WAVE TRANSFORMATION THROUGH SUBMERGED RIGID AND FLEXIBLE VEGETATION PATCHES

Abstract

The energy of coastal waves and storm surges are reduced by vegetation cover, which also helps to maintain wetlands through increased sediment deposition. Coastal regions are becoming more vulnerable to natural disasters, flooding resulting from hurricanes and other extreme storm events is a prominent risk along the coasts. Thus, understanding the effect of vegetation on the hydrodynamic impact of such waves on the coastal structures has become an important issue among the coastal engineeri community. This has created a need for research into the properties of waves passing through wetland vegetation. The physical studies were carried out in the present study with rigid vegetation simulating the mangroves and flexible vegetation simulating the marshy vegetation. Experiments were conducted with regular waves of predefined amplitude and frequency on a horizontal and 1:20 bed slope with constant water depth of 0.47m. One of the key parameters to study the hydro-elastic interaction of the flow with the
vegetal stem to represent real-world coastal vegetation is Young’s modulus E. A convenient way to address the single effect of water depth on wave attenuation is to define the relative stem length H/lv. Wave Run-up decreases with relative water depth for different values of H/lv. Darcy’s friction factor f decreases with Reynolds number in range studied up to 3 x 105
. Predictive equations were proposed for Transmission coefficient (KT) and Runup (RU/Hi) for three different vegetation configurations.