Scenario-Planning Report

Acknowledgements

From the beginning of this work in February 2023 to the end of this work in January 2025, many people and organizations participated in the conversation and planning efforts to varying degrees. The organizations and individuals who participated in at least one engagement in the process include the following:

• 1854 Treaty Authority: Darren Vogt
• American Planning Association: Senna Catenacci; Joe DeAngelis; Jo Peña (former)
• Arrowhead Regional Development Commission: Justin Otsea (former)
• Association of State Floodplain Managers: Jason Hochschild; Beth Klusinske; Alan Luloff; Jenna Moran; Beth Zinecker, PhD (former); Eleanor Rappolee; Jeff Stone
• Coastal States Organization: Vidya Balasubramanyam; John Ryan-Henry
• City of Duluth: Jim Filby Williams; Adam Fulton (former); Mindy Granley; Tom Johnson; Kate Kubiak; Jenn Moses; Jason Mozol
• Fond du Lac Band of Lake Superior Chippewa: Alex Dufault; Wayne Dupuis; Arianna Northbird; Evan Schroeder; Richard Gitar
• Minnesota Department of Natural Resources: Rebecca Holmstrom; Clinton Little; Julie McDonnell; Bri Speldrich; Ceil Strauss; Mark White
• Minnesota Point 50 (MP50)/Park Point Community Club: Patricia Brownell Sterner; Dawn Buck; Dan Ross; Paul Treuer
• Minnesota Pollution Control Agency: Tom Estabrooks
• Minnesota Sea Grant: Madison Rodman
• National Oceanic and Atmospheric Administration: Brandon Krumwiede
• University of Minnesota: Nisogaabokwe Melonee Montano
• University of Minnesota-Duluth: John B. Swenson, PhD.
• University of Wisconsin-Platteville: Evan Larson
• Western Lake Superior Sanitary District: Sam Lobby (former)

Not all individuals listed here participated in the Action Plan development process. Their engagement may have happened earlier in the overall process.

Purpose of this Report

This report was created as part of the Strengthening Coastal Communities Resilience Challenge, which was led by the Association of State Floodplain Managers (ASFPM), American Planning Association (APA), Coastal States Organization (CSO), and the Great Lakes Sea Grant Network via Wisconsin Sea Grant (“Project Partners”) with funding provided by the National Fish and Wildlife Foundation. The Project Partners worked with a team from Duluth, Minnesota to support the community of Minnesota Point, which included representatives from Park Point Community Club and Minnesota Point 50 representing the residents of the Point, the City of Duluth, Minnesota’s Coastal Program, and regional experts from the University of Minnesota-Duluth (“Minnesota Point team”). The Project Partners and the Minnesota Point team collaborated from February 2023 to December 2024. This document is the final report related to the scenario planning and vulnerability assessments undertaken during this period. It is intended as a reference document for the participating team members to help them recall the process taken and conversations that led to the final results and maps that were developed.

Disclaimer

Executive Summary

The Strengthening Coastal Communities Resilience in the Great Lakes Region Challenge program, led by the Association of State Floodplain Managers (ASFPM), American Planning Association (APA), Coastal States Organization (CSO), and the Great Lakes Sea Grant Network via Wisconsin Sea Grant (“Project Partners”), is a two-year technical assistance program focused on helping coastal communities in the Great Lakes region better manage their dynamic coastlines and prepare for flood hazards. The goal of the challenge is to assess and model community flood vulnerability to identify strategies, ideally natural and nature based solutions, that can alleviate the specific coastal problems found on Minnesota Point — a community in Duluth, Minnesota. This work was made possible through the National Fish and Wildlife Foundation National Coastal Resilience Fund grant.

Minnesota Point is a seven mile-long freshwater sandbar off the southeastern shores of the City of Duluth that separates Lake Superior from the St. Louis Estuary and plays a crucial role in sheltering the Port of Duluth-Superior, Wisconsin, from the rough waters of Lake Superior. Minnesota Point or “Park Point” is home to a human population of 1,304 (2022) and to several rare and protected species, an old growth red and white pine forest, extensive sand beach, and a rare coastal dune ecosystem. These natural features and the built environment of Minnesota Point are at risk of damage due to coastal hazards, such as erosion and flooding.

Water levels on Lake Superior fluctuate on an annual cycle, rising in the spring and summer and declining in late fall. Seasonal, high intensity northeastern winds during autumn and early winter often create seiches and wave action which can inundate the Minnesota Point shoreline and cause severe flooding, especially when water levels are still high in early fall. The low elevation beaches and sandspits make the Point vulnerable to even minor fluctuations in Lake Superior’s water level, which can also cause occasional dramatic losses of beach sand. During high water periods, the beaches are vulnerable to being scoured away by wave action, and during low water periods, the sand is blown away by northeasterly winds. In the fall of 2019 alone, the point saw two coastal storms of similar size, in some cases waves on Lake Superior crested at up to 15 feet high, and access to and from Park Point was cut off, hampering emergency services. These two storm events had an estimated $30M in damages and repairs to shorelines. Large coastal storms on Lake Superior like these are the primary driver for flooding and erosion on Minnesota Point. The variability in water levels and storminess along the Great Lakes coastline present a unique challenge to coastal communities, creating a wide range of possible scenarios and hazards that communities must consider as a part of their current and future coastal management plans.

Scenario planning provides a way to establish and compare plausible narratives for the future, accounting especially for the uncertainties inherent in dynamic natural systems. Unlike other techniques such as forecasting, however, scenario planning does not try to predict the future. Rather, the narratives, which are based on valid economic, social, and environmental data about the present and projected future conditions, simulate uncertain aspects of the future by considering multiple variables and perspectives. They then articulate an array of reasonable potential futures from which decisions regarding uncertainties can be framed and planned for by the community.

The Minnesota Point team, through the Great Lakes Coastal Resilience Challenge, has worked with the Project Partners to develop a set of three climate future scenarios (Lucky, Expected, and Perfect Storm) based on scientifically derived data, including FEMA Flood Maps and NOAA Lake Level Viewer data, and mapped across the community’s current buildout to highlight how various management decisions and adaptation strategies might improve or impair the community’s resilience in the future. The Lucky Climate Future is the best case scenario and represents low lake levels with some influence from an extratropical storm. The Expected Climate Future represents average lake levels with some influence from an extratropical storm. The Perfect Storm Climate Future is the worst case scenario and represents high lake levels with some influence from an extratropical storm. These three climate future scenarios were mapped and verified by the community and subject matter experts.

Using FEMA’s Hazus Flood Assessment Structure Tool (FAST), a vulnerability assessment was conducted for each of the three climate future scenarios. Flood depths derived from the NOAA Lake Level Viewer and structural information collected from the St. Louis County tax assessor’s database were used as data inputs for the vulnerability assessment. Using depth-damage functions, FAST outputs provide a breakdown of possible flood losses as a result of extended periods of inundation of certain depths in terms of US dollars for the three climate future scenarios, giving the community a better idea of the number of structures at risk and overall vulnerability to flood hazards.

