To understand where and how coastal communities might be at risk of storm-induced wave run-up, aggressive erosion, and flooding, analysts must understand the unique dynamics of high-energy wave action and flooding along Great Lakes shorelines and nearshore rivers. This chapter provides a brief “primer” on Great Lakes coastal dynamics and describes the impacts the Great Lakes region may experience from climate change in the foreseeable future. Additionally, the chapter includes a detailed step-by-step guide for community planners to develop their own set of planning scenarios that incorporate wave-action and flooding risks using publicly available data.
Methods for identifying high risk coastal areas can be derived from a combination of available data and reasonable assumptions about future water levels and storminess. The methods presented here essentially create two maps based on two discrete analyses and then “knits” them together. The first map focuses on a Great Lakes shoreline analysis, while the second focuses on a coastal area riverine-analysis.
For the technical methodology, download the Identifying High-Risk Flood Areas technical guide.
Background and Considerations
Great Lakes Dynamics
In terms of hydrology, coastal dynamics, and geology, the Great Lakes function differently from other inland water bodies and tidal oceans. Water level changes within the Great Lakes result not from the moon’s gravitational pull, but from cyclical changes in rainfall, evaporation, and riverine and groundwater inflows and outflows.(1) These factors work together to incrementally raise and lower the lakes’ standing water levels over a combination of daily, seasonal, annual, and decadal cycles.
Decadal and multi-decadal shifts in water levels alone are not responsible for all of the shoreline’s landward and lakeward movements. Rather, the velocity and height of waves, erosion-induced recession of shorelines, and variability in the oscillation of water levels also contribute to Great Lakes’ coastal dynamics, taken altogether.
Long-term Water Level Oscillations
The long-term standing water levels of all of the Great Lakes can fluctuate by multiple feet over the course of decades. Between October 1986 and January 2013, for example, the standing water level of Lakes Michigan and Huron dropped from an all-time high of 582.35 ft. above the International Great Lakes Datum (1985) — an approximated benchmark above sea level — to an all-time low of 576.02 ft. IGLD (1985), a drop of about 6 feet. After January 2013, the lakes began climbing rapidly, reaching 582.18 ft. IGLD (1985) again by June 2020.(2) While these fluctuations encompass the extremes that have been experienced in recorded history on the lakes over the past century, those recorded historical patterns suggest that similar fluctuations, if somewhat unpredictable in timing and extent, will continue.(3)
High Energy Waves
The Great Lakes are subject to high energy waves and wave run-up along the coastline. High energy waves are strong in speed and intensity, created primarily as fast winds move across the surface of the water for extended distances.(4) Wave setup refers to the height of the water as waves reach the shore. High wave setup results as regional storm patterns create high winds on the bounded water bodies of the Great Lakes. These powerful and tall waves are natural conditions that can increase the pace of erosion and damage structures on or near the shoreline.(5)
Coastal Erosion and Shoreline Recession
The shorelines of Lake Michigan are mostly made of gravel and sands that easily erode during times of high energy waves.(6) Aggressive coastal erosion, a natural occurrence on the geologically young Great Lakes, can result in near-term submergence of shoreland, resulting in turn in flooding and damage to infrastructure along bluffs and beaches. Erosion also causes the gradual recession of the shoreline landward over the long term. Erosion is caused mainly by storms and winds, not necessarily by rising lake levels directly, but its impacts are generally felt more strongly when lake levels are high.(7)
The Great Lakes are contained in gradually shifting and tilting basins. This tilting results as the Earth slowly decompresses and rebounds from the immense weight of the glaciers that created the Great Lakes.(8,9) These changes are accounted for periodically through adjustment to the IGLD, but the presence of this feature and its uneven distributional effects across the basin contribute to the difficulty of predicting the pace of shoreline movement. Therefore, it is safest to plan for high levels of variability and rapid change in water levels over time.(10)
Powerful waves, erosion, and quickly changing shorelines are natural processes of the Great Lakes, each having implications for planning efforts along the coast. Climate change, however, intensifies these natural processes, and requires preemptive planning in coastal communities.
Globally, evidence collected over the last 150 years shows a trend toward a higher global temperatures, higher sea levels, and less snow cover in the Northern Hemisphere. Scientists and ecologists have observed and documented significant changes in the Earth’s climate. The warming of the climate system is unequivocal and is now expressed in higher air and ocean temperatures, rising sea levels, and melting ice.(11) Looking at climate change impacts upon the Great Lakes region specifically, scientists expect that climate change will result in increased temperatures and more frequent and intense storms across the region. It will not not result in the perpetual rise of lake levels akin to sea level rise (the lakes are not connected to the melting polar ice caps), but lake level fluctuations – as described above and discussed more below – are expected to continue.
