Trying to stop beach erosion along shores of Lake Michigan

For the first time in 20 years, a little sand has returned to Langdon Park.

Once a large beach and boating area in this Chicago North Shore community, the park's waterfront has been reduced to bare bluff and rocky shore, severely eroded by the pounding waves of Lake Michigan.

That may be changing.

''This may not look like much,'' says park director Ray Van de Walle, pointing to the small buildup of sand that would barely fill a few sandboxes. But it could be significant. Some experts call the Wilmette project a step forward in the fight against shore erosion. Others are not so sure.

In the Great Lakes, eroding shorelines are a serious problem. The US Army Corps of Engineers conservatively estimates that the high-water period between 1972 and 1976 caused more than $150 million in damage (some of it from flooding). And the erosion continues to be a serious problem.

Two weeks ago, for example, a severe storm lopped off seven feet of shoreline at the Illinois Beach State Park. But the Wilmette park, some 25 miles to the south, lost nothing.

The product being used at Wilmette, called Seascape, is a flimsy, plastic fiber contraption. Looking more like a giant comb than an erosion stopper, it sits in six to 10 feet of water with flexible fronds floating upwards. The fronds slow incoming water, allowing the sand it carries to settle onto the Seascape base. Eventually, this forms a sandbar, which causes waves to break and lose some of their energy before they hit the shore.

Theoretically, sand could be collected between the bar and the shore - thus rebuilding the beach.

But Wilmette isn't basing any over-optimistic hopes on the 4-to-7-foot sandbar that has formed since the December installation, Mr. Van de Walle says.

''The theory is pretty sound, but the (Wilmette) experience is so short,'' says Chris Shafer, chief of the Great Lakes shoreline section for Michigan's natural resources department. ''We have to see how this thing works over a period of years - at both high- and low-water periods of the Great Lakes.''

Experts question the material's durability, especially in thick ice conditions common on the lakes during winter. And, they ask, could the product work along the more dynamic ocean shorelines?

Seascape has been installed in the Atlantic Ocean off a heavily eroded shoreline in Cape Hatteras, N.C. Although an estimated 300 feet of new beach has been added, experts say many factors could be at work.

The product may get a rigorous workout in Michigan, however. Mr. Shafer's department is considering test sites for the product. Storms tend to hit harder on that side of Lake Michigan than along the Illinois coast, he says.

The state beach in Zion, Ill., is also looking into Seascape, along with other offshore protection devices.

The use of Seascape reflects an ideological battle on how best to fight shore erosion.

For too long, coastal engineers have refused to get wet, says Edith M. McKee, a consulting geologist based in Winnetka, Ill. They have contented themselves with armoring the shoreline, regardless of the important offshore currents and terrain, she says.

One reason why conventional shoreline armoring has prevailed is that it is less expensive to build than offshore structures, says Larry Hiipakka, the area's chief of coastal engineering for the Corps of Engineers. And, in the ocean at least, offshore protection has generally not worked, says Robert Dolan, environmental sciences professor at the University of Virginia at Charlottesville.

Many erosion experts say the best solution is to let nature run its course. Protecting eroded shoreline in one area only increases erosion somewhere else. Only in certain cases, such as important resort areas, are erosion controls economically justified, they say.

In Wilmette, the Corps of Engineers proposed different solutions to the erosion that ranged from $400,000 to $1 million. The Seascape project cost the village about $3,000 (although the company bore much of the cost in order to try the product out).

Meanwhile, Ray Van de Walle eagerly watches Langdon Park to see if a sandbox of sand can once again become a beach.