Fortunately, around 2010, the city enacted a building standard minimum of “equal to the 100-year flood (1 percent annual chance flood) elevation plus stage increase due to establishing floodway plus two feet of freeboard.” Per FEMA, freeboard is a “factor of safety usually expressed in feet above a flood level for purposes of floodplain management.” On Minnesota Point, the current building minimum standard given FEMA’s defined Base Flood Elevations (i.e. 100-year flood elevation) for the area is 607 ft (IGLD 1985) or greater, depending on where you reside on the Point. This requirement means that newly developed properties and some remodeled properties must have a first floor elevation of at least 607 ft and/or two feet of freeboard above the base flood elevation, and cannot have a basement. However, many older builds predate this building code and have first floor elevations or basements below the 607 foot threshold, making them more vulnerable to flood hazards.

The Great Lakes Coastal Resilience Challenge

There is little technical assistance and guidance for local governments currently available for implementing Great Lakes coastline management best practices during high and low water level periods. In support of this need, the Association of State Floodplain Managers (ASFPM), American Planning Association (APA), Coastal States Organization (CSO), and the Great Lakes Sea Grant Network via Wisconsin Sea Grant are working together with Great Lakes coastal communities to increase community and local government knowledge on coastal hazards and better manage their dynamic coastlines and prepare for flood hazards through the undertaking of existing plan and policy review and scenario planning and vulnerability assessment to improve the development of future local master plans, regulations, and infrastructure policies and projects. This effort is called the Great Lakes Coastal Resilience Challenge and is funded by the National Fish and Wildlife Foundation (NFWF).

Cohorts from four Great Lakes communities participated in the Great Lakes Coastal Resilience Challenge from 2022–2024. Among these four participating communities was the community of Minnesota Point, a neighborhood bound by water as a part of a baymouth bar located in Duluth, Minnesota bound by water (Figure 1).

Minnesota Point, Duluth, Minnesota

Minnesota Point, also known as “Park Point,” is part of the largest freshwater sandbar in the world. The Point separates Lake Superior from the St. Louis River estuary, and shelters the Port of Duluth-Superior from coastal storms. As the highest tonnage port on the Great Lakes, this international port is a major driver of the regional economy. The coastal sand dunes and many of the associated plant communities that have developed over time on this baymouth bar are found nowhere else in Minnesota. They support plants and animals that are well-adapted to the special conditions, including several species that are state protected. The native plant communities (Sand Beach, Beachgrass Dune, Juniper Dune Shrubland, and Red Pine-White Pine Woodland) are all considered rare and have been assigned the highest statewide conservation status rank of S1, critically imperiled, due to their unique attributes and limited distribution in the state. Minnesota Point has a significant use and importance by indigenous people and current cultural significance. For nearly 14,000 years, Native people have lived at Waiekwakitchigami, the end of Lake Superior, which in French is called “Fond du Lac.” At the foot of the point of land called Neyaashi, now Minnesota Point, a short portage allowed Native people to pass from the shore of the great lake, Gichigami, into the bountiful estuary of Gichigami-ziibi, the outlet of the St. Louis River. Today, standing in the midst of the bustle of Canal Park watching ships pass, many visitors to Duluth are unaware of the Native heritage of that location and the little portage, or Onigamiinsing, around which the city grew (Fond du Lac Band of Lake Superior – Duluth Stories).

Coastal Hazards on Minnesota Point

Much of the Lake Superior shoreline consists of bedrock bluffs that are highly resistant to erosion. These coastal landforms are found on the western side of the lake, from the US-Canada border to an area near Duluth, Minnesota, and in eastern Wisconsin and the south-central shoreline of the Upper Peninsula of Michigan. The far western corner of the lake, near Duluth, Minnesota, consists of highly erodible red clay bluffs along the north shore. Along the southwestern shore of Duluth, Minnesota, and Superior, Wisconsin, is a highly erodible sand bar, Minnesota Point, and a bay-mouth sandbar, Wisconsin Point, both of which extend across the mouth of the St. Louis River, providing a coastal barrier for the St. Louis River Estuary, the Port of Duluth, and Superior, Wisconsin, from the rough waters of Lake Superior (Figure 2).

Much of the Point, from 43rd Street to its east end (including the SNA), is protected under the Coastal Barrier Resource Act (CBRA). A coastal barrier protects the waters and mainland that lies behind it against the impacts of severe coastal storms and erosion. The Minnesota Point Coastal Barrier Resource System Unit (CBRS) unit protects the St. Louis River Estuary, the Port of Duluth-Superior, and Superior, Wisconsin from the rough waters of Lake Superior. Having a CBRS unit designation withdraws the availability of federal disaster recovery funding and financial assistance from the designated coastal areas, discouraging development and encouraging the movement of people and property out of harm’s way.

Like many other sandy barrier islands around the world, fluctuating water levels and battering storm waves are flooding and eroding Minnesota Point from all angles. Lighthouse piers, controlled by the United States of Army Corps of Engineers (USACE), have stopped sediments from replenishing Minnesota Point and the lake bottom is slowly but unevenly springing back from the weight of the glacier that formed it, a phenomenon known as glacial rebound, tipping even more water toward Duluth. Glacial rebound amongst the cyclical variability in lake levels are represented by historical lake level data collected in Duluth’s harbor from 1860 to 2021 (Figure 3). The dashed line in Figure 3 shows the expected rise in lake level from geodynamical models of post-glacial rebound (Cramer and Wisotzsky, 2021). The red line is a simple linear fit to the observed lake-level time series. Additionally, these lake level data reveal a short-term cycle of low and high water level periods that tend to last around 10-13 years and can differ by 1-2 feet (Watras et al., 2014). Climate scientists predict that these high and low water level periods will become shorter and the difference in lake levels will become more extreme, meaning there will be higher highs and lower lows in lake levels over a time period less than decade long (Wilcox et al., 2007). If you take a magnifying glass to Figure 3, you can see evidence of a seiche as well, which is a standing wave in which the largest vertical oscillations are at each end of a body of water. For Duluth, the seiche has an 8-hour wave period, causing a 1-foot fluctuation in lake levels.

In addition to glacial rebound, projections show that ice cover duration on Lake Superior will decrease by one to two months by the end of the century as the climate continues to warm (WICCI, 2021).

Greater wave energy reaching the coast combined with high water levels associated with glacial rebound and seasonal precipitation will lead to increased erosion and flooding of the shoreline. During times of higher water levels, these large waves will be able to reach further inland and cause greater wave-associated damage and flooding. In the past fifty years, Duluth has experienced a number of significant flood events. The National Weather Service (NWS) provides summaries of these recent flood events occurring on the following dates in Figure 4a and 4b:

Notice that most of these flood events occur during the fall to early winter months when lake levels are higher due to seasonal increases in precipitation. In the fall, Duluth tends to experience storm events with seasonally high winds that, combined with high water levels, can cause significant damage to vulnerable areas. Based on the lake level and storm conditions, inundation can last for hours or days and change in severity over that time frame.

Related to flooding, erosion on Minnesota Point in Park Point has been a major concern since at least 1970, when studies of it began. The low elevation beaches on the lakeside make Minnesota Point vulnerable to even minor fluctuations in Lake Superior’s water level. During high water periods, the beaches are vulnerable to being scoured away by wave action, and during low water periods, the sand is blown away by northeasterly winds. Residents are concerned about these occasional dramatic losses of beach sand. The sediment source for the Point likely is restricted by the federal structures (e.g., shipping canal piers), under the control of the United States Army Corps of Engineers, located on either side of the Point. With no sediment source, the only way to slow erosion and maintain the beach is to periodically dredge the harbor and dump the spoils onto the lakeside of Minnesota Point.

