Large-Scale Physical Model Study of Wave Overtopping Mitigation by Hybrid Infrastructure

While conventional structural (gray) methods (i.e., bulkheads, revetments) have been implemented to stabilize and protect coastlines, natural (green) and hybrid green-gray solutions have gained attention as effective alternatives that provide engineering services and ecological, economic, and cultural co-benefits that may protect new development or expand the service life of legacy infrastructure near developed coastlines. However, a fundamental lack of understanding of the performance and associated uncertainty of green and hybrid infrastructure limits these systems’ broad implementation. In this proposed project, we conducted a targeted large-scale physical model investigation of wave overtopping of gray, green, and hybrid coastal systems to quantify the hydraulic response of hybrid natural-structural systems. We focused on two system archetypes common to southern Florida: mangrove + bulkhead and mangrove + revetment shorelines. The project leveraged the expertise of nature-based engineering, ecology, and biology domain experts and stakeholders from government, industry, and research through the formation of a Research Coordination and Advisory Network (RCAN), which informed experimental design. We leveraged data from previous field investigations characterizing mangrove geometric and mechanical properties and inherent variability to inform the construction of a large-scale physical model and targeted numerical model simulations. We designed six configurations of a physical model including two forest densities for each system archetype (mangrove + bulkhead and mangrove + revetment) and an unforested configuration for each archetype. We tested each configuration with random, regular, and transient wave regimes. The data allowed us to disaggregate system component effects on hydraulic response (Libby, 2024) and to validate and compare model limits. Fundamental processes affecting wave transformation through these systems will be identified and synthesized to inform the design of these systems for enhanced coastal resilience.