Large-scale 3-D experiments of wave and current interaction with real vegetation. Part 2: Experimental analysis

Abstract

This paper assesses the influence of different flow and vegetation parameters on the wave attenuation provided by two contrasting salt marsh species: Puccinellia maritima and Spartina anglica. Different water depths and wave parameters (height and period) are considered for both regular and irregular waves with and without an underlying uniform current coming from different directions. The study of the submergence ratio (h/hv) influence shows that wave damping coefficient rapidly decreases as the plant submergence ratio increases. The high nonlinearities found in the wave–current interaction lead to different wave damping patterns in comparison to wave-only conditions. A smaller wave damping is found for waves and current acting in the same direction and an increase in the wave damping rate is obtained for waves and current flowing in the opposite direction. These wave and current tests allow for the studying of the energy dissipation produced by the vegetation, increasing our knowledge about flow and plant interaction in estuarine conditions. The biomechanical properties of the two real salt marshes used in the experiments are also evaluated and related to wave damping revealing a higher attenuation for stiffer vegetation. Both, the vegetation density and the biomass strongly influence wave damping. Higher density and biomass values lead to higher attenuation rates for both species.