In contrast, on the harborside, much of the shoreline is armored to protect the shoreline from erosion caused by wave action from severe storms or freighters. A simplified cross-section of Minnesota Point using graphics pulled from Federal Emergency Management Agency’s (FEMA) mapping documentation was created to demonstrate coastal hazards and how they manifest differently on either side of the point (Figure 5). Minnesota Point is significantly eroding from both sides and to address this issue, Point Park residents and the city of Duluth have resorted to using beach replenishment and hard armoring as solutions. However, these are both short-term solutions and have many ramifications that will only make matters worse in the long-term.

Minnesota Point’s future is important to the more than 300 residential structures, hotels and other businesses that call it home, as well as the bustling shipping industry that relies on the safety it provides for the Port of Duluth-Superior (Louwagie, 2019). The City has developed a Small Area Plan for Park Point (2016) to augment their Comprehensive Land Use Plan. One of the goals of this plan is to determine the carrying capacity of the land for future commercial and residential development. The carrying capacity of land is the number of people and level of human activity that can be sustained without degrading the land. Outside of the realm of government, the Park Point Community Club has initiated a grassroots effort to develop a long-term resiliency plan. This plan – MP50 – includes goals, strategies, and actions for mitigating and adapting to flood and erosion damage on the Point, but more assistance has been identified as needed, leading to the formation of the Minnesota Point team and its participation in the Strengthening Coastal Communities Resilience in the Great Lakes Challenge.

Our Approach

To address these coastal issues on Minnesota Point, the Project Partners worked collaboratively with the Minnesota Point team to come up with long-term adaptation strategies to enhance the resilience of Minnesota Point to coastal hazards, using the following process:

1. Undertaking a self-assessment and planning analysis to assess gaps in the city’s resilience plans and policies (methods derived from Wisconsin Sea Grant and Texas A&M University in collaboration with the University of North Carolina at Chapel Hill, respectively);
2. Developing a scenario plan and vulnerability assessment for Minnesota Point (methods derived from Norton et al., 2019 and APA);
3. Developing a Coastal Resilience Action Plan for Minnesota Point, and
4. Hosting two regional training workshops and two site visits to exchange valuable information on issues on the ground and to ground truth data.

The overall objectives of this approach were to help Minnesota Point residents and the city of Duluth to:

1. Assess community flood vulnerability,
2. Develop plans and policies that emphasize natural and nature-based solutions,
3. Build a community of practice with other local, state, academic, and NGO partners,
4. Identify funding sources that meet their needs, and
5. Ultimately enhance coastal resilience or the community’s ability to respond to coastal hazards.

As previously mentioned, this report focuses on the development of a scenario plan and vulnerability assessment for Minnesota Point. It is intended as a reference document for the participating team members to help them recall the process taken and conversations that led to the final results and maps that were developed.

The Scenario Planning Process

Uncertainty is the number one barrier of climate planning. To plan for uncertainty, a government must have the institutional capacity and political will to model various scenarios and policies. Many coastal municipalities simply do not have the resources or know where to start when planning for the potential effects of future climate-driven coastal hazards on their growing communities.

The scenario planning process described here is a decision-centered scenario-based planning method that was developed by Richard K. Norton, Stephen Buckman, Guy A. Meadows, and Zachary Rable and tested in the city of Grand Haven and Grand Haven Township, Michigan. This process accounts for uncertainty, while also using off-the-shelf data sources and basic techniques that any municipality, big or small, should theoretically be able to harness. By combining climate futures with management options to create a number of scenarios with varying outcomes, this method simplifies the complexity around improving coastal community resilience, so that community leaders and planners can make informed decisions. This process is broken down into three steps, which are visualized in Figure 6:

1. Map Climate Futures
2. Define Management Options
3. Combine and Create Nine Scenarios

Step 0: Gathering the Data

To begin the scenario planning process for Minnesota Point, the Project Partners compiled and mapped foundational data layers including elevation, regulatory floodplain maps, land use, critical infrastructure, and building footprints for Minnesota Point. A more extensive list of the data layers used in this process can be found in Appendix I. These data layers were mapped and shared with stakeholders using ArcGIS Pro Software and ASFPM’s Flood Science Center Esri Community organizational account.

Step 1: Mapping Climate Futures

Norton et al call for the development of three potential climate futures. It is important to note that these climate futures are not strict predictions, but are possibilities that provide a spectrum of simplified outcomes. Flooding is a dynamic hazard that can last for hours or days depending on lake level and storm severity. Therefore, each climate future represents a combination of still water level and storm severity to simulate Minnesota Point’s vulnerability to coastal flood hazards. To simplify this, the method has users assume storm severity is increasing with each climate future – Lucky being the “best” case scenario and Perfect Storm being the “worst” case scenario as described in Figure 7.

In order to map these climate futures, the Project Partners and Minnesota Point team defined what water levels and storm severity meant in the context of Minnesota Point’s geologic, climatologic, and hydrologic history in consultation with subject matter experts from the University of Minnesota-Duluth, City Public Works officials, long-standing residents, and other vested parties. This consultation happened across multiple virtual meetings and two in-person site visits. Discussions consisted of people with diverse backgrounds and interests having tough conversations around which variables to consider in delineating and mapping potential climate futures. It was helpful to remind the team that these climate futures are not meant to be predictions, but possibilities, which seemed to help the group find compromise and move conversations forward. The team went through a couple iterations before agreeing on how ultimately to determine water levels and storm severity for Minnesota Point given the available data.

Version 1: Lake Levels and Wave-Runup Data

On Minnesota Point, high lake levels can contribute to flooding that causes damage over a longer period of time (typically greater than an hour) and can be influenced by inputs such as seasonal precipitation, and storm surge. Additionally, short-period, wind-generated storm waves dissipate their energy by interacting with the shallow lake bottom, causing them to steepen, break, and run-up onto the shore and be highly transformed by local topography (Cramer and Wisotzsky, 2021). With this in mind, the first iteration of Minnesota Point’s climate futures looked to leverage historic lake level data for water levels and wave-runup data for storm severity. This data would then be combined to create a stillwater elevation for each climate future that could then be mapped.

This iteration was ultimately scrapped. It was determined that the short duration of wave-runup and the fact that wave-runup data is not widely available due to its complexity and high dependence on local topography made this methodology not ideal for the purposes of this effort. The Project Partners would need to amend the Norton et al. methodology slightly to conform to the needs of Minnesota Point.

It also was noted that high velocity zones or VE zones containing wave-runup information were decidedly not mapped for Minnesota Point in FEMA’s 2024 update to Duluth’s regulatory floodplain maps. The FEMA maps did not include wave runup because the models determined that the wave height was no greater than identified coastal features (Figure 8a).

Version 2: Lake Levels and Inundation

For iteration two, the team decided to exclude short-period, wind-generated waves and only consider storm-specific lake-level fluctuations of more than one-hour duration – or what is considered inundation – such as storm surge, and seiche. It also decided the maximum flood elevation for each climate future would be a sum of five components, as listed here.

