Skip to main content
ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #325550
Title: Laboratory and field investigations of wave attenuation by live marsh vegetation

Author
item WU, WEIMING - Clarkson University
item OZEREN, YAVUZ - University Of Mississippi
item CHIN, QIN - University Of Louisiana
item JADHAV, RANJIT - Ftn Associates, Ltd
item Wren, Daniel

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/9/2016
Publication Date: 5/11/2016
Citation: Wu, W., Ozeren, Y., Chin, Q., Jadhav, R., Wren, D.G. 2016. Laboratory and field investigations of wave attenuation by live marsh vegetation. Proceedings of the 6th International Conference on the Application of Physical Modeling in Coastal and Port Engineering and Science (Coastlab16). Proceedings online (http://rdio.rdc.uottawa.ca/publications/coastlab16/coastlab7.pdf); Ottawa, Canada, May 10-13, 2016. pp 1-10.

Interpretive Summary: Surge and waves generated by hurricanes and other severe storms can cause devastating damage of property and loss of life in coastal areas. Vegetation in wetlands, coastal fringes and stream floodplains can reduce storm surge and waves while providing ecological benefits and complementing traditional coastal defense approaches such as permanent levees, seawalls and gates. However, how to quantify surge and wave reduction needs more investigations. To understand and quantify the attenuation of waves by live marsh vegetation, a series of laboratory experiments and field observations were conducted. Two marsh vegetation species commonly distributing along the U.S. coastlines were selected. A large number of data were collected to develop formulas for the drag coefficient of the tested species. The main result of this study is a formula that can be used to obtain the drag coefficient for the marsh grass species over a range of wave conditions. The drag coefficient is important for use in models that are used to predict the height of waves that pass over coastal marsh area. The wave height can then be used to help predict how far inland the waves can go.

Technical Abstract: Wave attenuation by live marsh vegetation was investigated experimentally in this study. Laboratory experiments were conducted in a 20.6 m long, 0.69 m wide and 1.22 m deep wave flume under regular and random waves. The vegetation species used are Spartina alterniflora and Juncus roemerianus, which widely exist along the U.S. coastlines. Field measurements were conducted under high-energy conditions during a tropical storm at a salt marsh in Terrebonne Bay on the Louisiana coast of the Gulf of Mexico. The field site was dominated by S. alterniflora. The wave attenuation data were compared against an analytical model, and the bulk drag coefficient of vegetation was then calibrated in each experiment run. The drag coefficient of S. alterniflora is found to be a function of the Keulegan-Carpenter number, whereas the drag coefficient of J. roemerianus is closely related to the Keulegan-Carpenter number and vegetation submergence (ratio of vegetation height and water depth). The importance of submergence for J. roemerianus is due to that its stem diameter and density vary along elevation. It is recognized that the data using regular and random waves collapse into single relation for each species by using significant wave height and peak wave period as the representative parameters in the Keulegan-Carpenter number.