By Kyrmyzy Turebayeva
A new study documents a fivefold increase in shoreline armoring along Lake Michigan’s Eastern coast.
From 2014 to 2021, the length of engineered structures built to protect the shore from erosion grew by nearly five times.
Rising water levels and increased wave activity prompted many coastal communities to install seawalls, rock revetments and other protective structures, the study said.
“Armoring changes how sediment moves within the coastal system and how beaches recover after high lake levels, so we wanted to precisely document the scale of this process,” said Ethan Theuerkauf, the study’s lead author and a professor of geography, environment and spatial sciences at Michigan State University.
Researchers compared shoreline armoring data from 2014, collected by the National Oceanic and Atmospheric Administration, with high-resolution coastal imagery taken in 2021 after the period of peak water levels.
“The goal was not to classify different types of structures but to document the total length of shoreline that had been altered by human activity,” Theuerkauf said. “This provides a foundation for future work that can examine how armoring changes coastal systems.
The analysis revealed a substantial increase in the use of engineered structures along the shoreline.
“We had seen this anecdotally in the field and heard it from communities and agencies: During the period of rising water levels from 2014 to 2020, a large amount of shoreline armoring was installed,” Theuerkauf said.
The study found that the most substantial increase occurred along the southern third of the Lake Michigan coast, where some areas are now almost fully armored. In northern regions, the increase was smaller, but even there new armoring appeared on stretches that had previously remained natural.
“Because there was no updated documentation of how shoreline armoring changed during the period of rising lake levels, decision-makers had very little understanding of the scale of the issue,” Theuerkauf said. Our data can help develop strategies aimed at keeping the Lake Michigan coast as natural as possible while still providing protection where it is truly needed.
One notable example identified by researchers is Chikaming Township in Southwest Michigan’s Berrien County, where hard shoreline armoring is restricted. That area showed substantially lower levels of armoring than in neighboring municipalities.
“This example demonstrates that policies restricting armoring can have a real impact on the character of the shoreline,” said Theuerkauf.
The results of the study, published in the Journal of Great Lakes Research, have implications for shoreline management, Theuerkauf said.
“Homeowners can see how widespread and potentially impactful these practices have become. And government agencies can better understand how permitting decisions influence the functioning of Michigan’s coast,” he said.
Shoreline armoring is a common measure to protect property from erosion. It helps prevent damage to homes, roads and infrastructure. But widespread use of hard structures changes sediment movement along the coast and may affect beach recovery after periods of high water.
Shoreline armoring influences both the ability of beaches to recover after high lake levels and public access to the coast.
The extent of armoring was greater than the research team expected.
“There were places where the shoreline was almost completely armored. And nearly every city or township in Michigan had at least some amount of armoring,” Theuerkauf said.
Particular concern arises in Northern Michigan, where many natural, minimally developed shorelines remain and are important for tourism.
“These are the areas where coastal managers need to be especially careful when making future armoring decisions,” Theuerkauf said.
The researchers are now studying how beaches recover after periods of high water and how shoreline armoring affects this process.
“This work directly informs our research on coastal changes related to shoreline armoring and will help guide future coastal management policy,” Theuerkauf said.