Six years ago Lake Michigan was big news. Its waters stood at record high levels. In February 1987 a giant storm bashed the Illinois shoreline, flooding Lake Shore Drive and even slamming buildings on the North Side. News reports took on an apocalyptic ring. Then the lake levels dropped and the story evaporated.
“The last few years we’ve experienced dropping lake levels, and with that, much of the real threatening erosion has diminished,” said Ralph Volpe, parks superintendent with the Park District of Highland Park. “The truth is, however, that we have a continuing loss of sand. The beaches may look like they are bigger and wider because of the lower water levels, but the depletion of sand is continuing,” Volpe added.
A few geologists also maintain that the erosion problem has not gone away. “Sooner or later,” said Charlie Johnson, a coastal engineer with the U.S. Army Corps of Engineers, “lake levels will come up again and people will (face) the same problem.”
Johnson and a few others have the daunting task of trying to institute a large-scale program to control erosion by building new beaches, with public funds, at a time when the public perceives no crisis.
Their proposal is all the more ambitious because it would require a series of North Shore communities to agree on such divisive issues as tax dollars and public access to hitherto private beaches.
To understand the idea of building a beach, it is necessary to know what a beach is and how it works.
“Most people think of the beach as the part above the water,” said Charles Shabica, a geologist with Northeastern Illinois University. “But in terms of shore protection, what matters is sand on the beach and in the water near the shore.”
A vital part of a beach’s sand is actually offshore, unseen, in underwater sandbars that reduce the force of waves by causing them to break well offshore, where they do less beach damage.
In Lake Michigan, shoreline currents move north to south, carrying with them a load of sand and other sediment. This is known as littoral drift.
Beaches and offshore sandbars are constantly being ripped up by storms, moved south and rebuilt.
The North Shore is naturally prone to erosion; to protect lakefront bluffs and buildings set upon them, structures to capture sand and prevent it from moving farther “downstream” were built almost as soon as white settlement began-as early as the 1840s, Shabica said.
Breakwaters and groins (walls built at a right angle to the shore) were built to capture sand on their north sides and keep it from continuing south. The biggest was that at Waukegan Harbor, built by the federal government in the late 19th Century. With less sand flowing south, beaches shrank, and landowners were inclined to build their own breakwaters to capture sand and seawalls to protect bluffs.
Now, though, there is so little sand left on the North Shore that few large beaches remain, with the biggest Illinois Beach State Park. Shabica has been studying shore erosion in Illinois and Indiana since 1989 as part of a project funded by the U.S. Geological Survey.
By taking measurements of the lakebed one-third of a mile into the lake, from the Wisconsin border to Wilmette, Shabica concluded that there is a severe paucity of sand.
North of Waukegan Harbor, there may be a dozen feet of sand offshore; farther south there is so little the clay lakebed is exposed to wave action. “The lakebed is eroding more rapidly than we thought,” Shabica said. “The water’s getting deeper near shore, so storm waves are becoming higher, more powerful.”
Powerful storm waves not only strip away recreational beaches and threaten private property but also require municipalities and park districts to armor their lakefront facilities with ever stronger and more expensive fortifications.
The battle with the lake is a costly one. The North Shore Sanitary District, for example, runs a sewer line along Highland Park’s shore for slightly less than a mile. It has spent $500,000 in the last few years fortifying it to protect it from waves.
Lake Forest, meanwhile, has spent more than $9 million rebuilding, fortifying and enhancing recreational facilities at its relatively small public beach.
Shabica’s solution to this dilemma is to work with the lake, not against it. He proposes to “nourish” North Shore beaches by dumping millions of tons of coarse sand or gravel at a number of offshore locations. Over the course of several years, the currents would distribute the materials as they do naturally occurring ones, building beaches and offshore sandbars at one stroke.
The Illinois Beach State Park, at Zion, initiated beach protection measures more than 10 years ago, beginning with construction of splash aprons that protected buildings. The effort now focuses on rock deposits, placed along the park’s 7 1/2-mile shoreline to enhance the natural deposit of sand, and on a beach-nourishment program that works just as Shabica suggested.
“We transport the sand that has been deposited at the south end back up to the north end and then let it wash down,” said Bob Grosso, site supervisor at Illinois Beach State Park. The park also added 60,000 cubic yards of sand to the mix this year, to make up for a drop in the amount of sand being washed down from Wisconsin.
Many geologists agree that beach nourishment is a sensible and effective idea.
William Wood, director of the Great Lakes Coastal Research Laboratory at Purdue University, said, “Nourishment is the only way to get beaches back on the North Shore, since the whole shoreline there is sand-starved.”
Lake Forest, which completed its beach-restoration project four years ago, brought in enough sand to extend its 3,500-foot-long, manmade beach to a width of about 260 feet from the bluff to the water line. To protect those sand deposits from washing away, it also built a breakwater system tested on an engineering model in Ontario, Canada.
“The beach was completely gone,” said Paul Cadarian, Lake Forest’s facilities supervisor. “We did a referendum and the residents approved it. This is what they wanted.”
To obtain the Corps of Engineers’ permission for the project, Lake Forest also had to agree to deposit sand at the south end of its beach each year to compensate for the interruption of the littoral drift that its breakwaters may cause.
Because littoral drift will eventually disperse nourishment materials “downstream,” Shabica further suggests that the North Shore project should include a recycling provision. Every few years the sand or gravel that has traveled to Wilmette Harbor, which engineers consider a natural demarcation line, would be dredged up and shipped back to the north end, where it would be dumped in the lake again.
In theory, the rebuilt beach would last a long time. How long? It depends partly on the materials used.
Johnson wants to use gravel; Shabica thinks coarse sand will stay put almost as long and provide a better surface for beach towels and bare feet. Illiois Beach State Park is looking into using finely ground glass that has been buffed to remove jagged edges. “It emulates sand particles. In fact, it’s the same organic compound,” Grosso noted.
“Eventually the sand supply will run out,” Grosso said. The ground glass could cost less than sand and could be made from scrap glass, creating a new market for recycled glass. “It’s being tried in California, and we’re waiting to see how it works there first,” Grosso added.
Purdue University’s William Wood is monitoring five restoration projects on the lake’s east shore in Michigan.
From those projects, engineers have learned a great deal about how beach materials move and what types of sand and gravel are most appropriate for nourishment. In several cases, for example, fine sand quickly washed away; coarse sand and gravel are far more effective for beach building and erosion control.
None of the projects proposed for the North Shore has included funding mechanisms that would pay for large-scale, continuous dredging and recycling.
That gets into a much tougher area where even the most brilliant engineer can get lost: politics.
