THE IMPACT OF DISSIPATION BY VEGETATION ON MEAN WATER LEVEL

Recently, natural and nature-based features have been con- sidered a preferable alternative to conventional risk reduc- tion engineering projects. Efforts to develop a method of predicting wave attenuation in a practical way have been encumbered by complexities of wave-vegetation interaction and the detailed vegetation characteristics. Coastal storm hazards are typically characterized by large waves and elevated water levels. Wave energy attenua- tion by vegetation, doubtlessly, reduces the direct threat of waves with lower runup and storm-driven erosion. On the other hand, the impact of highly dissipative vegetation on the elevated water levels, or storm surge, is more complex and uncertain. The effort outlined herein investigates the component of setup owing to the the forces on vegetation, making use of detailed laboratory measurements. Estimates of bottom friction and vegetation drag coefficients are directly com- puted with an energy balance using measured velocities and wave height decay. The momentum equation, including the calibrated steady force exerted by the vegetation, is inte- grated to estimate mean free-surface and compared with laboratory measurements, highlighting the relative impor- tance of the forces on vegetation and wave radiation stress.