Wave transmission and reflection by trees and porous structures in coast area
Kenjirou Hayashi, Tuyoshi Tada, Kuniaki Oi, Yoshihisa Miyata
Friday 3 july 2015
9:15 - 9:30h
at North America (level 0)
Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology
Parallel session: 14F. Environment - Ecohydraulic
Concrete blocks and stones are commonly used for banks in rivers and breakwaters in coasts. These conventional materials are effective in protecting against coming currents and waves. On the other hand, banks and breakwaters covered with these materials are not so good from environmental and recreational points of view. Laboratory experiments were performed to study wave transmission and wave reflection capacity of circular cylinders, modeling trees and porous structures near the coast as coastal protection from wind waves and tsunamis. The energies dissipated in the array of circular cylinders were evaluated by measuring the drag forces acting on them and wave particle velocities of incident waves. The drag forces acting on a circular cylinder are measured by using a multi component load cell. The wave particle velocities are measured by using a Laser Doppler anemometer. A theoretical and numerical analysis based on application of the continuity and energy equations to flow through the rows of circular cylinders were made to evaluate wave transmission and wave reflection capacity in the array of circular cylinders. The reflection coefficient Kr is significant for large value of the ratio of the circular cylinders area to the unit bed area in the array of circular cylinders. These theoretical and numerical analysis were also made to evaluate wave transmission and wave reflection capacity of mangroves and break water using concrete blocks in coastal area. The significant wave reflection from mangroves with dense canopy was estimated.
