316 - Examining the Influence of Intertidal Eastern Oyster (Crassostrea virginica) Reefs on Local Hydrodynamics in Shallow Water

Recognizing the benefits of natural oyster reefs to stabilize shorelines, created oyster reefs have become popular alternatives to traditional breakwater structures in shallow water. However, designs of living breakwaters are hindered by a lack of data that can indicate the expected range of energy attenuation from structures and that also can support live shellfish canopies. This study’s objective is to investigate the influence of intertidal oyster reefs on local hydrodynamics over tidally and seasonally variable water levels. Field investigations were conducted in the vicinity of healthy, live natural oyster reefs in Mosquito Lagoon, a microtidal estuary on the Atlantic coast of Florida. Two studied reefs are intertidal with one in front of another from the channel, but vary in morphology (dimension, shape, and height), oyster canopy characteristics (density and rugosity), and path of the incident flow. The cumulative effect of multiple reef patches is compared to a single reef patch. Flow velocity, water depth, and wave height were collected to simultaneously characterize incident flows and flows affected by reefs during rising tides over various seasonal water levels. Changes to bed elevations in the reef vicinity were tracked periodically. Initial results indicate that the front reef attenuated the majority of wave energy from the channel. Maximum incident significant wave heights of 7.5 cm were observed in the channel but decreased to 3.4 cm in the front and 2.6 cm behind the front reef. The back reef exhibited different results with minimal wave height attenuation. Results from the study can be helpful for practitioners in choosing appropriate locations for emplacing created oyster structures to achieve maximum effect in shoreline protection via wave attenuation, oyster recruitment, and oyster growth.