Oyster Shellters: Ecologically Enhanced Concrete Sea Walls

Joseph Johnston, Taubman College of Architecture + Urban Planning

Collaborator: Yunyang Ma, Taubman

Faculty Advisors: Wes McGee, Associate Professor of Civil Engineering and Architecture; Tszyan Ng: Associate Professor of Architecture

Our proposal investigates how concrete can create a symbiotic relationship between people and marine life, simultaneously making coastal communities more resilient to the effects of climate change and increasing the diminishing biodiversity in our oceans. Seawalls in coastal communities play an important role in the threshold of land, private and public, and oceans, which are rising and becoming more volatile due to climate change.

Our project looks to design a sea wall facade system that can promote oyster growth at the base under water and sea grass at the top of the system. This living system can work to naturally fortify the seawall construction, while increasing the biodiversity of the hard coastline barrier.

The Ocean Living Planet Index indicates that the global ocean fish stocks were over-exploited by 29%, ocean species declined by 39% and the world coral reefs decreased by 50% (Byomkesh et al., 2022). These trends result from anthropogenic causes like overfishing and from effects of climate change such as ocean acidification and warming temperatures.

The Reef Ball Foundation paved the way for using concrete to create artificial reef structures for oysters and fish to inhabit. Uddin, Smith, and Hargis developed a concrete mixture called POSH that proves to be superior for cost, durability, environmental benefits, and carbon footprint of different materials for reef restoration. (Uddin et al., 2021) Concrete has also been proven to be an effective protection against tidal energy impacts and flooding.

Evidence that vessel wake stress is driving ecosystem loss and living shoreline structures designed to reduce this energy can slow or reverse ecosystem decline. (Safak et al., 2020) The sea wall facade system is proposed to be designed in 3 parts each with their own unique design and hierarchies.

The upper section will be designed to promote sea grass growth as a final flood protection barrier between the water and the home. The middle section will be the vertical section that is exposed on the upper part of the seawall, which will be designed with a modular system that prioritizes aesthetics and ease of disassembly.

The bottom section that is submerged under water will be designed with a minimum surface grasshopper code that reinforces the structural integrity of the system, while providing enough surface area and shelter, through the apertures in the structure, to promote oyster growth and fish inhabitation.

The finishing of the concrete may also play a role in the function of this section. The potential of using crushed oyster shells as aggregate and using the exposed aggregate finishing technique to promote oyster growth is something that will be studied further. These elements explore the intersection of engineering, design, and biology and will work together to create a more resilient and biodiverse shoreline for coastal communities.

The outcome of this project will be a 1:1 scale prototype of this sea wall system to be completed as part of our thesis with Professors Tszyan Ng and Wes McGee by the end of April. This funding will help us source materials to build the prototype and specialized tools like industrial grinders for the crushing of the oyster shells for the concrete mix, giving us integral experience in the realization of a design research idea into a built prototype.