With dramatically variable Lake Michigan water levels, bigger storms and stronger winds, the effects of climate change have made managing sand along Chicago area beaches more challenging. And there’s no one-size-fits-all solution, according to Illinois-Indiana Sea Grant-funded research.
“A change in lake level can alter how sediment is routed along the shoreline and influence where it is trapped,” said C. Robin Mattheus, Illinois State Geological Survey (ISGS) coastal geologist. “Sand management is ongoing and understanding how and when sediment is mobilized is key to effective planning.”
As part of the Sea Grant study, Mattheus and a team of ISGS scientists monitored sand distribution along 18 beaches and in nearshore waters over the summers of 2022−23. This project was the first regional, high-resolution sand assessment along the Chicago shoreline.
“The massive data-collection effort of the past two years will help us understand shoreline dynamics more holistically. Knowing the offshore distribution of sand and how it moves around can help us understand what kind of future changes to beach environments are possible,” said Mattheus.
Left to right, Mitchell Barklage, geophysicist, and Liane Rosario, geospatial scientist—both with the Illinois State Geological Survey—gather ground penetrating radar data as they measure sand thickness on Chicago beaches. (Photo courtesy of Robin Mattheus)
The team used a variety of technologies and tools, for example, sonar, drones and underwater grabbers to sample sand, combining what they learned with historical data and previous studies that provided guidance on their approach to data collection, filled in information gaps and supplied context for their data.
The researchers found that knowing what’s happening with the sand that sits at the bottom of nearby waters is very important in understanding what changes take place on the beach. For example, all Chicago beaches became smaller when the lake level rose to its 2020 high. Some lost sand overall, however, some gained sand in their nearshore waters. Those beaches are recovering more quickly now that the lake level is near average.
When it comes to rising lake levels, solutions need to be site-specific. “Any given beach may have its own dynamic, influenced by the direction it is facing, the design of the surrounding infrastructure, and how much sand is being supplied from the updrift,” said Mattheus.
“In addition to the impact of lake levels, we have built peninsulas, groins, and jetties into the lake so sand can get caught up in a lot of different places,” he added. “We are just now starting to understand these regional versus site-specific influences on beach and lakebed dynamics.”
The sand along the Chicago shoreline drifts from north to south, with some getting hung up around structures along the way. Two popular beaches can help tell the story of sand distribution here—Montrose Beach near Uptown on the city’s north side, and Rainbow Beach, adjacent to the South Shore neighborhood.
Sand is plentiful along Montrose Beach because it has been trapped for nearly 100 years by a structure that was overbuilt. This pier extends into the lake by more than 650 yards, effectively trapping sand as it moves southbound.
The trapped sand feeds the beach, helps to grow dunes, and makes for shallow nearshore waters. It is also beneficial to the bird sanctuary on-site as well as the portion of this large beach that is set aside as habitat for piping plovers. In some recent years, these tiny shorebirds that are endangered in the Great Lakes have summered there, raising their young and becoming local celebrities.
Chicago’s south side beaches, including Rainbow Beach, tend to have less sand offshore that might move onto the beach than those on the north side. Rainbow Beach also has some specific features that reduce the potential for sand to come ashore.
“Rainbow Beach is much more enclosed by infrastructure than Montrose Beach,” said Mattheus. “The offshore geology is also different, so Rainbow Beach has evolved very differently than Montrose Beach, despite shared storm and lake-level histories. So, while the dune areas at both beaches were reduced in size during 2013−2020 lake-level rise, the dynamics of beach and dune recovery are very different, as a function of sand supply.”
The geology of its nearshore waters is just one reason Rainbow Beach on Chicago’s south side has less sand than Montrose Beach.
Mattheus and his team are compiling an extensive report that will provide beach-by-beach information for local managers to address sand issues at their particular site and have a better understanding of what to expect with changing lake levels. He envisions beach managers sharing information with others whose beaches behave in a similar fashion.
“A regional study such as ours provides the basis for grouping beaches into different types, based on shape, orientation, types of structures, and sand availability or supply. We hope our dataset can kick-start some discussions and entice future collaborative efforts to advance our understanding of coastal dynamics along the urban lakefront.”
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Illinois-Indiana Sea Grant is one of 34 Sea Grant programs supported by the National Oceanic and Atmospheric Administration in coastal and Great Lakes states that encourage the wise stewardship of our marine resources through research, education, outreach and technology transfer. In partnership with the University of Illinois Extension, and Purdue University Forestry and Natural Resources, Illinois-Indiana Sea Grant brings science together with communities for solutions that work.
