. Piersol. 2000. Random data: analysis and measurement procedures, John Wiley and Sons, Inc. New York, NY.

Borsje, B. W., B. K. van Wesenbeeck, F. Dekker, P. Paalvast, T. J. Bourma, M. M. van Katwijk, and M. B. de Vries. 2011. How ecological engineering can serve in coastal protection, Ecol. Eng. 37 (2), 113–122.

Bradley, K., and C. Houser. 2009. Relative velocity of seagrass blades: Implications for wave attenuation in low energy environments, J. Geophys. Res., 114, F01004, doi:10.1029/ 2007JF000951.

Chen, Q, and H. Zhao. 2012. Theoretical models for wave energy dissipation caused by vegetation, J. Engineering Mech., 138(2), 221-229.

Cox, R., S. Wallace, and R. Thomson. 2003. Wave damping by seagrass meadows, in Proceedings of 6th International COPEDEC Conference. Lanka Hydraulic Institute, Colombo, Sri Lanka, Paper No 115.

CPRA. 2012. Louisiana's Comprehensive Master Plan for a Sustainable Coast. Coastal Protection and Restoration Authority of Louisiana. Baton Rouge, LA.

Dalyrmple, R. A., J. T. Kirby, and P. A. Hwang. 1984. Wave refraction due to areas of energy dissipation, J. Waterw. Port Coastal Ocean Eng., 110, 67–79.

Dixon, A. M., D. J. Leggett, and R. C. Weight. 1998. Habitat creation opportunities for landward coastal re-alignment: Essex case study. J. Chartered Institution of Water and Environmental Management, 12, 107–112.

Dubi, A., and A. Tørum. 1996. Wave energy dissipation in kelp vegetation, in Proceedings of the 25th International Conference on Coastal Engineering, pp. 2626-2639, ASCE, New York, NY.

Gedan, K. B., M. L. Kirwan, E. Wolanski, E. B. Barbier, and B. R. Silliman. 2011. The present and future role of coastal wetland vegetation in protecting shorelines: an answering recent challenges to the paradigm. Climatic Change, 106, 7-29.

Irish, J. L., L N. Augustin, G. E. Balsmeier, and J. M. Kaihatu. 2008. Wave dynamics in coastal wetlands: a state-of-knowledge review with emphasis on wetland functionality for storm damage reduction, Shore and Beach, 76, 52–56.

Jadhav, R.S., and Q. Chen. 2012. Wave attenuation by salt marsh vegetation during tropical cyclone, J. Geophys. Res., submitted.

Jadhav, R.S., Q. Chen., and J.M. Smith. 2012. Spectral distribution of wave energy dissipation by salt marsh vegetation, Coastal Eng, submitted.

Kobayashi, N., A. W. Raichlen, and T. Asano. 1993. Wave attenuation by vegetation, J. Waterw. Port Coastal Ocean Eng., 119, 30–48.

Lopez, J.A. 2009. The Multiple Lines of Defense Strategy to Sustain Coastal Louisiana, J. Coastal Res.: Special Issue 54 - Geologic and Environmental Dynamics of the Pontchartrain Basin [FitzGerald & Reed]: pp. 186 – 197.

Løvås, S.M., and A. Tørum. 2001. Effect of kelp Laminaria hyperborea upon sand dune erosion and water particle velocities, Coastal Eng., 44, 37–63.

Lövstedt, C.B., and M. Larson. 2010. Wave damping in reed: Field measurements and mathematical modeling. J. Hyd. Eng., 136(4), 222-233.

Lowe, R. J., J. R. Koseff, and S. G. Monismith. 2005. Oscillatory flow through submerged canopies: 1.Velocity structure, J. Geophys. Res., 110, C10016, doi:10.1029/2004JC002788.

Lowe, R., J. Falter, J. Koseff, S. Monismith, and M. Atkinson. 2007. Spectral wave flow attenuation within submerged canopies: Implications for wave energy dissipation, J. Geophys. Res., 112, C05018, doi:10.1029/2006JC003605.

Mendez, F. J., and I. J. Losada. 2004. An empirical model to estimate the propagation of random breaking and non-breaking waves over vegetation fields, Coastal Eng., 51, 103–118.

Möller, I., T. Spencer, J. R. French, D. Leggett, and M. Dixon. 1999. Wave transformation over salt marshes: a field and numerical modelling study from North Norfolk, England, Estuarine Coastal Shelf Sci., 49, 411–426.

Möller, I., and T. Spencer. 2002. Wave dissipation over macro-tidal salt marshes: effects of marsh edge typology and vegetation change, J. Coast. Res., SI36, 506–521.

Möller, I. 2006. Quantifying salt marsh vegetation and its effect on wave height dissipation: results from a UK East coast saltmarsh, Estuarine Coastal Shelf Sci., 69, 337–351.

Mullarney, J.C., and S.M. Henderson. 2010. Wave forced motion of submerged single stem vegetation, J. Geophys. Res., 115, C12061, doi:10.1029/2010JC006448.

Paul, M., and C. L. Amos. 2011. Spatial and seasonal variation in wave attenuation over Zostera noltii, J. Geophys. Res., 116, C08019, doi:10.1029/2010JC006797.

Riffe, K. C., S. M. Henderson, and J. C. Mullarney. 2011. Wave dissipation by flexible vegetation, Geophys. Res. Lett., 38, L18607, 5 pp., doi:10.1029/2011GL048773

Smith, J. M., R. E. Jensen, A. B. Kennedy, J. C. Dietrich, and J. J. Westerink. 2011. Waves in wetlands: Hurricane Gustav, in Proceedings of the 32nd International Conference on Coastal Engineering.

Stratigaki, V., E. Manca, P. Prinos, I. J. Losada, J. L. Lara, M. Sclavo, C. L. Amos, I. Cáceres and A. Sánchez-Arcilla. 2011. Large-scale experiments on wave propagation over Posidonia oceanica, J. Hydraulic Res., 49, sup1, 31-43.

Suzuki, T., M. Zijlema, B. Burger, M. C. Meijer, and S. Narayan. 2011. Wave dissipation by vegetation with layer schematization in SWAN, Coastal Eng., 59, 64-71.

Tanino, Y., and Nepf, H. M. 2008. Laboratory investigation of mean drag in a random array of rigid, emergent cylinders, J. Hydraul. Eng., 134, 1, 34–41.

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