Flooding
Photo Credit: Tyler Brinson
Sea Level Rise
As climate change continues to warm our planet, increasing air and ocean temperatures lead to sea level rise. Two main drivers of sea level rise are:
- Melting land-based ice, particularly the glaciers of Greenland and ice sheets of Antarctica, adds additional water to our oceans.
- Warmer water physically takes up more space, called thermal expansion, which is enough to raise the sea level.
While sea level along the U.S. coastline is projected to rise by one-foot in the next 30 years, Boston and the North Shore are predicted to experience between 0.7-1.4 feet of sea level rise by 2030. By the end of the century, we could see between 4-10 feet of sea level rise depending on fossil fuel emissions.
"Scientists estimate that on average, global sea levels have risen eight inches since 1900. This rise has made low lying coastal areas, and areas along rivers near coasts, significantly more vulnerable to coastal flooding during storms and even during daily high tides.”
Sunny-day Flooding
A higher sea level increases the likelihood of “sunny–day” flooding with high tides reaching further inland. High tide nuisance flooding is occurring more frequently every year as sea levels continue to rise. Filled tidelands will be the first to flood. Increased coastal erosion, flooding of infrastructure and buildings, saltwater intrusion of drinking water supplies, and drowning of wetlands are some of the direct impacts of a higher sea level.
Storm Surge
A higher sea level also amplifies the effects of storm surge, the abnormal rise of water on the shore from a storm’s driving winds. As sea level continues to rise, coastal storm surge events will threaten areas that traditionally have not flooded, especially if the storm hits at high tide.
Seventy-nine Massachusetts cities and towns are within the MEMA coastal storm surge zone, while 21% of residential land is within a FEMA 100- or 500-year flood plain. According to the NOAA sea level rise viewer for Essex County, 17,266 people currently reside in low-lying areas, which will experience the impacts of less than 2 feet of sea level rise.
On the North Shore, over 90% of areas impacted by 2–feet of sea level rise are natural features, such as wetlands, dunes, and parks. These natural barriers protect our communities from the impacts of storms and provide important ecosystem services, such as increasing biodiversity and creating habitat for many species. Salt marshes are particularly vulnerable to the impacts of sea level rise, as human infrastructure often blocks their ability to migrate inland.
Explore NOAA’s Sea Level Rise Viewer to observe the impacts of sea level rise on your community.
More Frequent and Intense Storms
Global temperature increases that lead to sea level rise also contribute to more intense storm events, such as heavy downpours, blizzards, and hurricanes. Hot air holds more moisture, while the added heat energy in the ocean fuels more intense storms. With every 1°C (1.8° F) of warming, the air can hold 7% more moisture. The Northeast region of the U.S. has seen the greatest increase in intense rainfall events, with a 70% increase in heavy downpours from 1958-2010, according to the National Climate Assessment.
By 2050, Massachusetts’ winter and spring rainfall is projected to increase, with the number of days receiving precipitation increasing up to 42% and annual rainfall increasing up to 6 inches.
The projected increase in more frequent and intense storm events has a direct impact on inland flooding. Heavy downpours quickly saturate the soil and overwhelm municipal stormwater systems. Impervious surfaces, such as parking lots and roads, prevent absorption of water into the soil, leading to more flooding and causing chemical runoff and debris to be washed into waterways. Inland flooding damages buildings, increases exposure to pathogens in floodwater, and can disrupt emergency or evacuation routes.
Preservation in a Changing Climate
Salem Sound Coastwatch, the City of Salem, and the Salem Preservation Partners hold an annual conference in September to raise awareness of climate change impacts on historic buildings, landscapes, and neighborhoods. The discussion of adaptation strategies is just beginning.
Click here to view the recorded presentations, walking tours, and 2023 date.
