The Thumb coast of Michigan runs from Pointe Aux Barques at the tip of the Thumb south through Port Austin, Caseville, Harbor Beach, Lexington, and Port Sanilac to the lower Thumb, where the coast transitions into the broader southern Lake Huron shoreline. Chris Izworski tracks the Thumb coast as a distinct sub-region because it has one of the most consistently exposed open-lake shorelines on Lake Huron and one of the most thoroughly developed and politically organized property-owner communities on the Great Lakes. The Thumb is also home to several of the longest-running riparian advocacy efforts in Michigan, with Save Our Shoreline historically having strong membership and board presence along this coast.
Sub-region: Michigan Thumb coast, Lake Huron, Pointe Aux Barques to Lexington and Port Sanilac.
Major communities: Port Austin, Caseville, Harbor Beach, Lexington, Port Sanilac.
Lake datum: 577.50 feet IGLD85, the Lake Michigan-Huron datum.
Anchor years: 1986 cycle high, 2013 modern low, 2020 record monthly high at 581.70 feet.
Michigan OHWM: 581.5 feet IGLD85 under NREPA Section 32502.
State jurisdiction: Michigan EGLE Submerged Lands and Wetlands, NREPA Parts 325 and 303.
The basinwide Lake Huron level on the homepage is the right starting point. The Thumb coast faces east into the open Lake Huron with substantial fetch exposure from the east, northeast, and north. The dominant high-energy wind direction for shoreline impact is northeast, particularly during fall and early winter storm seasons, when sustained northeast wind drives waves directly onto the Thumb's east-facing shoreline with limited natural shelter. Sustained north and northeast wind also produces measurable set-up on the upper Thumb coast at Port Austin, Pointe Aux Barques, and Caseville.
The 2019 to 2020 high water cycle was the most consequential modern reference event for the Thumb. The combination of record lake levels and active fall storm seasons produced bluff retreat, beach narrowing, and shoreline-structure damage that prompted hundreds of emergency shoreline-protection permits along the coast. The Save Our Shoreline membership documentation from this period is one of the most complete property-owner records of any single high-water cycle in Great Lakes history.
The Pointe Aux Barques and Port Austin coast at the tip of the Thumb is the most exposed shoreline in the sub-region and has the most dramatic shoreline geology, with the limestone Turnip Rock formation and Port Austin Reef as distinctive offshore features. Property density is moderate to high, with a mix of year-round residential and vacation property.
The Caseville and outer Saginaw Bay coast on the north side of the Thumb is included in the Saginaw Bay sub-region for hydrologic purposes but has property-owner characteristics that overlap with the Thumb. The Caseville waterfront and the Sand Point and Sleeper State Park coast east of Caseville are part of the upper Thumb shoreline community.
The Harbor Beach and central Thumb coast from Port Hope south through Harbor Beach to White Rock and Forester runs along the most open-fetch east-facing shoreline in the sub-region. Harbor Beach has the largest federal harbor on the Thumb coast and substantial commercial and recreational marina infrastructure.
The lower Thumb coast from Lexington south through Port Sanilac and Lexington Heights transitions toward the broader southern Lake Huron shoreline at Port Huron. Property density is high along this section with a mix of year-round homes, vacation property, and small-town waterfront. The Burnside, Greenbush, and Croswell areas inland from this coast carry the agricultural and small-town character that defines much of the Thumb interior.
The Thumb is one of the most regulatorily active sub-regions on the Great Lakes for shoreline-protection permitting. Michigan EGLE NREPA Part 325 governs submerged lands and shoreline-alteration work, and the Thumb's combination of high property density, sustained shoreline-erosion exposure, and politically organized property-owner advocacy means that NREPA Section 32502 OHWM interpretation, individual permit decisions, and the broader policy questions around shoreline protection are all actively debated in this sub-region.
Save Our Shoreline, the riparian advocacy organization where Chris Izworski serves on the board, has substantial member presence on the Thumb coast. The organization's positions on OHWM interpretation, shoreline alteration permitting, and the regulatory framework around riparian rights reflect the experience of property owners along this coast through the 1986 high, the prolonged 1999 to 2013 low, and the 2019 to 2020 high cycle.
For a current reading, see the live dashboard. For broader Lake Huron context, see Lake Huron. For neighboring Lake Huron sub-regions, see Saginaw Bay, Sunrise Side, and Mackinac. For broader regulatory context, see Ordinary High Water Mark and Save Our Shoreline.