Exploring the Effects of Density and Configuration on Wave Attenuation through Mangrove Living Shorelines

A 1:10 geometric scale physical model was constructed in the United States Naval Academy (USNA) Coastal Basin to evaluate the effectiveness of mangrove trees and other rigid vegetation in attenuating waves. A temporary flume was set up in the Coastal Basin tank. To test the different configurations of different model densities, a PVC base plate was manufactured with 90 holes of a set diameter set up in an array with up to 15 rows of specimens, with 6 specimens per row. Six different configurations, ranging from a full configuration containing 90 models to an empty configuration containing 0 models, were tested. Wave heights of 2.54 cm, 3.81 cm, and 5.08 cm were run at five different wave periods of 1.0 s, 1.15 s, 1.30 s, 1.45 s, and 1.60 s, and water surface elevations were measured immediately before and after the model configurations. The average transmission coefficient was calculated for each trial to assess wave height attenuation. Results show that wave heights were attenuated by up to 65%. In general, the denser the vegetation is planted and the more rows of vegetation that are planted, the more effective a living shoreline design will be at protecting the coastline behind the living shoreline.