Hydrodynamic differences among shorelines with no vegetation, reference vegetation (mature mangrove), and vegetation planted on restored shoreline (marsh grass and young mangrove) were compared based on field observations 6.5 years after living shoreline restoration. Mean current velocities and waves were more strongly attenuated in vegetation (from channel to shoreline: 80–98% velocity decrease and 35–36% wave height reduction) than in bare shoreline (36–72% velocity decrease, 7% wave height reduction, ANOVA: p < 0.001). Normalized turbulent kinetic energy dissipation rates were significantly higher in reference vegetation (0.16 ± 0.03 m⁻¹) than in restored (0.08 ± 0.02 m⁻¹) or bare shoreline (0.02 ± 0.01 m⁻¹, p < 0.001). Significant differences in the current attenuation and turbulence dissipation rates for the reference and planted vegetation are attributed to the observed differences in vegetation array and morphology. Although the hydrodynamic analyses did not suggest limitations to recruitment, mangrove seedlings were not observed in restored vegetation, while four recruited seedlings/m were counted in the reference vegetation. The lack of recruitment in the restored shoreline may suggest a lag in morphological habitat suitability (slope, sediment texture, organic matter content) after restoration. Although hydrodynamics suggest that the restored site should be functionally similar to a reference condition, thresholds in habitat suitability may emerge over longer timescales.

Preventing shoreline erosion is critically important as coastal hazards intensify. Living shoreline stabilization protects vulnerable coastal assets while promoting biodiversity. However, increased understanding of impacts to physical processes could improve restoration designs. This before-after-control-impact study quantifies hydrodynamic change resulting from restoring a degraded estuarine shoreline using living shoreline techniques. The eroding shoreline, located in Florida’s Mosquito Lagoon, was restored using oyster shell bags and emergent vegetation. Hydrodynamic data were collected from three shoreline sites (the Restored shoreline, a Control degraded shoreline, and a control Reference shoreline stabilized by mature mangroves) before and after living shoreline implementation. We find immediate and pronounced hydrodynamic effects attributed to restoration. Incoming velocities were reduced in the Restored site soon after restoration and significant wave heights were attenuated by the living breakwaters. Notably, onshore-offshore gradients of mean velocities and turbulence statistics within the restored site differed from the reference shorelines.