Section 1: Potential Risks and Impacts Background

This section focuses on anticipated environmental and climate-related changes as an operational issue and lays a foundation for how your operation can address such changes in a way that makes sense to your facility’s bottom line. The three major environmental and climate-related changes most relevant to ports, harbors and marinas are:

  • Fluctuations in water level
  • Storm frequency and intensity
  • Changing precipitation and temperature

Great Lakes Region Climate Trends

A summary of recent scientific findings reports: “Intense rainstorms, floods and heat waves will become more common in the Great Lakes region due to climate change in the coming decades. While ice-cover declines will lengthen the commercial navigation season on the lakes, warmer lake temperatures will increase risks from invasive species, and could threaten water quality.”

Source: GLISA Synthesis of the National Climate Assessment for the Great Lakes Region, 2014

When considering the impact of changing environmental conditions on your facility, it may be helpful to assess your current goals, strategies and operating procedures in the context of increasingly variable conditions. What impacts do you need to prepare for? What will more intense and frequent storms do to your infrastructure? How will you respond to fluctuating water levels? How would shifts in weather patterns affect your shoulder seasons and staffing needs?

This section includes information on the risks and impacts most relevant to waterfront operations, background information, and a list of tools and resources for each topic. Generally, the “tools” are interactive resources provided to help you explore an issue further and the “resources” are available to summarize findings.

Learning Objectives

By the end of this section, you should be able to:

  • Understand and recognize potential risks and impacts to your facility.
  • Identify tools to learn more about potential risks.



Fluctuating Water Levels

Water levels directly affect marinas and harbors in the Great Lakes. Physical access to boat slips, navigation channels and harbors of refuge may be compromised. Fluctuating water levels influence a facility’s ability to operate, and in turn, affect finances and patronage. Operators generally acknowledge that facilities are adversely affected by decreases in lake levels: expenses are incurred through damages, adaptations and lost slip rental revenue. High water levels may be problematic and require adaptations or related repairs, especially during storm surges, but may not be as immediately damaging as low levels.

How Water Levels Affect Marinas and Harbors

Fluctuating water levels — both higher and lower — will affect your facility. For example, given a 3 foot drop in water levels, a recent study projected cost estimates ranging from $53,000 to $83,000 per marina depending on the lake. Some impacts from drastically different water levels will be experienced regardless of whether levels are higher or lower; additional impacts are specific to whether levels are higher or lower. The following table provides an overview of potential impacts.

Environmental Change Potential Impact
Fluctuating Water Levels
  • Reduced stability and strength of dockage and increased rate of deterioration for dockage.
  • Increased need for dredging to harbor navigation channels and interior facility slips.
  • More/less beach area and related aesthetic issues.
  • Variation in nearshore habitat impacting desired and nuisance species (e.g., fish spawning habitat and related tourism; increased populations of invasive species).
  • Increased costs from additional dredging, permanent adaptations and operational changes.
Lower water levels
  • Existing structure undermined (exposure of wood frames to oxygen increases rate of decay).
  • Potential safety concerns (increased vertical distance between fixed dock and vessel, vessels running aground or striking bottom).
  • Stranded dock or harbor in extreme lows.
  • Bottleneck at channel entry/exit (boater wait time).
  • Reduced access to slips (limits on size of vessel entering basin, reassignment of berths to match draft depths).
  • Increased need for dredging.
  • Reduced access to boat launch (ramp not long enough).
  • Increase in costs: dredging, permanent adaptations (e.g., floating docks), accepting only smaller boats with a loss of revenues from slip fees and other purchases (e.g., fuel and groceries).
Higher water levels
  • Stability and strength of infrastructure compromised and structures may become unusable in extreme conditions (e.g., storm surges).
  • Widespread shoreline erosion and flooding.
  • Greater potential for flooding of critical land areas and operational structures.
  • Reduced beach access, limiting recreational activities.
  • Changes to ecology of beach and offshore habitat, affecting aesthetics and fisheries.
Sources: Climate Change and Wisconsin’s Great Lakes Coastal Communities, Wisconsin Initiative on Climate Change Impacts; NOAA Water Levels Briefing: November 20, 2013; Recreational Boating and Tourism Contextual Narrative; International Upper Great Lakes Study


Understanding Fluctuating Water Levels

When assessing your facility’s risk to fluctuating water levels, it may be helpful to consider the historic range of highs and lows — there are no guarantees that future conditions will remain in this range, but it is a good starting point when considering how to prepare for extremes. The U.S. Army Corps of Engineers’ report differences between record high and low monthly mean lake levels as:

