South Portland is charting a course to become a more resilient city. This means we’re striving to ensure that all of our neighborhoods can anticipate, accommodate, and adapt to a changing climate. Reaching this goal will depend, in large part, on our collective ability to reimagine and reinvent our community in a way that promotes economic prosperity, social equity, enhanced quality of life, and climate resilience.

As a coastal community it’s important that we further understand the impacts of flooding from sea level rise and coastal storms. Climate models can help us to envision that future under different scenarios and by using a variety of complementary models available, we can best understand the anticipated flood impacts during calm and stormy seas.

The most current climate models we use to plan forward for the future of South Portland move away from Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps, which have traditionally been used to gauge risk, but do not account for future climate impacts. Instead, we are using a Statewide Sea Level Rise “Bathtub” model, and a new Dynamic Flood Inundation model. Each has different uses as described below.

Climate models

The FEMA Flood Insurance Rate Maps simulate past storm events for localized flood insurance purposes. FEMA maps represent the inundation (overwhelming flooding) of a 100-year storm (1 percent chance annually) and include the breaking of waves, wave run-up, and wave overtopping. The most recent FEMA map available to us in South Portland was released in 2018 and does not take into account any future sea level rise scenarios.

Statewide Sea Level Rise “Bathtub” models simulate anticipated sea level rise on a day without storms. This model was developed in 2017, updated in 2020, and provides six projections for Maine under low (1.2 feet), intermediate-low (1.6 feet), intermediate (3.9 feet), intermediate-high (6.1 feet), high (8.8 feet), and extreme (10.9 feet) sea level rise scenarios reflecting greenhouse gas emissions for the year 2100. A ‘Bathtub’ model uses LiDAR elevation data and is overlaid on top of the Highest Astronomical Tide (HAT, which is equivalent to a 12-foot high tide) and reflects only calm seas.

The Dynamic Flood Inundation Model is a new model being developed by the Army Corps of Engineers along with other partners under the umbrella of “Maine Silver Jackets” and simulates inundation from storm events (for example 10-year, 25-year, and 100-year storms) overlaid onto multiple sea level rise scenarios. The model accounts for tides, storm surge, wave formation and diffraction, reflection, and breaking, and wind and wave set-up which can increase water levels at the shoreline.

The model aligns with South Portland’s “One Climate Future” and the state of Maine’s “Maine Won’t Wait” recommendations ‘to manage’ for 1.5 feet of sea level rise by 2050 and 4.0 feet by 2100, as well as ‘to prepare’ for 3.0 feet of sea level rise by 2050 and 8.8 feet by 2100. This model also demonstrates the potential for inundation by taking into account precipitation from coastal storms and can show both where flooding may occur and how deep water levels may be. Learn more about the Maine Silver Jackets at www.iwr.usace.army.mil/Silver-Jackets/State-Teams/Maine/.

Join South Portland Sustainability and the Gulf of Maine Research Institute (GMRI) for Coastal Meet-Ups throughout the city this summer. The FEMA and “Bathtub” models are available at https://gmri.org and can help us understand how potential flooding will impact the places we all care about and rely upon. The city can’t plan for these events alone. The places we prioritize and the ways we plan for these impacts will rely on your input. Together with GMRI and their Community Science Program (https://investigate.gmri.org/project/coastal_flooding/), we can inspire, prioritize, and invest in equitable actions that strengthen our community through active observation and input.

The flooded entrance to Willard Beach. Courtesy photo/Gulf of Maine Research Institute

Reach out and join sustainability and GMRI staff for one of our Coastal Meet-Ups throughout the summer. The events are free to residents and we strongly encourage registration at www.gmri.org/events:

Wednesday, July 19 at 8 a.m., Pleasantdale Greenbelt (departing from the former Sea Dog Brewing parking lot).

Tuesday, Aug. 1 at noon, Coastal Cruise (departing from Portland Harbor; final event details, TBD)

Monday, Aug. 7 at 5 p.m., Willard Beach (departing Willard Beach snack shack/main entrance; parking is available at the Willow Street lot or on surrounding streets).

Tuesday, Aug. 29 at 5 p.m., Mill Creek Greenbelt (departing from the Hannaford parking lot; corner nearest to the Greenbelt/Mill Creek crosswalk).

The Coastal Meet-Ups are made possible through a Climate Action Grant from the Governor’s Office of Policy Innovation and Future Community Resilience Project program.

Our Sustainable City is a recurring column in the Sentry intended to provide residents with news and information about sustainability initiatives in South Portland. Follow the Sustainability Office on Instagram @soposustainability.

Steve Genovese is an AmeriCorps/Greater Portland Council of Governments Resilience Corps fellow serving in the South Portland Sustainability Office through September 2023. He can be reached at sgenovese@southportland.org.