Living Docks: Structural Implications and Determination of Force Coefficients of Oyster Mats on Dock Pilings in the Indian River Lagoon

Abstract

Brevard County, Florida, is facing rapid population growth and increased pollution entering the Indian River Lagoon (IRL), impairing water quality and damaging the ecosystem. This is problematic not only for public health and environmental stability, but also for the economy. The Living Docks initiative was created to combat environmental degrade in the lagoon and restore natural functions back to the ecosystem. With increased urbanization along coastal systems, there is opportunity for new forms of ecological engineering such as Living Docks, which attaches oyster mats to dock pilings as a means to promote the growth of filter feeding organisms. It is expected that with the addition of oyster mats and biofouling, the forces on the dock piling will increase. In order to analyze the structural effect of the oyster mats as part of Living Docks, a scale model was tested in the Florida Institute of Technology’s wave tank. The three main objectives of this study were to: (1) measure forces from a scaled down simulation in a wave tank by use of a strain gauge, (2) determine drag and inertia coefficients from conditions expected in the IRL, and (3) compare calculated forces of Living Docks in the IRL to national design standards. Three phases were tested: a plain piling (phase 1), a piling with a freshly deployed oyster mat (phase 2), and a piling with an oyster mat that has accumulated four months of biofouling (phase 3). Results proved there is approximately a 75% increase in forces by adding an oyster mat to a dock piling, and a 115% increase from a bare piling to one with significant growth. The force coefficients were determined 𝐶𝑑 = 1.31 and 𝐶𝑚 = 1.01 which can be applied to future designs in any location. There was no indication of hazardous effects on the host dock piling proving Living Docks is a safe and reliable restoration effort that can be easily implemented with any dock.