WEATHER VS. CLIMATE: It is important to note that “climate” and “weather” are directly related, but are not the same thing. Weather refers to the day-to-day conditions in a particular place, like sunny or rainy, hot or cold. Climate refers to the long-term patterns of weather over large areas. When scientists speak of “global climate change,” they are referring to changes in the generalized, regional patterns of weather over months, years and decades. Here, when we discuss “climate change,” we refer to the ongoing change in a region’s general weather characteristics or averages. In the long term, a changing climate will have more substantial effects on the Great Lakes than individual weather events.
As reported by the Great Lakes Integrated Sciences & Assessments Center (GLISA), the Great Lakes region experienced a 2.3 degree Fahrenheit increase in average air temperatures from 1900 to 2012.(12, 13) An additional increase of 1.8 to 5.4 degrees Fahrenheit in average air temperatures is projected by 2050. Although these numbers appear relatively small, they are driving very dramatic changes in Michigan’s climate and will significantly impact the Great Lakes.(14)
Storm Frequency and Intensity
There is strong consensus among climate experts that storms, greater in number and intensity, will occur in the Great Lakes region.(15) This is already happening as “the amount of precipitation falling in the heaviest 1% of storms increased by 37% in the Midwest and 71% in the Northeast from 1958 to 2012.”(16) As storms drop more precipitation and generate stronger sustained winds, the Great Lakes will see stronger and higher waves.(17) In addition to direct damage caused by storms, sustained increases in the number of storms and their intensity can both directly and indirectly pollute waters by overloading sewage and stormwater capabilities.(18) Increases in the intensity of storms also quickens the pace of erosion on Great Lakes shorelines. In fact, the Federal Emergency Management Agency (FEMA) projects approximately 28% of structures within 500 feet of a Great Lakes shoreline are susceptible to erosion by 2060.(19)
The natural ups and downs in Lake Michigan’s water levels will continue regardless of climate change.(20) However, climate change is likely to amplify this natural process, creating more variable water levels as warmer air temperatures result in fewer days of ice cover and faster evaporation.(21) In other words, lake levels could rise and fall faster and with even less predictability than they have in the past.(22)
Fast-rising waters can erode shorelines, damage infrastructure, and cause extensive flooding in inland rivers.(23) When lake levels fall, access to infrastructure like docks may be restricted and navigation hazards in shallow waters are exposed. Low lake levels pose a threat to coastal vegetation and can reduce the pumping efficiency of drinking water intake pipes.(24) Additional ramifications of changing lake levels include a drop in water supply, restricted fish habitats, more invasive species, faster erosion, and an overall decline in the ecological health of beaches.(25, 26) Climate change is likely to augment the natural highs and lows of lake levels, causing more variability and a faster rate of change, making each of these potential ramifications both more likely and less predictable.
Data Sources that Will be Used for this Analysis
The spatial boundaries of high risk coastal areas associated with the three climate futures in this scenario-based planning method are crafted using publicly available data from the following federal and state agencies:
Federal Emergency Management Agency (FEMA)
FEMA’s Flood Insurance Rate Maps (FIRMS) are a floodplain management tool that depict special hazard areas and the risk premium zones. These maps are used to help officials identify a community’s flood risks and inform homeowners of insurance obligations for their property. There are various flood zones (i.e. A, AE, etc.) within these maps, which play a role in the composition of each of the climate futures. FIRMs are available as a free download from FEMA’s website in digital format as PDFs and GIS shapefiles.
Great Lakes Environmental Research Laboratory (GLERL)
As a section of the National Oceanic and Atmospheric Administration (NOAA),GLERL conducts environmental research on the Great Lakes and coastal regions. The historic water levels of all five Great Lakes (plus Lake St. Clair) are available at their online dashboard (https://www.glerl.noaa.gov/data/dashboard/GLD_HTML5.html), which provides reasonable stillwater benchmarks (historic high, average, and low) for crafting realistic climate futures.
United States Geological Survey (USGS)
USGS is the science agency for the Department of the Interior. As the nation’s largest water, earth, and biological science and civilian mapping agency, USGS collects, monitors, analyzes, and provides science about natural resource conditions, issues, and problems. The amount of information available through the USGS is incredibly vast, from the migratory patterns of birds to the locations of mining operations. One very useful resource provided by the USGS is their Digital Elevation Model (DEM), which maps out the elevations for areas throughout the US. Paired with historical or predicted flood elevations, this data layer can help identify areas at risk given a particular climate future.
Great Lakes Aquatic Habitat Framework (GLAHF)
The GLAHF is a comprehensive database for Great Lakes ecological data operated by the University of Michigan and the Michigan Department of Natural Resources. The GLAHF website contains interactive maps depicting a number of variables one might consider when identifying high risk areas such as wave height, shoreline material, and the location of wetlands. There is also additional information available related to environmentally sensitive areas within the Great Lakes. All data sets are downloadable as GIS Geodatabase files.