1. Crustal rebound. Approximately 10,000 years ago, the glacier that filled the depression now known as Lake Superior melted, thus removing an immense load from the Earth’s crust. Much like the filling in of a ‘sitzmark’ on a memory-foam mattress, the crust and underlying mantle have been rebounding ever since. Because the glacier was thicker in the northeastern region of the lake basin, the crust is rebounding faster there compared to the Duluth area, where the glacier was less thick. The crust beneath the entire lake basin is rebounding, but the gradient between southwest (Duluth) and northeast (Michipicoten Island) has the effect of ’tilting’ the basin. The St Marys River, which forms Lake Superior’s outlet and sets its overall level, is located roughly midway along this rebound gradient. Hence, in the Duluth area, the lake level is rising compared to the surrounding bedrock landscape. (Note: This lake level rise has flooded the St. Louis River to form the estuary and the harbor.) This phenomenon has been understood for more than a century. The latest study (Cramer and Wisotzsky, 2021) constrains the rate of lake-level rise in the Duluth area to be about 3 mm/yr. This steady lake-level rise will persist for thousands of years to come; in the next 50 years, the community can expect about six inches of rebound-driven lake-level rise on Minnesota Point.
2. Decadal-scale lake level changes. Lake Superior’s level fluctuates by 1–2 feet on longer, roughly-decadal timescales (Watras et al., 2014). The driver for these fluctuations is not well understood but likely is related to larger-scale variations in atmospheric pressure.

3. Seasonal Lake Level Changes. In addition to decadal lake level changes, lake levels in Lake Superior typically fluctuate by 1-2 feet seasonally, with high water periods typically being in August and September and low water periods being in March and April. These fluctuations are driven by seasonal changes. From late spring through late summer, as the lake slowly warms, rainfall and associated runoff exceeds evaporation and the lake level rises; in contrast, from late fall into winter, precipitation rates decrease overall and evaporation decreases due to extensive ice cover. However, projections show that ice cover duration on Lake Superior will decrease by one to two months by the end of the century as the climate continues to warm (WICCI, 2021).
4. Storm surge. Minnesota Point is affected by large coastal storms known as extratropical cyclones. These storms form in the southwestern US and then move to the northeast. As the cyclone approaches the Duluth area, strong winds from the east or northeast ‘pile up’ water on Minnesota Point, leading to a six- to 12-hour period of increased lake level, which is known as ‘storm surge’ (Figure 8b). The largest storms can generate about 30 cm (1 foot) of lake-level rise.
5. Seiche. The Great Lakes are known for their strong seiche, which is a large-scale ‘sloshing’ of the water within a lake basin akin to the oceanic tide but driven by atmospheric pressure differences and not by Moon-Earth-Sun interactions. It is often called “the bathtub effect,” as one might notice a similar phenomenon of their bathtub water oscillating when they exit the tub. In Lake Superior, the most important seiche lasts about eight hours. Because of the geometry of the western Lake Superior basin, seiche can increase lake levels by as much as 25 cm (9.8 inches) in the Duluth area.

The logic behind defining the second iteration of Minnesota Point climate futures started with rebound and decadal-scale lake level fluctuations. The data suggests that in 50 years, glacial rebound will have raised lake levels by about six inches. Historical (1870-present) lake-level data in Duluth shows that lake levels in Lake Superior have high and low periods differing by 1-2 feet and lasting for 10-13 years (Watras et al., 2014) (Figure 3). If no other variables were considered, the climate futures would be defined as such:

• Lucky: Lake Superior is in the middle of a low lake level period (−12 inches) and has risen due to glacial rebound (+6 inches). Therefore, in this climate future the lake level would be about 6 inches lower than today’s average of 601.7 ft = 601.2 ft
• Expected: Lake Superior is at its average level of 601.7 ft and has risen by 6 inches due to glacial rebound = 602.2 ft.
• Perfect Storm: Lake Superior is in the middle of a high lake level period (+12 inches) and has risen due to glacial rebound (+6 inches). Therefore, in this climate future the lake levels would be 18 inches higher than today’s average of 601.7 = 603.2 ft.

Once these baselines were established, the team determined how to add in the remaining three variables: seasonal lake level changes, storm surge, and seiche. Together these three variables create a hypothetical, yet plausible extratropical cyclone that could occur in the late-summer or fall when there is typically more precipitation (inflow) than evaporation (outflow) occurring in the region. This hypothetical extratropical cyclone could increase water levels by 2.6 feet.

An additional 2.8 feet would result in the following stillwater elevations for each storm-related climate future scenario. The final lake level totals for each storm-related climate future can be found in Figure 9 and a map of the corresponding climate future hazard areas in Figure 10.

So, the scenarios would be defined as:

• Lucky: 604 ± 0.1 ft
• Expected: 605 ± 0.1 ft
• Perfect Storm: 606 ± 0.1 ft

The above numbers (Figure 9) are informed by lake level data collected on the harborside of Minnesota Point; the source for this data can be found in Appendix I, Lake Level Data, NOAA Tides & Currents for Duluth, MN (Station ID: 9099064). Modeling suggests these data should be nearly identical to the levels on the lakeside of Minnesota Point. The seiche cycle is phase lagged a bit in the harbor, as a result of the signal propagating through the channels, but the magnitude is preserved. It is possible that storm surge is a little bit higher on the lake side, but there is no easy way of constraining the difference.

These numbers also correspond to the FEMA Flood Insurance Study and subsequent flood maps created in 2024, where the models determined base flood elevations (BFEs) for Minnesota Point, which range from 604 to 606 feet and are included in the metadata of the preliminary floodplain maps shown in Figure 8a.

City of Duluth Regulatory Flood Protection Elevation

The City of Duluth’s building elevation requirement is defined in Article 6. Definitions. of its Unified Development Chapter (UDC) under the term “Regulatory Flood Protection Elevation.” The city defines its regulatory flood protection elevation (RFPE) as “equal to the 100-year flood (1 percent annual chance flood) elevation plus stage increase due to establishing floodway plus two feet of freeboard.” This means that all structures located within the 100-year floodplain must be elevated so that the walking surface of the lowest floor is at the RFPE or higher.

To break that down:

• The 1 percent annual chance flood elevation is also known as the base flood elevation (BFE); it is listed on a community’s FEMA Digital Flood Insurance Rate Map as, for example, (EL 606).
• Stage increase refers to how the new or improved structure will impact flood waters. Development in the floodway will cause an increase in the flood stage unless properly mitigated as the floodway can only hold so much water. NOAA defines the flood stage as the point when “a rise in water surface level begins to create a hazard to lives, property, or commerce.” Duluth requires that the development of any structure not cause the flood stage for any given location to rise more than 0.5 feet.
• Lastly, freeboard is a building standard requiring a structure’s lowest floor to be built a certain number of feet above the BFE. The lowest floor is the lowest enclosed area in the structure including a basement or crawl space.

This RFPE requirement applies to all non-commercial structures built on Minnesota Point; commercial structure requirements vary slightly.

