Laboratory Measurements of Wave Attenuation through Model and Live Vegetation

Surge and waves generated by hurricanes and tropical storms often cause severe damage and loss of life in coastal areas. It is widely recognized that wetlands along coastal fringes reduce storm surge and waves. Yet, the potential role and primary mechanisms of wave mitigation by wetland vegetation are not fully understood. Knowledge of wave attenuation is essential for assessing the ability of vegetation to limit wave damage. The goal of the work reported here was to use a laboratory wave flume to quantify the attenuation of waves as a function of vegetation type, density, and height. The properties of waves passing through rigid and flexible model vegetation as well as live Spartina alterniflora and Juncus romerianus were measured. An automated system was developed and used to generate regular and random waves and to record time series of water surface elevation. A technique was developed for extracting the water surface profile through the vegetation field from images recorded with a consumer grade digital video camera. The new method was also tested for wave setup measurements along a plane sloping beach.