(1) Norton, Richard K. , Meadows, Lorelle A. and Meadows, Guy 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. Gronewold, Andrew .D., et al. (2013). ‘Coasts, water levels, and climate change: A Great Lakes perspective. Climatic Change, 120:697-711.
(2) National Oceanic and Atmospheric Administration. (n.d.). NOAA Great Lakes Environmental Research Laboratory (GLERL) Great Lakes Dashboard. Retrieved September 19, 2019, from https://www.glerl.noaa.gov/data/dashboard/GLD_HTML5.html
(3) Meadows, Guy A., and Meadows, Lorelle A., Wood, W.L., Hubertz, J.M., Perlin, M. “The Relationship between Great Lakes Water Levels, Wave Energies, and Shoreline Damage.” Bulletin of the American Meteorological Society Series 78: 4. (1997): 675-683. Print.
(4) National Oceanic and Atmospheric Administration. “Coastal Currents.” Ocean Service Education. NOAA, 25 March 2008. Web. Accessed July 2015.
(5) Norton, Richard K. , Meadows, Lorelle A. and Meadows, Guy 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, First published on: 19 February 2011 (iFirst)
(6) Norton, Richard K. , Meadows, Lorelle A. and Meadows, Guy 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, First published on: 19 February 2011 (iFirst)
(7) Meadows, Guy A., and Meadows, Lorelle A., Wood, W.L., Hubertz, J.M., Perlin, M. “The Relationship between Great Lakes Water Levels, Wave Energies, and Shoreline Damage.” Bulletin of the American Meteorological Society Series 78: 4. (1997): 675-683. Print.
(8) Dorr, J. A., and D.F. Eschman. 1970. Geology of the Great Lakes. Ann Arbor: University of Michigan Press.
(9) Wilcox, D.A, Thompson, T.A., Booth, R.K., and Nicholas, J.R., 2007, Lake-level variability and water availability in the Great Lakes: U.S. Geological Survey Circular 1311, p. 25
(10) Wilcox, D.A, Thompson, T.A., Booth, R.K., and Nicholas, J.R., 2007, Lake-level variability and water availability in the Great Lakes: U.S. Geological Survey Circular 1311, p. 25
(11) Intergovernmental Panel on Climate Change. (2007). Observed changes in climate and their effects. Web. Accessed July 2015.
(12) The Great Lakes Integrated Sciences & Assessments Center (GLISA is a consortium of scientists and educators from the University of Michigan and Michigan State University, provides climate models for the Great Lakes Region in support of community planning efforts.
(13) Great Lakes Integrated Sciences and Assessments (2015). Temperature. Web. Accessed July 2015.
(14) Great Lakes Integrated Sciences and Assessments (2015). Temperature. Web. Accessed July 2015.
(15) U.S. Global Change Research Program. Global Climate Change in the United States, 2009. Cambridge University Press, Cambridge
(16) Mackey, S. D., 2012: Great Lakes Nearshore and Coastal Systems. In: U.S. National Climate Assessment Midwest Technical Input Report. J. Winkler, J. Andresen, J. Hatfield, D. Bidwell, and D. Brown, coordinators.
(17) Great Lakes Integrated Sciences and Assessments. Climate Change in the Great Lakes Region. GLISA, 2014. Web. Accessed July 2015.
(18) Cruce, T., & Yurkovich, E. (2011). Adapting to climate change: A planning guide for state coastal managers–a Great Lakes supplement. Silver Spring, MD: NOAA Office of Ocean and Coastal Resource Management
(19) The Heinz Center. (2000). Evaluation of Erosion Hazards. Web. Accessed July 2015.
(20) Dinse, Keely. Preparing for Extremes: The Dynamic Great Lakes. Michigan Sea Grant. Web. Accessed July 2015.
(21) Cruce, T., & Yurkovich, E. (2011). Adapting to climate change: A planning guide for state coastal managers–a Great Lakes supplement. Silver Spring, MD: NOAA Office of Ocean and Coastal Resource Management.
(22) Dinse, Keely. Preparing for Extremes: The Dynamic Great Lakes. Michigan Sea Grant. Web. Accessed July 2015.
(23) Dinse, Keely. Preparing for Extremes: The Dynamic Great Lakes. Michigan Sea Grant. Web. Accessed July 2015.
(24) Dinse, Keely. Preparing for Extremes: The Dynamic Great Lakes. Michigan Sea Grant. Web. Accessed July 2015.
(25) Cruce, T., & Yurkovich, E. (2011). Adapting to climate change: A planning guide for state coastal managers–a Great Lakes supplement. Silver Spring, MD: NOAA Office of Ocean and Coastal Resource Management.
(26) Dinse, Keely. Preparing for Extremes: The Dynamic Great Lakes. Michigan Sea Grant. Web. Accessed July 2015.