Additionally, it is worth noting that no new builds on Minnesota Point can have basements and the lowest finished floor and mechanicals need to be above 607 ft (or greater), depending on where you reside on the Point and what FEMA’s defined Base Flood Elevation (or 100-year flood elevation) is for that given location. The data from 2024 FEMA Flood Insurance Study and subsequent flood maps and this effort further support this standard. When the building standard is mapped alongside the climate futures, as seen in Figure 10, you can see how it effectively works to protect new development in the community from flood risk, as the standard of 607 ft is higher than the perfect storm climate future at 606 ± 0.1 ft.

As shown here, structures built prior to the building standards enactment may be at higher flood risk as the previous building standards were less stringent. However, there are actions homeowners of properties built below the base flood elevation can take to reduce their flood risk. See Reflections and Recommendations.

Step 2: Defining Management Options

The next step in the scenario planning process is to frame out an array of options the community might employ to manage the current and future use of Minnesota Point. This allows jurisdictions to assess their current and potential risks to coastal hazards under different climate futures, as well as visualize how different development options intersect with uncertainties about climate. Similar to mapping three potential climate futures in step one, this step under the Norton et al. method involves defining three potential land management options, which include: Current Conditions; Full Buildout under Current Zoning; and Full Buildout with Best Management Practices Zoning (Figure 12).

Talking about future development on Minnesota Point was a topic of much debate for a group of stakeholders with competing interests. Similar to the discussions around climate futures, there were in-depth conversations before compromise on management options were reached.

To start, the Project Partners and Minnesota Point team discussed the following questions:

1. What does the community of Minnesota Point currently have in terms of structures and infrastructure?
2. What assets (these could be places, people, experiences) does the community of Minnesota Point want to still see on Minnesota Point in 100 years?
3. What does Minnesota Point’s current zoning ordinance allow for in terms of future development?
4. What kinds of Best Management Practices (BMPs) might the community of Minnesota Point wish to implement that could restrict exposing future development to high risk floods? Some examples might include setbacks, open space preservation, wetland restoration, etc.

Additional details on the discussions around these questions can be found in the Action Plan, which outlines a vision for the future of Minnesota Point and contains a list of actions to work towards implementing.

Existing Assets of Importance

The Minnesota Point team identified six broad assets that were important to the community and broke them further down into lists (Figure 13).

Figure 13. A list of assets identified by the community broken down into six groups: Environmental Health and Biodiversity, Parks and Recreational Opportunities, Culturally Significant Areas, Public Infrastructure, Residential Structures, and Commercial Structures.

Assets to Preserve

When asked which of these assets they most want to see preserved 100 years from now, the group agreed it depends on who you ask. Residents would want to see homes still on Minnesota Point. Environmentalists would want to see biodiversity preserved. After discussion, the following main priorities were agreed upon:

• Natural resource priority: preservation of the Minnesota Point Pine Forest Scientific & Natural Area, dunes, and estuary
• Recreational priority: preservation of the beaches on Park Point
• Economic priority: preservation of Minnesota Point as a coastal barrier to protect the Port of Duluth-Superior

Of note, with regard to the recreational priority, during its last comprehensive plan update, the City of Duluth surveyed the community. They included a question asking what residents like about Duluth. Many of the write-in answers included responses about Minnesota Point, showing that the whole community values it as an overall asset to and huge part of the identity of the larger Duluth community as the largest sandbar in the world. Residents in particular called out their love of hanging out at the beach and swimming in Lake Superior.

Best Management Practices

The City of Duluth’s current codes are defined in the Unified Development Chapter (UDC) of the city’s legislative code. The UDC guides land use and development in the City. The city has adopted model floodplain and shoreland ordinances and regulations as recommended by FEMA and Minnesota Department of Natural Resources (DNR); these are part of the Natural Resources Overlay section of the UDC. Examples of current regulations within the code include a 50 foot setback from Ordinary High Water Level or highest known water level for all residential structures, a 2-foot freeboard requirement (as previously described in the “City of Duluth Regulatory Flood Protection Elevation” section), a requirement to not to remove natural vegetation without a permit or variance, and 4,000 minimum lot area per single family dwelling. Discussion was had around access points to recreational areas and development potential on undeveloped land or the combination of multiple small plots.

As the city typically follows recommendations from the state or federal governments, these policies are not likely to change without strong data to support the need for change. One of the identified actions in the action plan that was created to accompany this assessment included research on what if any areas might benefit from development limitations due to coastal hazards and potential programs and regulations that are best practices to limit this development. Overlaying any changes in existing code is a desire to maintain the community’s character and preserve its current mixed-use development. With this in mind, the team agreed it would be best to continue the process by not mapping the two full buildout management options and instead map only the current conditions and complete a vulnerability assessment of the current conditions under the three climate futures. With these adjustments, the updated scenario planning framework is shown in Figure 14.

Beyond the discussion around the UDC and potential changes to it, the best management practices discussion focused on dune restoration and reconstruction, dune protection, preservation of parks and open space, and risk communication to the residents of Park Point on coastal hazards. Parks and open space on the Point identified for further planning for their preservation and protection included the Pontliana Woods, 13th Street Beach, Southworth Marsh, Minnesota Point Scientific and Natural Area, Park Point Community Recreation Area, and the entire Minnesota Point lakefront. An action plan was created at the close of the Challenge. Activities related to these BMPs were included.

Step 3: Conducting a Vulnerability Assessment

In this third and final step, the Project Partners conducted a vulnerability assessment for the three climate futures under the current conditions on Minnesota Point. The purpose of a vulnerability assessment is to provide the community with valuable information about areas or populations that are most vulnerable to coastal hazards, climate change, and related impacts. Vulnerability includes the exposure of the natural and built landscape to different hazards, as well as an accounting of how sensitive a community or segments of a community are to the hazards identified. When thinking of exposure, think of a building’s proximity to the shoreline. For sensitivity, think of the characteristics of the building that might impact the building’s ability to hold up during a flood, such as age or foundation type. Together, exposure and sensitivity equal vulnerability.

For the purposes of this study, the Project Partners measured vulnerability in the form of potential damage costs to properties using the Hazus Flood Assessment Structure Tool (FAST). FAST calculates building-level flood impacts with user-provided building and flood depth data. FAST uses the Hazus Flood model methodology to assign depth damage functions to buildings according to their occupancy type, first floor elevation, foundation type, and number of stories. Flood depth is then extracted at every building and used as a depth damage function parameter to calculate flood losses in dollars. A diagram depicting this process is found in Figure 15.

Exposure

For exposure, flood depth data for lake levels ranging from 604 ft (Lucky Climate Future) to 607.5 ft (six feet above the building standard minimum elevation) were downloaded in half-foot increments using the NOAA Lake Level Viewer, and then mapped and analyzed using ArcGIS Pro Software. The analyzed flood depth rasters were exported as TIFF files and used as hazard data inputs in FAST.

Sensitivity

Measuring sensitivity of a structure to flood impacts consisted of using structural information, such as market value, foundation type, occupancy type, replacement cost, market value, first floor height, total area of building, and number of stories. Structural information for Minnesota Point was collected from the county’s tax assessor’s office and modified to fit the formatting requirements as a .csv file for inputting into FAST. The assessor data used for this assessment was from the 2024 tax record. Replacement cost and first floor height were two structural characteristics that were not documented in the tax assessor records. Therefore, rough estimates were made for each using other structural and environmental information such as market value, foundation type, and elevation data.

