Yarmouth

Contour lines can help visualize this steep topography. Here, orange lines represent elevations between 0 and 10-feet above sea level (in 2-foot increments).

The current highest astronomical tide (HAT) is displayed in red. HAT is the highest tide that can occur under average weather conditions, and is about 1.9 feet higher than Mean High Water in Casco Bay (the average height of daily high water). It provides a useful baseline for assessing potential sea level rise.

The State of Maine estimated sea level rise scenarios on top of the HAT. The State asks communities to commit to managing 1.5 ft of sea level rise by 2050 and 4.0 ft by 2100 (relative to a year-2000 baseline).

The map at right shows the area expected to be inundated with 1.5 feet of sea level rise. Note that extreme storm surges (the rise in water level from storm winds piling water up at the coast) can reach around 3-4 feet above sea level.

The amount that sea level will rise depends in part on what we do to curb greenhouse gas emissions, communities should account for multiple future sea level rise scenarios. In this visualization, 3.9 feet of sea level rise encroaches farther inland. The State asks that communities be prepared to manage for this level of water, especially for high priority infrastructure, ecosystems and when people are at risk.

The Federal Emergency Management Agency (FEMA) maps the area likely to be flooded by severe storms that have a 1% chance of occurring within a given year, under current conditions. Over thirty years, there is a 26% chance that a storm of this severity will occur at least once, so it's important to plan for.

Together, these predictions (FEMA "100-year" flood risk and HAT + 3.9 feet of sea level rise) provide a look into how flooding could impact our coastlines, habitat, infrastructure, and people within this century. FEMA does not factor climate projections into their flooding maps, so combining with sea level rise maps show a more complete picture of impacts.

Beaches and sand dunes are important coastal features subject to erosion. Here, an area of sand dune is delineated by the red shaded polygon, while water overtopping potential is indicated by the colored circles (yellow and red indicate that the base flood elevation, determined by FEMA, is above the relevant point; green indicates it is below). Retreat or expansion of beach is indicated by the colored lines (yellow, orange, and red indicate retreat, while green indicates advancement).

Some organisms, like molluscan shellfish (habitat of which is mapped at right), are important culturally as well as economically and environmentally. 

Various bird species require appropriate tidal habitats; rising sea levels and increased flooding may eliminate some of this habitat. Highlighted here are tidal wading bird habitats and seabird nesting islands.

While all habitat is valuable, Yarmouth has areas, shown in green, home to particularly vulnerable wildlife. Relevant species include roseate turn and saltmarsh sparrow. 

Because habitat can be disrupted by inland or coastal flooding, it may be important to provide buffers around habitat areas, like that of the saltmarsh sparrow. This provides the opportunity for plants and animals to shift into new locations without the threat of encroaching development. 

Some spaces within the Town's border are already protected for conservation or open space, and are displayed here. 

The Nature Conservancy developed an analysis of culverts at risk of overtopping in a flood. One culvert in Yarmouth is assessed as at high risk for overtopping. This culvert should be examined and potentially improved. 

Protective coastal structures like rip-rap and bulkheads are also at risk of overtopping during flooding events, as visualized here (yellow and red indicate that the base flood elevation, determined by FEMA, is above the relevant point; green indicates it is below). Several areas of Yarmouth coastline rely on rip-rap or other structures for stability; explore the map to view areas of potential concern.

Also at risk are elements of the area's transportation network. Shown here are roads and transportation routes, as well as the previously displayed flood hazard and sea level rise layers. 

Residents and emergency services should be aware of areas and road segments where access might become limited with flooding; this could result in safety hazards as well as travel impediments to private and public transit. These road segments are highlighted in yellow. 

Some buildings in Yarmouth intersect with these estimated flooding areas as well. These are highlighted in red on the map. These should also be assessed for safety, stability, and resilience in the event of flooding, storm surge, or sea level rise. 

As may be expected, low-lying island areas appear vulnerable.

Other coastal areas appear vulnerable as well.

The inlet along Yarmouth's northern border with Freeport is saltmarsh sparrow habitat, but much of it is not conserved. Because of potential marsh migration and development pressures, more of this land could be protected.

Dams along the Royal River are identified as potentially at risk and have been identified as impacting fish habitat.

Buildings near I-295's crossing over the Royal River are threatened by future flooding, and a nearby culvert identified as at high risk by the Nature Conservancy.

On Cousins Island, rip-rap near the Wyman Energy Center is at risk of overtopping by waves (yellow and red indicate that the base flood elevation, determined by FEMA, is above the relevant point; green indicates it is below). A nearby building is also susceptible to future flooding. Planning for future use of the power plant should consider these risks.