Portland’s Projected Coastal Flood Risk Interactive Web Map

This webmap was produced to provide information to community members about projected flood vulnerability and create an interactive display of the extents of potential coastal flooding in Portland, which will form the basis for a new draft Coastal Flood Resilience Overlay Zone (CFROZ).  As proposed, the CFROZ would establish new standards for flood-resilient development in Portland’s coastal areas. By incorporating projected sea-level rise and impacts of climate change, this map supplements current FEMA guidance to provide a more accurate picture of future conditions and risks.

This webmap takes into account hydrodynamic modeling around future sea level rise, tides, storm surge, and wind. Model assumptions were based on recommendations from the State of Maine’s Climate Action Plan " Maine Won’t Wait " and Portland’s " One Climate Future"  planning efforts: For more information about the City of Portland's Hydrodynamic Model click here.

• Tide Level: Mean Higher-High Water (MHHW), which represents the average of the higher high-water height of each tidal day (highest of the two high tides per day).
• Time Horizon: 2100
• Sea-Level Rise (SLR): 3.9ft , based on the State of Maine’s “Commit to Manage” scenario of 3.9 feet of SLR by 2100.
• Storm Scenario: 100-year storm, or a storm event that has a 1% chance of occurring in any given year. In Portland, this is based on Portland’s historic analogues (Blizzard of 1978). 100-year storms will continue to increase in frequency and intensity due to climate change.
• Wave Action: This component is not included in the model. This means that projected flood depth does not reflect the additional height of waves that ride on top of the water’s surface. This is represented as the stillwater level.
• Precipitation & Riverine Flooding: This component is not included in the model. This means that the map does not show freshwater flooding from rainfall or rivers.

Properties that fall partially or fully within the flood extent (shown in blue in the map) are projected to be at risk of flooding from future coastal storms. Under the City of Portland's draft approach to climate resilience zoning, these properties would be subject to the requirements of a new Coastal Flood Resilience Overlay Zone. View our proposed approach slides to learn more about how these new regulations would apply in practice.

The map depicted above was generated using the best available data, the most current scientific and engineering methods, and the best resilience practices. As Portland's climate changes, there will be larger and more frequent storms and floods that occur, the data and modeling will continually be updated to adapt to those changes over time.