Chicago Construction News staff writer
Two projects underway at Illinois Beach State Park will help protect the shoreline from erosion caused by Lake Michigan waves and inform future decisions about how to blunt the effects of erosion and climate change , the Illinois Department of Natural Resources (IDNR) and the Illinois Capital Development Board announced last week.
Illinois Beach State Park in Lake County is constantly battered by Lake Michigan waves, making it a priority for preservation and mitigation efforts. Parts of the coastline have receded by as much as 100 feet in one year. Aerial photos and maps show how the shoreline, roads and dune ecosystems have been drastically altered.
The larger of the two projects is construction of a system to preserve 2.2 miles of Illinois Beach State Park shoreline. This is a $73 million project, which is believed to be the largest capital project in the history of the Illinois Department of Natural Resources (IDNR). Funding for the project was secured by the Capital Development Board (CDB) and made possible through the historic Rebuild Illinois capital plan. Construction is set to begin in spring 2023.
“It is a priority for IDNR and the State of Illinois to do everything we can to protect the precious public shoreline at Illinois Beach and the native species that live there before they both vanish forever,”IDNR Director Colleen Callahan said in a statement.
Rather than stopping erosion by building walls or high-profile coastal structures, the design seeks to guide and direct the movement of the sand instead of simply trying to prevent its movement. The approach uses creatively shaped and formulated islands and submerged reef structures, positioned out in the lake rather than built directly along the shore.
The unique solution is the result of more than a year of computer simulations and intense physical modeling to explore how Lake Michigan waves would behave passing around the structures and ultimately transform the shoreline. To test and verify design performance, consultants built a scale model in a giant hydraulic laboratory in the United Kingdom – larger than a soccer field – to replicate conditions along 11,000 feet of Lake Michigan shoreline.
More than 100 variations of possible shoreline solutions were tested until an effective solution was found. The lessons learned through this trailblazing effort set new standards and guidelines for how living shoreline design can manage highly erosive wave forces while remaining as natural as possible.
The completed project will use about 250,000 tons of rock fill and armor material, creating 22 submerged and low emergent stone breakwaters covering 12.2 acres of lakebed and renourishing the shoreline with nearly 430,000 cubic yards of sand.
“This approach reflects a broader change in the way shorelines are being protected around the globe,”Callahan said. “Our project explores new ground and sets new standards for what living shorelines can be and what we can achieve in the Great Lakes.”
The Illinois Capital Development Board (CDB) will oversee the project’s design and construction in accordance with the protocol for state-appropriated projects.
The second project involves the installation of stone “rubble ridges” in Lake Michigan off the southern end of the Illinois Beach State Park coastline. This pilot project is an example of an innovative design focused on development of lower impact and less expensive measures that can protect shoreline
Ridges are submerged in the water to preserve the view from the shoreline. They also create fish habitat by offering small, protected pore spaces within the structures – in effect, protecting habitat with habitat
“This project represents an important step toward the future of Great Lakes coastal resiliency,” said Ania Bayers, natural resources manager of the IDNR Coastal Management Program. “It’s also a testament to the importance of interagency collaboration, a reliance on good science, and innovative design to preserve the most basic and important qualities of the places Illinoisans love.”
Each year, winter wreaks havoc on Lake Michigan communities as waves and ice pummel the coast. More recently, storms combined with record-high lake levels have been especially damaging to the shoreline.
“From 2012 to 2020, a period coinciding with record-low to near record-high lake levels, the north unit of the park alone lost an estimated 670,570 cubic yards of sediment,” said Robin Mattheus, coastal geologist of the Illinois State Geological Survey. “To help put that into number into perspective, that’s enough to fill about 50,000 dump trucks.”
Construction of the rubble ridges will cost about $1.5 million.