Vulnerability Results

For the purposes of this study, the Project Partners measured vulnerability in the form of damages to structures in dollars. It’s important to note that the total losses under each scenario cannot be simply measured in dollar amounts alone. The impacted areas and structures have a communal, cultural, and environmental value that are not captured through this process, but should be considered when prioritizing flood mitigation efforts.

A table listing the results in terms of number of impacted structures and total flood loss in dollars for each lake level from 604 ft (Lucky Climate Future) to 607.5 (6 inches above the building standard minimum elevation) in half-foot increments can be found below in Figure 16. Total flood loss is the summation of building loss and content loss determined through damage functions in FAST. The total flood loss values are solely based on damages to structures and not other forms of infrastructure.

As you would expect, the number of impacted structures and total flood loss increase as lake levels increase. The relationship between lake levels and losses is better shown in the depth damage curve in Figure 17a. Of note, the line graph in Figure 17a is in the shape of an S-curve with a steep rise in the amount of total losses once lake levels reach between 606 to 607 ft (IGLD 1985). This assessment aligns with the city’s building code that states all new builds on Minnesota Point must have a first floor elevation of at least 607 feet (or greater), based on the equation that determines the city’s Regulatory Flood Protection Elevation. However, there are clearly structures that predate the enactment of that code that have first floors sitting below 607 feet that are revealed in this vulnerability assessment. Figure 17b breaks down the total flood losses across increasing lake levels into first, second, and third quartiles.

Vulnerability assessment results were further broken down by structure type, year built, and foundation type to see if any relationships emerge between structure sensitivity and exposure.

Vulnerability vs. Occupancy Type

As one of the sensitivity inputs, FAST requires each structure to be assigned an “Occupancy Type.” For the structures on Minnesota Point, nine occupancy types were assigned and are described in Figure 18c. These occupancy types were determined using FEMA’s classification scheme, which is outlined in the FAST help documents. It is worth noting that not all building types fit within FEMA’s classification scheme for occupancy types. For example, garages and storage sheds for individual property owners were classified as “RES2 – Manufactured Home” because they did not fit in any other category. As a part of the vulnerability assessment, the Project Partners were interested in seeing how different occupancy types fared across the climate future scenarios based on flood losses. Results are described in Figures 18a and 18b. It is important to note that most of Minnesota Point is residential; therefore, it’s expected that vulnerability assessment results will show a majority of flood losses affecting different types of residential structures.

Single family dwelling (RES1) units and manufactured homes (RES2) are consistently the most vulnerable across the climate future lake levels, with total flood damages ranging from ~$15,000 to ~$3.6 million for single family homes and ~$34,000 to ~$4.5 million for manufactured homes. This is to be expected as single family and manufactured homes together make up 83% of the structures on Minnesota Point. It’s also important to note that residential or individually owned garages and storage sheds were categorized as manufactured homes (RES2) since FEMA’s occupancy classification scheme (Figure 18c) did not have a specific category for these structures.

Vulnerability vs. Year Built

Let’s take a look at the age of the structures on Minnesota Point by comparing the year the structure was built and its exposure to rising lake levels. In theory, post-FIRM structures or structures built after 1980 should be less vulnerable to flood losses due to nationwide availability of regulatory flood maps and associated enforcement of standards and flood risk awareness. Whereas, pre-FIRM structures or structures built before 1980 should be more vulnerable to flood losses. Results are broken down by the year structures were built in Figures 19a and 19b.

As seen in the figures above, pre-FIRM structures or structures built before 1980 are consistently very vulnerable across all climate future scenarios, ranging from ~$15,000 to ~$2.7 million in damages. These pre-FIRM structures make up 72% of structures on Minnesota Point. Post-FIRM properties or structures built after 1980 are much less vulnerable, but still experience impacts at various lake levels. Structures that were built between 1980-2010 experienced significantly more damage than structures built after 2010, ranging from ~$37,000 to ~$600,000 in damages for lake levels between 604.5 and 606.5 ft high (IGLD 1985) and jumping to ~$2.7 million in damages once lake levels reach 607 ft (IGLD 1985). In 2010, Duluth enacted a building code that states all new builds on Minnesota Point must have a first floor elevation of at least 607 feet (or greater), based on the equation that determines the city’s Regulatory Flood Protection Elevation. This likely explains why there’s a significant increase in damages once lake levels reach 607 ft and why structures built after 2010 are the least vulnerable to coastal flooding based on total flood damages calculated in this assessment.

Vulnerability vs. Foundation Type

It’s also important to note that this vulnerability assessment did not have the capability to account for damages caused by wind-driven wave action, however the foundation type could have an impact on the severity of damage caused by wave action at the parcel level. Shallow foundations, like slab, fill, crawlspaces, or basement foundations, are considered the most vulnerable to wave action as they are closer to the ground surface and more susceptible to erosion and scour caused by waves, making them unsuitable for coastal construction where significant wave activity is present; in contrast, pile foundations are generally considered the most resilient option against wave action due to their deep penetration into the ground (FEMA, 2005). Results broken down by foundation type are described in Figures 20a and 20b.

According to this breakdown in total flood damages, structures with basement and slab foundations are consistently highly vulnerable across all the climate future scenarios and together make up 66% of structures on Minnesota Point. Structures with basement and slab foundations range in flood damages from $0 to ~$2.6 million. These findings are consistent with research that states shallow foundations, such as slab and basement, tend to be the most vulnerable to coastal hazards (FEMA, 2005). Structures with pier and post on ground foundations are also fairly vulnerable, ranging in flood damages from ~$0 to ~$1 million.

Mapped Vulnerable Areas on Minnesota Point

To protect property and personally identifiable information, heat maps highlighting broad areas where multiple groupings of structures were flooded under the different climate scenarios are found in Figures 21a and 21b.

Of note, all impacted structures in all scenarios are located on the harborside of Minnesota Point. This is most likely due to the fact that the shoreline on the harborside is entirely armored and experiences heavy wave reflection and erosion. Additionally, buildings are closer to the shoreline on the harborside and therefore more exposed to flood impacts.

In addition to structural damage, percent roads inundated across the different lake levels was calculated. Unfortunately, the flood damage to roads was not calculable due to the variability in material and cost of repairing and rebuilding roads. Therefore, percent of roads was the best the Project Partners could do in terms of summarizing how much of the roads would be flooded and inaccessible for emergency response units.

Figure 22b. Roads inundated under the Expected Climate Future (605 ft), Perfect Storm Climate Future (606 ft), and lake levels at 607 ft from left to right.

Reflections & Recommendations

As a barrier island, it is clear that Minnesota Point is surrounded by coastal hazards threatening its social, cultural, economic, and environmental significance for the city of Duluth and state of Minnesota as a whole. Coastal flooding and erosion are all too familiar to Minnesota Point residents with some of the more disastrous impacts occurring in recent years when more than one extratropical cyclone coinciding with a high water period hit the point, causing millions of dollars in damage and the closure of the aerial lift bridge connecting the point to the mainland.