  • Superior: 3.9 ft (1.2 meters)
  • Michigan/Huron: 6.3 feet (1.9 meters)
  • Erie: 6.1 ft (1.8 meters)
  • Ontario: 6.6 ft (2.0 meters)
Source: USACE Long-term Averages for Great Lakes Water Levels (PDF), 2013

The Great Lakes Water Budget

The Great Lakes Water Budget Precipitation, evaporation and runoff are shown for each Great Lake using orange, red and green arrows, respectively. Large blue arrows represent basin-wide evaporation and precipitation. Because nearly a third of the surface area of the Great Lakes basin is water (unique for a basin of this size), the three primary components (evaporation, precipitation and runoff) are roughly equal in their influence on the water budget. Source: U.S. EPA 2012.

Great Lakes water levels do not rise and fall with individual storms, but rather, significant water level fluctuations require months, seasons or years of wet or dry conditions. Lake levels are determined by three main factors related to inputs and outputs (i.e., the water budget):

  • Evaporation off the lakes and evapotranspiration from land
  • Precipitation onto land and lakes
  • Runoff from the land and rivers into the lakes

These factors, each equal in their influence on the water budget, are influenced by changes in climate. Annual average air and water temperatures are rising and future climate models project continued warming, which contributes to higher rates of evaporation.

Projected future precipitation amount, rates and annual variability in timing of wetter and drier periods vary by model, and scientists are currently unsure if the increase in evaporation will be offset by an increase in precipitation. Seasonal changes in water level are driven by fluctuations in evaporation, ice cover and precipitation, so researchers continue to explore this relationship.

Water levels are also influenced by glacial isostatic adjustment (tilting of basin), ice cover and seasonal variations. While the relationship between ice cover, evaporation and water levels is complex, typically heavy ice cover can reduce the amount of evaporation from the Great Lakes in the fall and winter, thus contributing to higher water levels in the future. (If a lake is residually cold from a prior winter’s extreme ice cover, evaporation which typically peaks in fall, may be reduced.)

Seasonal changes in weather patterns, which influence evaporation and precipitation, typically cause an annual pattern of rising and falling of Great Lakes water levels:

  • A seasonal rise in the spring — primarily caused by an increase in precipitation, the melting of accumulated snow, an increase in runoff and low evaporation rates.
  • A seasonal decline in the fall and winter — primarily caused by an increase in evaporation, a decrease in precipitation and the accumulation of snowpack on the land area.


Interactive Tools

You can use the following tools to learn more about fluctuating water levels, informing your assessment of your facility’s risks and impacts.

Great Lakes Dashboard Project chart

Great Lakes Water Level Dashboard: View current, historical and projected water levels. The NOAA Great Lakes Environmental Research Laboratory’s Great Lakes Water Level Dashboard provides a way to visualize and examine historic lake levels and future projection comparisons at different times. Options are available for customizing graphs. Also check out the new Great Lakes Hydro-Climate Dashboard, a build-on to the original dashboard that includes data on drivers behind water level change, like precipitation, evaporation and ice cover data.

lakelevelsGreat Lakes Lake Level Viewer: A visualization tool produced by the NOAA Office for Coastal Management that can be used to gain a better perspective on changing lake levels. Interactive images of local community landmarks together with maps showing water level scenarios convey the potential physical, social and economic impacts of lake level change in the U.S. Great Lakes.



