MSU researchers determine rapid water level rise driving unprecedented habitat loss along Great Lakes coasts

August 17, 2021 - Diane Huhn

While many homeowners and beach enthusiasts may be rejoicing over the slightly lower lake levels and more expansive beaches in the Great Lakes region this summer than recent years, threats to area shorelines are far from over, according to researchers at Michigan State University. Erosion will continue to impact coastal areas according to recent research by Ethan Theuerkauf, an assistant professor with the Department of Geography, Environment, and Spatial Sciences at MSU, and Katherine N. Braun, a researcher with the Illinois State Geological Survey. Their findings published in the Journal of the Great Lakes Research indicate that increased fluctuations in lake levels due to climate change will likely drive sustained habitat loss.

Unlike ocean and estuarine coasts, where sea-level rise is the dominant driver of water-level fluctuations, water levels along large lake shorelines such as those of the Great Lakes fluctuate on the order of a meter approximately once a decade. It might seem fairly obvious that as water levels rise, shorelines can, and typically do, shift landward. And conversely, shorelines tend to shift lakeward during periods of low water. The historical and geological records for the Great Lakes region document numerous such swings over the last century.  It’s probably not surprising that analysis of the data indicates that the erosion rates of beaches, bluffs, and other coastal habitats can be significantly higher during periods of high water levels than the average long-term rates.

The study indicates that erosion rates during the most recent high-water period from 2014-2020 are not just a bit out of the norm- they appear to be unprecedented. At the primary study site in northeast Illinois near Chicago, the Theuerkauf team discovered erosion rates more than five times those measured during the previous high water events of the 1970s and 80s when water levels in Lake Michigan were actually higher than the recent levels.

Why the dramatic increase? “We often think that erosion rates are tied only to how high the levels rise, but our research indicates that erosion rates jumped significantly due to how quickly the lake levels rose as opposed to just how high they rose,” said Theuerkauf. Their analysis of the historical records indicated that lake levels rose twice as quickly as during previous periods. The team also determined a slight increase in the frequency of storm waves during this most recent period of lake level rise that also contributed to the increase in erosion rates.

According to Theuerkauf, the study suggests that these abrupt and high magnitude changes in lake level are highly effective at inducing erosion as they shift the coastal system quickly from one regime to another. “Given that climate change is likely to increase the variability in lake levels moving forward, we anticipate that we will see sustained habitat loss, especially without intervention.”  

Predicting just how much and how quickly water levels will change in the future does make it challenging to plan for future coastal conditions. However, results from the study indicate that ensuring that coastal elevation is at least 2 meters higher than projected water levels could help combat coastal habitat loss. “Our hope is that coastal managers can leverage this information to identify areas at risk of erosion and put in place targeted management strategies in response to specific events such as storms or seasonal water-level rises to reduce a site’s vulnerability to coastal erosion and habitat loss,” said Theuerkauf.  

A host of researchers in the College of Social Science are conducting cutting-edge research to better understand coastal change in the Great Lakes and beyond while simultaneously providing citizens and decision-makers with the timely information they need to adapt to these challenges. To learn more about this important Coastlines and People thematic research area, visit https://socialscience.msu.edu/research/thematic/coastlines/index.html.