A Study of Wave Attenuation Through Vegetation

The importance of vegetation in coastal environments is becoming more widely acknowledged. The intricate structure of roots, stems, and canopies of vegetation allows it to absorb external disturbances such as waves and currents. Even though several physical models have been performed, they mostly address the attenuation of regular waves. The influence of wave parameters on vegetation-induced wave height attenuation is not well explored. At the Delft University of Technology, a laboratory mimicking the processes of wave reduction through cylinders was performed. Various tests were carried out, including regular, irregular, broken, and non-broken waves. Moreover, a model imitating the test was built in a non-hydrostatic wave-flow model SWASH, using experimental data to calibrate and validate. The results suggest that the wave attenuation processes inside vegetation strongly depend on the wave characteristic. The numerical model captured very well the processes of the wave height reduction measured in the physical tests. Thus, the rate of wave attenuation was studied as a function of the number of wavelengths and the Ursell number.