Walking through this scenario planning process with stakeholders helped provide a creative space to think about different climate futures of varying severity and how they would impact Minnesota Point and the city of Duluth economically, socially, culturally, and environmentally. Minnesota Point is currently experiencing an influx in residents and redevelopment and has recently received new (still preliminary as of December 2024) FEMA flood maps. These recent changes compounded by current and future coastal hazards, make it even more challenging to account for uncertainty in planning for the future. This scenario planning process does a robust job of incorporating uncertainty into planning by creating a range of climate future scenarios that are grounded in historical lake level data and running a vulnerability assessment that is based on current infrastructure data.

Although this scenario planning method simplifies climate planning in ways that make it accessible to everyone, it still requires a technical skillset in GIS and GIS software for a community to implement. This is the number one limitation to this process. Relatedly, acquiring the necessary data and checking it for accuracy can be difficult. For example, county assessor data was not always accessible so alternative methods to acquire this information may have to be explored in some cases. Additionally, structure data might include duplicates that are not identifiable at first glance (e.g., garages and storage sheds may be listed separate from the main house). Other challenges might include access to local information on geomorphologic shoreline dynamics and specific flood event history. Finding a consensus on how to define the climate future scenarios with a group of stakeholders with varying perspectives and objectives was ultimately rewarding and made for a well-informed outcome, but was very challenging during the process. Finally, this scenario planning process was unable to account for the impact of wind-driven wave action due to the high variability in shoreline dynamics at the individual parcel level. This is a major limitation to this method due to the fact that wind-driven wave action can cause significant damage in addition to flooding.

Since impacts from wind-driven wave action were not included in this scenario planning process, Project Partners asked a number of subject matter experts to provide recommendations for Minnesota Point residents on ways in which they can protect themselves and their property from impacts caused by flooding and wave action. A list of those recommendations can be found below.

• Elevating structures to be above the flood risk zone. Note, residents will need to determine margin of safety by referring to Duluth’s Regulatory Flood Protection Elevation requirement mentioned above, and confer with the local floodplain manager as to which type of elevation is best for the region.
• Filling in and eliminating basements to reduce flooding risks and associated damage.
• Landscaping between building structures and shoreline may reduce wave energy and wave runup.
  • Protecting sand dunes and dune vegetation is crucial.
• Landscaping around the building to improve lot drainage using rain gardens, grading, or other low cost solutions.
• Flood proofing structures to withstand inundation.

It is strongly recommended that residents reach out to the Duluth local floodplain administrator to find more information about these strategies. Residents can also visit www.reducefloodrisk.org to explore additional strategies and determine the best path forward.

As a part of discussions throughout this process, the Project Partners asked the Minnesota Point team to consider potential climate adaptation strategies given what they learned from the scenario-planning process and the inherent environmental, social, and economic constraints on Minnesota Point. Some of the more favorable strategies were actions such as doing public outreach on coastal issues, dune system restoration, and dune preservation. A more comprehensive list of possible strategies were incorporated into and can be found in the Action Plan that was written collaboratively with the stakeholder group as a deliverable of this project.

References

Ardizone, K. A. and Wyckoff M.A. (2010). Filling the Gaps: Environmental Protection Options for Local Governments (2nd ed.). Lansing, MI: Michigan Department of Natural Resources and Environment.

Courtney, K., Geiger, J., Gonzalez, J., & Hatami, P. (2022). Rising Waters. Environmental Law & Policy Center. https://elpc.org/wp-content/uploads/2022/08/ELPCRisingWatersReport_2022.pdf

D., W., B., C., K., C., R., D.-A., & J., H. (2019). An assessment of the impacts of climate change on the Great Lakes. Environmental Law & Policy Center. https://elpc.org/wp-content/uploads/2020/04/2019-ELPCPublication-Great-Lakes-Climate-Change-Report

EPA (U.S. Environmental Protection Agency). 2014. The Great Lakes: An Environmental Atlas and Resource Book. GLERL (U.S. Great Lakes Environmental Research Laboratory). 2014. About Our Great Lakes: Great Lakes Basin Facts. MDEQ (Michigan Department of Environmental Quality). 2014. Shorelines of the Great Lakes.

FEMA. (2005). Foundations in Coastal Areas. Home Builder’s Guide to Coastal Construction. https://www.dnr.louisiana.gov/assets/docs/energy/programs/residential/coastal/hgcc_fact11.pdf

Fond du Lac Band of Lake Superior Chippewa. (n.d.). About the Onigamiinsing Dibaajimowinan. Duluth’s Stories. http://www.duluthstories.net/

Great Lakes: Lake Superior. (n.d.). Institute for Water Resources. https://www.iwr.usace.army.mil/Missions/Coasts/Tales-of-the-Coast/Americas-Coasts/Great-Lakes/Lake-Superior/

International Joint Commission. (1993). Lake Levels Reference Study: Great Lakes-St. Lawrence River Basin, Annex 2 (Land Use and Management). Working Committee 2 Final Report submitted to the Levels Reference Study Board, March 31, 1993. ISBN 1- 895085-46-2.

Louwagie, P. (2019, November 16). Duluth’s Park Point may be gradually crumbling away. Star Tribune. http://www.startribune.com/pam-louwagie/10645326/

Norton, R. K., & Meadows, G. A. (2014). Land and water governance on the shores of the Laurentian Great Lakes. Water International. https://www.tandfonline.com/doi/abs/10.1080/02508060.2014.954661

Norton, R. K., Meadows, G. A., and Lorelle A. (2011). Drawing Lines in Law Books and on Sandy Beaches: Marking Ordinary High Water on Michigan’s Great Lakes Shorelines under the Public Trust Doctrine. Coastal Management, 39: 2, 133–157.

Norton, R. K., Meadows G.A., and Lorelle A. M. (2013). The deceptively complicated ‘elevation ordinary high water mark’ and the problem with using it on a Great Lakes shore. Journal of Great Lakes Research 39(2013):527-535.

US Army Corps of Engineers, Detroit District, and Great Lakes Commission. (1999). Living with the Lakes: Understanding and Adapting to Great Lakes Water Level Change. ISBN 0-9676123-0-6.

Watras, C. J., J. S. Read, K. D. Holman, Z. Liu, Y.-Y. Song, A. J. Watras, S. Morgan, and E. H. Stanley. (2014). Decadal oscillation of lakes and aquifers in the upper Great Lakes region of North America: Hydroclimatic implications. Geophys. Res. Lett., 41, 456–462, doi:10.1002/2013GL058679.

Wilcox, D. A., Thompson, T. A., Booth, R. K., & Nicholas, J.R. (2007). Lake-Level Variability and Water Availability in the Great Lakes. USGS Publications Warehouse. https://pubs.usgs.gov/circ/2007/1311/pdf/circ1311_web.pdf

Wisconsin’s changing climate: Impacts and solutions for a warmer climate. (2021). Wisconsin Initiative on Climate Change Impacts. Nelson Institute for Environmental Studies, University of Wisconsin-Madison and the Wisconsin Department of Natural Resources, Madison, Wisconsin. https://wicci.wisc.edu/2021-assessment-report/

Wuebbles, D., Cardinale, B., Cherkauer, K., Davidson-Arnott, R., Hellmann, J., Infante, D., & Ballinger, A. (2019). An assessment of the impacts of climate change on the Great Lakes. Environmental law & policy center, 104(3-4), 629-652.

