Underwater innovation at Illinois Beach State Park to help mitigate coastal erosion

Aerial view of fully installed submerged rubble ridges
Aerial view of fully installed submerged rubble ridges

Each year, winter wreaks havoc on Lake Michigan communities as waves and ice pummel the coast. In recent years, winter storms combined with record high lake levels have been especially damaging. Illinois Beach State Park (IBSP), which is home to the largest stretch of natural shoreline in Illinois, has been especially hard hit, losing valuable roads, dune ecosystems, and beaches.

US Army Corps of Engineers placing stone offshore of Hosah Park in Zion, IL
US Army Corps of Engineers placing stone offshore of Hosah Park in Zion, IL

This past summer, with funding from the EPA Great Lakes Restoration Initiative, a US Army Corps of Engineers crane carefully placed over 10,000 tons of stone five hundred feet offshore of IBSP and Hosah Park, a Zion Park District property wedged between the north and south units of IBSP.  Hidden from view underneath the shallow coastal waters of Lake Michigan, these stones form three “rubble ridges” approximately seven hundred and fifty feet long. They are intended to work in concert to lessen storm waves and protect the eroding beach and unique terrestrial ecosystem in the dunes while preserving views and enhancing fish habitat.

Since 2014, record lake levels have accelerated erosion across the Great Lakes, necessitating the development of new, lower impact, and less expensive measures that can protect shorelines. In the last six years, Illinois Beach State Park has experienced record high erosion along its shore. The park, home to unique prairie and wetland habitat and a beloved local and regional recreation draw, is threatened by high waters and storm overwash that erode and fill in the narrow dune swales– called pannes– home to rare and endemic plants and animals. A group of scientists led by Steve Brown and Robin Mattheus of the Illinois State Geological Survey, and Ethan Theuerkauf of Michigan State University, have worked to document and understand these changes.

To build on this work, the IDNR Coastal Management Program enlisted help from Healthy Port Futures, a design-research group funded by Great Lakes Protection Fund, to investigate innovative coastal resilience projects in the Great Lakes. The team collaborated with the Shoreline Management Working Group and other local stakeholders, including IDNR Fisheries and Illinois Natural History Survey scientists, who provided guidance to ensure the rubble ridges provide good fish habitat by creating small, protected pore spaces within the structures. Consulting firm Anchor QEA provided engineering expertise throughout the process, including the development of a wave model to calibrate the rubble ridge concept to local environmental conditions.

Fish swimming among the submerged rubble ridges
Early monitoring data has shown fish already utilizing the rubble ridges for habitat

Researchers from Illinois State Geological Survey, Michigan State, and Illinois Natural History Survey will monitor how efficiently the rubble ridges slow waves, their effect on the adjacent beach and nearshore environment, as well as their ability to support fish habitat over time. If successful, the approach will help protect Illinois beaches and may provide a low-cost alternative for other Great Lakes communities looking to protect their coastal landscapes and enjoy the fishing, birding, and beauty these important landscapes offer. This project represents an important step towards the future of Great Lakes coastal resiliency and is a testament to the importance of interagency collaboration, a reliance on good science, and an investment in developing innovative approaches that preserve the most basic and important qualities and experiences of places Illinoisans love.

Rendering of project plan describing protected beach, dissapated wave zone, submerged rubble ridge, and prevailing wave direction
Rendering of project plan