UN Sustainable Development Goals Addressed
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Goal 9: Industry Innovation & Infrastructure
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Goal 13: Climate Action
2020 Global Design Challenge Finalist
This design concept was developed by participants in the Institute’s Global Design Challenge. The descriptions below are from the team’s competition entry materials.
Location: Boston, MA, United States
Team members: Julia Hostetter, Taylor Furbish, Zach Pierce, Eva Power, Madeline DuBois
Innovation Details
Noting that coastal regions are becoming increasingly vulnerable due to storm intensification and rising sea levels, this team from Northeastern University designed novel seawall retrofits to improve coastal resiliency. Taking inspiration from seagrass and mangroves, this three-part design can be tailored to conditions at a specific location.
What is the problem you are trying to solve and how is it related to the united nations sustainable development goals?
Our team has identified seawalls as a critical piece of infrastructure that has seen little in terms of resilience innovation. With the threat of rising seas and intensification of storms due to climate change, seawalls remain the last threshold of protection between land and ocean. Coastal communities are subjected to increasing annual flooding and erosion, leading to property damage and potential loss of life. Today, 14% of the United States coastline is armored, opening up thousands of miles of coastline for our proposed designs. Our team addressed the Industry, Innovation, and Infrastructure and Climate Action UN Sustainable Development Goals by providing a way to retroactively improve existing coastal protection structures without vertical addition of new concrete. This solution addresses the Industry, Innovation, and Infrastructure goal with a set of novel seawall retrofits to improve coastal resiliency. The default solution to failing seawalls is reconstruction, which has significant associated material costs and environmental impacts. A better alternative is retrofitting, which can extend the design life of these existing structures more sustainably and affordably. There is a significant potential financial return on developing a system that preserves structures that are failing. The retrofit design ties into Climate Action by allowing communities with limited infrastructure budgets to better respond to two key threats posed by climate change: storm intensification and sea level rise.
What organisms/natural systems did you learn from and how did what you learned inform your design?
Our solution is a three-part suite of options which increase the design life of seawalls by individually targeting various aspects that lead to failure. Each physical function was inspired by a different natural system. For wave energy dissipation, our solution is inspired by the pomelo’s system of fluid filled struts that rupture and air pockets that compress to simultaneously absorb impact when falling from a tree. Our solution for the reduction of fluid velocity and turbulence at the seawall face was inspired by Common Eelgrass (Zostera marina), which attenuate wave energy at the seafloor in the natural environment. For sediment transport reduction and establishing an elevated sediment equilibrium profile, our design mimics the structure and function of the network of seagrass rhizomes in the subsurface. Our research and investigation into organisms that perform the functions we desired in different contexts revealed both the strengths and limitations of natural systems. For example, the impact absorption of the pomelo only needs to work once, as the pomelo is not subjected to multiple falls. Our design considered the function of the pomelo, but incorporated a way to utilize the same function repeatedly. Similarly, Common Eelgrass typically cannot survive in a high energy environment due to sediment instability and damage. Our design incorporated the natural technique of eelgrass, reducing fluid velocity with turbulence and drag. We deliberately studied the physics of the eelgrass to shortcut evolution and determine what parameters would be optimized if eelgrass was to live in the environment proposed for our installation. In this way we were able to draw inspiration not just from an existing organism, but the underlying process that generates nature’s efficient, streamlined, and sustainable designs.
What does your design solution do? How does it address the problem or opportunity you selected?
Wave energy impact at the face of the seawall, which causes structural damage and failure, is directly reduced with our first design component Interwoven, closed, partially water-filled tubes absorb wave energy as they are compressed by the incoming wave, and energy is also dissipated as the water in the tubes is forced upwards against gravity and friction. These tubes are most efficiently installed on a seawall with limited structural damage, exposed to significant wave action and low wave frequency. By reducing impact loading on a seawall, this design allows the seawall to survive more intense waves and extends the design life of the wall. The artificial seagrass design relies on drag and micro-turbulences on the blade edges to reduce energy within the fluid. This design features PVC and bamboo tiles that are mounted to the vertical face of the seawall. Two geometries of artificial seagrass blades are included in the design Flat blades with sharp edges rapidly reduce fluid energy by inducing turbulence on the upper section of the seawall. Cylindrical blades closest to the seawall toe reduce turbulence, preventing sediment resuspension and scour, which is erosion at the toe and is one of the leading causes of seawall failure. This design is best utilized on seawalls with low to medium wave energy and high wave frequency that are installed on fine grained sediment susceptible to scour. The mesh design uses subsurface structures to physically stabilize sediment otherwise lost during winter storms, as well as to provide habitat for secreting microorganisms that contribute to sediment stabilization. This design addresses the issue of long-term sediment loss near seawalls and raises the local sediment equilibrium profile, preventing the need for shoreline renourishment or transport disruptive structures.