Appendix I: Data Types and Sources used in the Scenario Planning Process

Appendix II: Definitions of Relevant Terms

Base Flood

A flood that has a 1-percent chance of occurring during any given year. The area at risk from the base flood is called the Special Flood Hazard Area (SFHA). Properties within the SFHA are at a high risk of flooding, with at least a 26-percent chance of flooding over the course of a 30-year mortgage.

Base Flood Elevation

The Base Flood Elevation (BFE) is how high floodwater is likely to rise during a 1-percent-annual-chance flood event. BFEs are measured from a reference point called NAVD88, which is approximately equal to sea level, and vary widely across geographies.

Coastal Flooding

Coastal floods come from sources such as the Atlantic and Pacific Oceans, the Gulf of Mexico and large lakes (such as the Great Lakes), bays, and tidal rivers that are big enough to have large waves or that can be affected by storm surge. Coastal floods can be very dangerous when high waters are combined with the destructive forces of waves. In low-lying coastal areas, storm surge and flooding can reach many miles from the shoreline, flowing up rivers and across flat land.

Erosion

On the Great Lakes shoreline, erosion refers to the wearing away of beaches, dunes, or bluffs by the forces of waves, flowing water, and/or winds. During storm events, a lot of erosion can happen in a short time, causing stark changes to the coastline. Erosion cuts into dunes and bluffs, causing roads and buildings built upon them to collapse. Smaller dunes may be completely washed away, allowing water and waves to flow inland and flood the areas behind them.

Expected Climate Future

Represents average lake levels with some influence from an extratropical storm. The maximum flood elevation for the Expected Climate Future is 605 ± 0.1 ft (IGLD 1985).

Inundation

Flooding; in other words, water covering normally dry land.

International Great Lakes Datum (IGLD)

A common reference system used to measure water level heights throughout the Great Lakes, their connecting waterways, and the St. Lawrence River System.

Limit of Moderate Wave Action (LiMWA)

Flood maps in coastal areas may include a line called the Limit of Moderate Wave Action (LiMWA). The LiMWA marks the inland limit of the “Coastal A Zone,” a term referenced by building codes and standards. The Coastal A Zone is the part of the coastal SFHA where wave heights can be between 1.5 and 3 feet during the base flood event. Because of the higher risk of damage to homes and other structures from waves in the Coastal A Zone, FEMA encourages the practice of building to Zone V standards within this area.

Low Water Datum (LWD)

A surface that is so low that the water level rarely falls below it. Different LWD surfaces are used for different lakes and rivers. Sea level is equal to zero.

Lucky Climate Future

Represents low lake levels with some influence from an extratropical storm. The maximum flood elevation for the Lucky Climate Future is 604 ± 0.1 ft (IGLD 1985).

Ordinary High Water Mark (OHWL)

The boundary of public waters and wetlands, and shall be an elevation delineating the highest water level which has been maintained for a sufficient period of time to leave evidence on the landscape, commonly that point where the natural vegetation changes from predominantly aquatic to predominantly terrestrial. For water courses, the ordinary high water level shall be the elevation of the top of the bank of the channel. For reservoirs and flowages, the ordinary high water level shall be the operating elevation of the normal summer pool.

Perfect Storm Climate Future

Represents high lake levels with some influence from an extratropical storm. The maximum flood elevation for the Perfect Storm Climate Future is 606 ± 0.1 ft (IGLD 1985).

Primary Frontal Dune (PFD)

A Primary Frontal Dune (PFD) is the first line of defense against coastal flooding. The dune is a mound or ridge of sand that generally runs parallel to the shoreline along the back of the beach. PFDs act as a “sacrificial area” by providing a large amount of sand for waves to crash into before the waves reach developed areas and cause damage to buildings and roads. On flood maps, PFDs are mapped as Zone V or VE. FEMA regulations do not allow any man-made changes to the dune that could make coastal floods even more damaging.

Stillwater Elevation

The elevated water level at the coast is a major component of coastal flooding. Elevated water levels allow floodwaters and waves to travel further inland than they would otherwise. In the context of FEMA coastal flood studies, the elevated water level observed during a flood event is usually called the stillwater elevation. The stillwater elevation tells us how high flood waters could rise during a flood event due to storm surge, tides, wave setup, or other factors that cause water levels to increase, such as seasonal effects. The higher the stillwater elevation, the farther inland the impacts of flooding will be felt. The stillwater elevation does not include the additional height of waves that ride on top of the water’s surface.

Storm Surge

When a storm approaches the coast, strong winds push water towards land and cause a rise in the water level. This is called storm surge. Storm surge can cause major coastal and inland flooding. The amount of storm surge in an area depends on many things, including the size and strength of the approaching storm, where it is going and how fast it is moving, and the shape of the coastline. Because of this, the same storm can cause different levels of storm surge along the same coastline. Storm surge can be incredibly dangerous because water levels may rise very fast, even before a storm makes landfall.

Total Flood Loss

Total flood loss values for each storm-related climate future are the summation of damages to structures and damages to contents within structures.

Zone AE

A high-risk flood zone designated by the Federal Emergency Management Agency (FEMA) where there is a 1% chance of flooding annually. This means that there is a 26% chance of flooding over the course of a 30-year mortgage. Zone AE areas are also known as Special Flood Hazard Areas (SFHA) and are often located near bodies of water such as rivers, lakes, and floodplains.

Zone AO

River or stream flood hazard areas, and areas with a 1% or greater chance of shallow flooding each year, usually in the form of sheet flow, with an average depth ranging from 1 to 3 feet. These areas have a 26% chance of flooding over the life of a 30-year mortgage.

Zone VE

Coastal areas with a 1% or greater chance of flooding and an additional hazard associated with storm waves. These areas have a 26% chance of flooding over the life of a 30-year mortgage. Base flood elevations derived from detailed analyses are shown at selected intervals within these zones.

Zone X

Area of minimal flood hazard, usually depicted on FIRMs as above the 500-year flood level.

Appendix III: Important Resources

Appendix IV: Maps

Map 1a: Three Climate Future Scenarios with Ordinary High Water Mark – Large Scale

Map 1b: Three Climate Future Scenarios with Ordinary High Water Mark – Small Scale

Map 2a: Lucky Climate Future with Ordinary High Water Mark – Large Scale

Map 2b: Lucky Climate Future with Ordinary High Water Mark – Small Scale

Map 3a: Expected Climate Future with Ordinary High Water Mark – Large Scale

Map 3b: Expected Climate Future with Ordinary High Water Mark – Small Scale

Map 4a: Perfect Storm Climate Future with Ordinary High Water Mark – Large Scale

Map 4b: Perfect Storm Climate Future with Ordinary High Water Mark – Small Scale

Map 5: Vulnerability Assessment Results for 605 ft (Expected)

Map 6: Vulnerability Assessment Results for 605.5 ft (Expected plus six inches)

Map 7: Vulnerability Assessment Results for 606 ft (Perfect Storm)

Map 8: Vulnerability Assessment Results for 606.5 ft (Perfect Storm plus six inches)

Map 9: Vulnerability Assessment Results for 607 ft

Map 10: Vulnerability Assessment Results for 607.5 ft