  • Summary Reports: Six Month Forecast Bulletins (USACE)
    U.S. Army Corps of Engineers webpage home for downloadable bulletins including hydrographs depicting water levels for the previous year, the current year to date and a projection for the next six months (based on present condition of lake basin and anticipated future weather).
  • Connecting Channels Forecast (USACE): Chart view of expected water levels in next four weeks for all Great Lakes and connecting channels (St. Lawrence River, Detroit River, St. Clair River, St. Marys River).
  • Water Level Summaries (USACE): Brief monthly summaries (PDF) of water levels and conditions for each of the Great Lakes. Includes mean water level, how it changed from prior month, relationship to long-term average, expectations for coming months and notable conditions (e.g., above-average precipitation for a lake basin).
  • Great Lakes Data: Great Lakes Water Quality (NOAA) – HABs, hypoxia, beach water quality.
  • Technical Observations: CoastWatch – Great Lakes (NOAA)- Near real-time observation and tracking for a number of physical characteristics in the Great Lakes
    • Great Lakes Surface Environmental Analysis (GLSEA) – Imagery of surface water temperatures, and imagery for ice cover, as applicable.
    • Great Lakes Surface Water Temperatures – Local contour maps for Great Lakes surface water temperatures (produced in partnership between NOAA and Michigan Sea Grant)
    • In Situ Data – Current wind and wave conditions and forecasts, plus weather report
    • Geostationary Operational Environmental Satellite (GOES) – Current satellite imagery
  • Video: Great Lakes Water Level Changes: Addressing Risks and Impacts on Coastal Assets (NOAA and TNC)
    Learn how changing water levels impact economics, nature and infrastructure in the Great Lakes basin and how decision makers can use tools and data to promote more resilient communities. (5 minutes)
  • Video Series: Unchartered Waters: Journal Sentinel Special Report (Milwaukee Journal Sentinel)
    Series of videos developed as part of a special report on water levels in the Great Lakes.
  • Video: Great Lakes Ice and Water Levels (University of Michigan Engineering)
    Discussion of implications of ice cover and frigid water on the lakes’ future water levels and shipping and tourism industries that depend on them; plus efforts to obtain better ice and water level measurements. (3.5 minutes)
  • Website: Great Lakes Ice Cover (NOAA)
    NOAA resources on exploring the relationships between ice cover, lake thermal structure, and regional climate.

Storm damage from Hurricane Sandy at a Lake Erie marina.

Storm damage from Hurricane Sandy at a Lake Erie marina. Source: Ohio Department of Natural Resources.

Increased Storm Frequency and Intensity with Increased Precipitation

Storms are becoming more frequent and more intense, escalating the risk for damage at marinas and harbors. In 2012, Hurricane Sandy delivered gale force winds over 45 miles per hour causing damage to marinas and breakwaters along the Lake Erie shoreline; the storm also increased sediment loads to harbors and channels. In some marinas, damage to patron’s vessels was extensive and operators and owners have spent months afterward determining legal responsibilities and conducting clean-up. Future storms will pose similar operational considerations.

How Storms and Precipitation Affect Marinas and Harbors

Increased storm frequency and intensity will affect your facility. The following table provides an overview of potential impacts.

Environmental Change Potential Impact
Increased Storm Frequency and Intensity
  • Larger waves, higher seiches and greater storm surges can damage port and harbor infrastructure.
  • Increased potential for shoreline erosion and damage to existing property due to erosion from storm runoff and flooding.
  • Increased need for scour protection at the base of fixed docks, piles and walls.
  • Damage to dockage and boats while moored.
  • Vessel maneuverability and speeds affected, potentially raising safety concerns.
  • Increased channel sedimentation or resuspension, plus potential for resuspension of contaminated sediments.
Increased Precipitation
  • Increased rainfall amounts may overwhelm onsite stormwater management system, resulting in flooding.
  • Impaired water quality and beach closures if increased runoff deposits excess nutrients and pathogens on beach (e.g. combined sewer overflow), resulting in economic loss.
  • Prolonged dry periods can lead to major slope failures in heavy rainfall events.
Sources: Climate Change Implications and Adaptation Strategies , Wisconsin Sea Grant; Climate Change and Wisconsin’s Great Lakes Coastal Communities, Wisconsin Initiative on Climate Change Impacts; Midwest Climate Impacts, ICLEI


Understanding Storms and Precipitation

Extreme rainfall events and flooding have increased in frequency during the last century, and these trends are expected to continue. In the Midwest, the 10 rainiest days can contribute as much as 40 percent of total precipitation in a given year. Generally, annual precipitation increased during the past century — by up to 20 percent in some locations — with much of the increase driven by intensification of the heaviest rainfalls (National Climate Assessment, 2014).

Flooding also causes major human and economic consequences, including disruption to navigation in the region’s roads, rivers and reservoirs. Furthermore, water infrastructure for flood control, navigation, and other purposes is susceptible to climate change impacts and other forces because the designs are based upon historical patterns of precipitation and stream flow—which may no longer be appropriate guides in a changing climate (GLISA, 2014).


Interactive Tools

You can use the following tools to learn more about storm frequency and intensity, informing your assessment of your facility’s risks and impacts.

  • Flood Map Service Center (FEMA): provides access to your official flood map, a range of other flood hazard products and tools to support a better understanding of flood risk.

