Slope and Bottom Friction Impacts on Wave Attenuation from Living Shorelines

Abstract

Living shorelines and other nature-based solutions have become more widely accepted as a cost-effective, multi-functional, and sustainable approach to coastal resilience. However, in spite of growing stakeholder support, a planning-level understanding of the hydrodynamic impact of living shorelines is not well developed. Not only do these features vary in size, shape, and structural characteristics, but the wave environment in which they exist can be quiescent or extreme. In a series of Simulation WAves Nearshore (SWAN) simulations, we investigated the effect of wave period, wave height, slope, living shoreline feature length, and feature friction coefficient on wave attenuation. Results showed that higher wave period, higher wave height, milder slopes, longer feature lengths, and higher feature roughness largely correlated with higher wave attenuation. However, only on mild slopes did additional feature lengths result in appreciable additional attenuation. Characteristic lengths were thus computed to better illustrate the cost-effectiveness of additional feature lengths given a particular wave environment. In this way, regardless of the particularities of individual project sites, planners can better assess potential living shoreline projects before pursuing more detailed, costly analyses.