Illinois geologists began a major project this week: They’re studying the patterns of sand deposits on Chicago’s beaches. Sand has disappeared from some shores, while building up in others, costing Chicago millions of dollars every year to redistribute the sand where people want to enjoy the beach recreationally, according to the Chicago Tribune. When high levels of erosion occur, it impacts tourism, housing developments close to the lake, power plants that rely on water circulation and other important structures for the city of Chicago.
According to Wheaton’s professor of geology James Clark, this problem is not a new one. “It’s a common problem in all coastal areas, because sand on a beach is continually moving, so the sand that’s on the beach this year is not the same that was there last year,” he explained. The process is called longshore drift, the movement and deposition of sand resulting from the constant movement of the water in the lake. In one sense, erosion on beaches and the movement of sand towards the south is a natural process. Clark recalled, “It was high in 1986, you had a lot of erosion. Since then, it’s been pretty low and now it’s going back up again. Erosion just happens.”
On the other hand, the issues of erosion that Chicago is experiencing are complicated by the presence of man-made structures. Because of the tourist attraction, losing sand in popular beach areas is inconvenient, leading to attempts to stop the natural process of erosion from happening. Clark highlighted the Beach State Park as an example of these attempts, saying, “They build things out onto the lake called groins … walls that go out into the lake and catch the sand and build it up there … they really do stop the sand from moving, but it means that further on down the sand doesn’t get there.” So the erosion happening in Chicago is is impacted by both natural processes and man-made structures.
In order to understand the entire process more thoroughly, the Illinois geological survey is utilizing large-scale “time-domain electromagnetics” with a helicopter at a high cost. Clark jokes, “A quarter of a million dollars seems like a lot of find out about sand!” He explained the basic structure of the device as an antenna and a transmitter that sends electric fields into the earth to determine the electrical resistivity of different layers of earth. “They’re making a kind of map,” he said.
The purpose, according to Clark is to “get an overall idea of the sand resource that’s available ” and “how thick it is where there is sand.”
Clark himself is building a small-scale version to use in Wheaton: “I think we can do it for about $300 and see how it works.” Since there is no perfect solution to the sand problem, geologists are primarily interested in understanding the causes and effects.