FEMA’s Flood Maps: Know Your Risk and Take Action Against Flooding infographic to learn more about how flood maps are developed and used to determine flood insurance rates through the National Flood Insurance Program.



  • Map: Projected Precipitation Changes in the Midwest: Interactive Map (U.S. Global Change Research Program – Midwest Report)
    Map showing change in average precipitation, increases in the amount of rain falling in the wettest 5-day period over a year; also the differences in number of days with heavy precipitation (top 2% of all rainfalls each year) and number of consecutive dry days.
  • Website: National Flood Insurance Program: Flood Hazard Mapping (FEMA)
    Through its Flood Hazard Mapping Program, also known as Risk Mapping, Assessment and Planning (Risk MAP), FEMA identifies flood hazards, assesses flood risks and partners with states and communities to provide accurate flood hazard and risk data to guide them to mitigation actions. Risk MAP provides high quality flood maps and information, tools to better assess the risk from flooding plus planning and outreach support. Each Risk MAP flood risk project is tailored to the needs of each community and may involve different products and services.

Temperature Changes

Changes in our region’s temperatures will affect recreational boating and facilities operation in several ways. It’s not all bad news, as the boating season may be extended if temperatures warm. At the same time, operators will need to be aware of the impact of launching boats in an early warm period followed by a late spring freeze.

How Temperature Affects Marinas and Harbors

Changes in precipitation and temperature averages and extremes will affect your facility. The following table provides an overview of potential impacts.

Environmental Change Potential Impact
Temperature Changes
  • Increased wear on buildings due to heat and weather extremes.
  • Increased annual energy costs due to probable need for additional air conditioning during summer.
  • Shorter winters may extend boating season, influencing operations (start date for seasonal staff, varying dates launch/storage of vessels).
  • Late spring freezes may impact boats dewinterized and launched in an early warm period.
  • Increased heat wave intensity and frequency plus increased humidity could bring more people to the waterfront.
  • Changes in freeze-thaw cycles may adversely affect bluff stability and accelerate slope erosion processes.
Sources: Climate Change Implications and Adaptation Strategies, Wisconsin Sea Grant; Climate Change and Wisconsin’s Great Lakes Coastal Communities, Wisconsin Initiative on Climate Change Impacts; Midwest Climate Impacts, ICLEI

Midwest Annual average temperatures chart

Temperatures are rising in the Midwest. Annual average temperatures (red line) across the Midwest show a trend towards increasing temperature. The trend (heavy black line) calculated over the period 1895-2012 is equal to an increase of 1.5°F. (Figure source: GLISA, updated from Kunkel et al. 2013).

Understanding Temperature

Key precipitation and temperature changes anticipated for the Great Lakes region include increased number and intensity of heat waves and increased humidity. Variations in timing of temperature changes are also expected, including more late spring freezes and decreased ice cover. The Midwest, which includes much of the Great Lakes, has experienced an increasing pace of warming since 1900.

Generally, a changing climate will exacerbate a range of risks to the Great Lakes, including changes in the range and distribution of certain fish species, increased populations of invasive species, more harmful algal blooms and declining beach health (National Climate Assessment, 2014).


Interactive Tools

You can use the following tools to learn more about temperature and precipitation, informing your assessment of your facility’s risks and impacts.

  • Climate Wizard (TNC), an interactive tool, allows users to explore future climate scenarios—such as a change in temperature and precipitation under different future carbon emissions—for specific regions. This information can be used to inform a community’s planning goals, resource management and investment decisions.


  • Summary Reports: Binational Climate Impacts and Outlook Reports (National Integrated Drought Information System)
    A two-page downloadable climate report released quarterly for regions in the U.S., including one for the Great Lakes. Includes report on surface Great Lakes water temperature and levels, precipitation and temperatures plus related impacts such as water quality, navigation and recreation, public health and infrastructure and transportation. Forecasts for water levels, temperature and precipitation and harmful algal blooms are also included.
  • Location-specific Summary Reports: Great Lakes Station Climatologies (GLISA)
    Summaries of climate information, as collected at local weather stations, for select locations in the Great Lakes region include an overview of the climate along with data and graphs. You could look her for more localized information on temperature and precipitation.
  • Map: Projected Mid-Century Temperature Changes in the Midwest: Interactive Map (U.S. Global Change Research Program – Midwest Report)
    Map showing change in average temperature and the difference in number of days above 95°F, frost-free days and cooling days (defined as days with average temperature above 65°F, which generally leads to an increase in energy use for air conditioning).

Next: Section 2: Infrastructure