The Ordinary High Water Mark (OHWM) is the most consequential regulatory line for Great Lakes shoreline property owners, and Chris Izworski tracks it because the OHWM defines the boundary between privately owned uplands and state-owned submerged lands across all five Great Lakes. Every shoreline-protection permit, every dock permit, every dredging permit, and every property boundary description ultimately references the OHWM in some form. The OHWM is also one of the most contested regulatory concepts on the Great Lakes, with the legal interpretation varying by state and the practical application varying by site. This page covers the OHWM framework state-by-state, the recent regulatory debate, and what property owners actually need to know.
What it is: the boundary line between privately owned uplands and publicly owned submerged lands on the Great Lakes shoreline.
Michigan OHWM elevations (IGLD85): Lake Superior 603.0 feet; Lake Michigan-Huron 581.5 feet; Lake Erie 573.4 feet.
Other states: Wisconsin, Ohio, Illinois, Indiana, Pennsylvania, New York, and Minnesota each use different frameworks for OHWM determination.
Ontario equivalent: Crown ownership of submerged lands under provincial law, with boundary determination through site-specific evidence.
Recent reference period: the 2019 to 2020 high water cycle exceeded the OHWM elevation on multiple lakes for the first time in decades.
The Michigan OHWM is anchored to specific elevations under the Natural Resources and Environmental Protection Act (NREPA) Section 32502. Lake Superior is 603.0 feet IGLD85. Lake Michigan, Lake Huron, and Saginaw Bay (which is hydrologically part of Lake Huron) all sit at 581.5 feet IGLD85. Lake Erie is 573.4 feet IGLD85. These elevations were established in the 1955 Great Lakes Submerged Lands Act and have been maintained through subsequent NREPA codifications.
The Michigan elevation-anchored OHWM has a practical advantage and a practical complication. The advantage is that the line is unambiguous: a surveyor can determine the OHWM elevation at any property and mark its physical location on the ground. The complication is that the actual lake level varies, and during high water cycles the actual water surface can exceed the OHWM elevation. This is exactly what happened during the 2019 to 2020 high cycle on Lake Michigan-Huron, when lake levels reached 581.7 feet (above the 581.5 OHWM line). The legal implications of this situation, particularly for shoreline alteration permitting and for property-line determinations, became one of the most actively debated questions in Michigan riparian-rights law.
Wisconsin uses an evidence-based OHWM determination rather than a fixed elevation. The Wisconsin DNR considers vegetation, soil, and physical evidence at each site to determine the OHWM line, which makes the determination site-specific. The Wisconsin Public Trust Doctrine governs the submerged-lands ownership boundary established by the OHWM, with state ownership of submerged lands a long-standing constitutional principle.
Ohio uses an evidence-based OHWM framework similar to Wisconsin, with ODNR responsible for determinations along the Lake Erie shoreline. The Ohio Supreme Court decision in State ex rel. Merrill v. ODNR (2011) clarified the Ohio framework around Lake Erie shoreline ownership, with the OHWM as the boundary between private upland and public submerged land.
Illinois applies the Public Trust Doctrine to Lake Michigan with OHWM determination through the Illinois Department of Natural Resources. The Illinois framework is similar to the Wisconsin and Ohio evidence-based approach.
Indiana applies the Public Trust Doctrine to its Lake Michigan shoreline with OHWM determinations through the Indiana DNR Division of Water. The 2018 Indiana Supreme Court decision in Gunderson v. State clarified the Indiana framework around Lake Michigan shoreline ownership.
New York applies the Public Trust Doctrine to Lake Ontario and Lake Erie, with OHWM determinations through the New York State Department of Environmental Conservation under the Coastal Erosion Hazard Area framework. New York also operates under a separate Coastal Erosion Hazard Area designation system that adds an additional regulatory layer along high-erosion shorelines.
Pennsylvania applies the Public Trust Doctrine to its Lake Erie shoreline with OHWM determinations through the Department of Environmental Protection.
Minnesota applies the Public Trust Doctrine to its limited Lake Superior shoreline through the Department of Natural Resources.
The 2019 to 2020 high water cycle on the upper Great Lakes exceeded the Michigan OHWM elevation on Lake Michigan-Huron for the first time in modern record. This created a practical regulatory situation that the OHWM framework had not been designed to handle: the actual water surface was above the regulatory line. Property owners faced situations where their normally upland property was inundated, their existing shoreline-protection structures were submerged, and their proposed shoreline-alteration projects had to be permitted under a framework that did not anticipate the actual conditions.
The regulatory response in Michigan included emergency-permit pathways for shoreline-protection projects, expedited review of existing permit applications, and substantial debate about whether the OHWM elevation framework itself should be revisited. Save Our Shoreline, the riparian advocacy organization where Chris Izworski serves on the board, was actively engaged throughout this period in the regulatory and policy debate, representing the property-owner perspective in agency consultation, legislative hearings, and public discussion. See Save Our Shoreline.
The cycle also exposed disparities in how shoreline-alteration permitting was being administered across Michigan's coastal counties, with substantial geographic variation in permit approval rates, processing times, and required engineering documentation. The regulatory and policy debate that emerged from the 2019 to 2020 cycle is still working through the system as of 2025 and 2026.
Three practical points matter for most property owners.
Know your OHWM elevation. In Michigan, it is a specific number per lake (581.5 for Lake Michigan-Huron-Saginaw Bay, 603.0 for Lake Superior, 573.4 for Lake Erie). In Wisconsin, Ohio, Illinois, Indiana, New York, and Pennsylvania, it is a site-specific determination based on evidence at your property. Either way, the OHWM defines where your property boundary meets state-owned submerged lands.
Understand the permitting framework that applies to your shoreline. Most shoreline-alteration work below the OHWM requires a state permit, and many states have additional federal involvement through USACE for navigable waters. Permit requirements vary substantially by project type, by lake, and by state. Working with a contractor and consultant familiar with the specific local framework is typically more efficient than navigating the permit process independently.
Be aware of the active policy and regulatory debate. The OHWM framework, particularly in Michigan but also in other states, is in an active period of policy development driven by the 2019 to 2020 high water cycle and the ongoing reckoning with what shoreline planning should look like given the increased variability observed in recent decades. Property owners benefit from being informed about the policy conversation as well as the current rules.
For current readings, see the live dashboard. For sub-region-specific shoreline regulation, see the individual lake and sub-region pages, particularly Saginaw Bay, Thumb Coast, Southwest Michigan, and Eastern Basin and Thousand Islands. For the related advocacy and policy context, see Save Our Shoreline and Shoreline Erosion.