4 minute read
Illinois Beach State Park
Zion, Illinois, United States
Using an innovative approach to address coastal erosion. Erosion threatens rare habitat in the Illinois Beach State Park’s (IBSP’s) unique beach-ridge geology. In response to the ongoing challenges of coastal erosion along the northern areas of the IBSP coastline, the Illinois Department of Natural Resources (IDNR) and the Healthy Port Futures Initiative (funded by the Great Lakes Protection Fund) codeveloped rubble ridges for coastal protection and habitat creation. Construction was funded by the Great Lakes Restoration Initiative through grant funding available to IDNR and completed by the U.S. Army Corps of Engineers (USACE). As a series of underwater ridges constructed of smaller stones, the feature is designed to reduce wave energy before it reaches the shore and induces further erosion. As a collection of features, the ridges work together to roughen the lakebed and encourage waves to break offshore. This new lakebed is also designed to serve as fish habitat, offering rocky shelter in an environment that has very little. Because it is a novel pilot project, there are many unknowns regarding final performance, but initial findings are positive. This pilot project showcases the continued need for similarly experimental projects that further the ability to work more productively and collaboratively with coastal processes.
Article Cover: Rubble ridges protecting the habitat of Illinois Beach State Park. (Photo by Healthy Port Futures)
Producing Efficiencies
As a pilot project, the rubble ridges were not overtly motivated by operational efficiency. That said, at the project outset, several considerations aimed to streamline construction. Most obvious was the use of smaller stones than would be typical of an offshore breakwater, making sourcing and transport somewhat easier. In addition, these stones were more casually dumped to form the features (as opposed to being meticulously placed and fit together, as would be the case in a traditional breakwater) in a process that would save time during construction.
Using Natural Processes
At IBSP, the natural processes are actually causing the problematic erosion and longshore sediment transport. Most engineering responses would attempt to halt this, but this approach tends to produce a wide range of collateral effects, both known and unknown. The rubble ridges are designed to simply slow these processes and encourage positive work. Sand continues to move, but in an offshore ridge of slowly moving sediment created by the lower-energy area between the ridges and the shore, providing another barrier to wave energy.
Broadening Benefits
The rubble ridges protect the ecological, cultural, and economic value of IBSP as a rare coastal habitat, a public landscape, and a popular tourism destination. They serve as an accessible habitat for various fish species, as they can swim over and around the ridges in a way that would be impossible with a standard breakwater. The rubble ridges are also intended to remain underwater at most, if not all, water levels. This allows IBSP to serve its cultural role as a public landscape affording beautiful views of Lake Michigan and its infinite horizon, which would be marred by traditional offshore structures.
Promoting Collaboration
The rubble ridge project was the product of a strong collaboration between the IDNR and Healthy Port Futures. The IDNR team conducts robust outreach programs that organize stakeholders around issues of coastal management, including what is known as the “sand-management working group.” It was with the help of IDNR that the project focused on addressing the concerns of partners and incorporated local feedback. For its efforts, the project (as part of the larger Healthy Port Futures Initiative and supported by Anchor QEA) received an Honor Award from the American Society of Landscape Architects in 2020 under the category of Analysis and Planning.
