The Risks of Sea Level Rise in Cape Cod, Massachusetts

By Brianna Nece

Climate change has become a growing phenomenon worldwide. Its effects can be lasting when higher average temperatures cause the sea level to rise as a result. Cape Cod National Seashore is starting to experience change within its beloved shoreline as a result of sea level rise. Cape Cod has already been experiencing a shift with a series of tropical cyclones, or more specifically, nor’easters, beating the coast, eroding dunes, and damaging parking in 2018. In a 2022 interagency report, the National Oceanic and Atmospheric Administration (NOAA) estimated an increase of 10 to 14 inches in sea level over the next 30 years along the east coast of the United States. The report pinpointed that expected flooding would occur 10 times as often as it does today.  Low-lying coasts such as Cape Cod would be a region of concern based on the estimate of more intense flooding. The peril from sea level rise and accelerated erosion leaves Cape Cod’s sandy cliffs and their foundation vulnerable. The active coastal erosion that rises affects the exposed glacial deposits on sea cliffs, leading to upland loss. However, active erosion is not the only contributing factor. A higher contributing factor is passive submergence. Cape Cod loses approximately 33 acres of uplands each year, with 73 percent due to passive submergence and 27 percent due to active erosion. Sea level rise not only affects the coast, but it can also impact groundwater. 

One of the most important sources of freshwater on Cape Cod is groundwater. Massachusetts water infrastructure is predominantly municipally owned, but some entities are state-owned. Water is typically carried through a piping system into a water treatment plant, where treated water is allocated into local dispersion pipes. Sewer infrastructure is also municipally or regionally owned, but another noteworthy aspect is privately owned septic systems. 85 percent of residents in Cape Cod utilize septic tanks. These septic tanks require onsite treatment and soil percolation of the water for filtration. For residential wastewater, the wastewater is taken through the piping system to a treatment plant through the sewers. These systems that are currently in place are at risk due to sea level rise. Surface water that remains in the floodplain is at risk of being inundated with saltwater during storm events and high tides. There is also the risk of saltwater intrusion in freshwater aquifers. These situations also pose a potential risk of flooding within water and sewer infrastructures, as well as corrosion in pipes. The infiltration and inflow that can occur as a result of groundwater increasing and entering into faulty pipes can also pose a threat. An overflowing sewer can risk entering nearby streams, posing a contamination threat. A contamination risk in drinking water is important to note in the case of failed septic tanks. When there is flooding, soils become more saturated, reducing their ability to retain additional water, affecting the filtration system in septic tanks. Despite the contamination risk, plans are being put in place to address these issues, such as along the Cape Cod National Seashore. 

Cape Cod’s federal and municipal leaders have been operating hastily to find answers to redirect their climate strategy and enforce more proactive measures. They came face to face with the reality that rising sea level means more coastal flooding in areas beyond those already affected. One of the first steps was for the U.S. Department of Energy’s National Renewable Energy Laboratory to conduct a pilot study of Cape Cod National Seashore. They took the necessary precautions to examine vulnerabilities within the transport, infrastructure, and waterways. The department constructing these examinations would help determine the probability of recurrence and deliver strategies towards reducing the potential risks. This report was completed in 2020, allowing a new system that prioritized decisions from local and federal officials structured towards resilience. Other research was also started in 2018 with Western Carolina University to understand the effect of transportation assets at the National Seashore. The researchers examined the Coastal Hazards and Sea-Level Rise Asset Vulnerability Assessment Protocol for forecasting how the infrastructure will perform in 35 years, anticipating 2050. This report also contained an examination of 127 transportation assets and 225 structures along the National Seashore. In 2022, the report was finalized, and 17 percent of assets were found to have moderate or high vulnerability to increased coastal threats. 

With the threat of 12 to 15 feet of erosion each year, park management also began reconstruction. They installed a new bathhouse for the facility at the most distant rear of the parking area back in August of 2022. This change arrived as part of numerous others to address sea level rise; for example, the Province Lands Road realignment and Herring Cove Beach North Parking Lot started relocation in 2019. Other restoration projects include the Herring River in Wellfeet, which was a wetland spot with invasive species. The project was initiated with the removal of a dike and the construction of a new bridge. This allowed for a fresh flow of seawater, permitting restoration to the salt marsh that was once present. Salt marshes are noted for their significant role in carbon storage. They reduce approximately 4,018,572 grams of carbon dioxide per year, which is beneficial against climate change. The additional benefit is that salt marshes can act as a buffer to reduce flooding through their ability to stabilize the sea floor with their root system. In addition to these environmental projects, water infrastructure has needs for managing seawater threats. 

Water infrastructure has several methods available for addressing sea level rise. When it comes to water contamination, desalination is an option; however, it would increase the cost of water. There could also be intrusion barriers set in place, or locate a new area where the water source is not contaminated to draw from. Another crucial aspect is that piping must be kept in good condition, given that seawater can corrode pipes. These decisions are left to each municipal group when the time comes. On behalf of the property owners, septic tanks require a safe distance from groundwater within the state of Massachusetts. This requirement is based on history, but it does not account for the changing climate and rising groundwater levels. Each individual has the opportunity to stand up against the risks associated with our changing environment. 

It is essential to note how individuals can step up and make a difference within their communities to address the threat of sea level rise. Each family or individual needs to take a first step to define and understand their risk tolerance. Next, there is time required to consider how the infrastructure of your home may be at risk, for instance, low-lying infrastructure that could be at risk of flooding. After taking these steps, you can start choosing actions of mitigation and adaptation. For mitigation, you can reduce your greenhouse gas emissions by using solar power or walking to work. In regard to adaptation, you can construct flood-reducing solutions through a new drainage system or nature-based solutions. Lastly, you can get involved within your community by participating in local assemblies and providing feedback to decision-makers. We all desire to protect our homes, and it is our choice to decide how we make a difference. Sea level rise will continue to be a threat in our future, but we can go forward with a better understanding and outlook. We are not alone in the fight against climate change, and together, we can make a difference.

Citations

1. Chalek, Melissa."Maintenance of Water and Sewer Infrastructure in Response to Sea Level Rise in Massachusetts" (2020). Marine Affairs Institute Staff Publications. 2. https://docs.rwu.edu/law_ma_sp/2

2. Giese, Graham S. (PDF) Potential Impacts of Sea-Level Rise in Massachusetts. https://www.researchgate.net/publication/237420365_Potential_Impacts_of_Sea-Level_Rise_in_Massachusetts. 

3. U.S. National Park Service.“Building climate resilience”. National Parks Service. 

   https://www.nps.gov/articles/000/building-climate-resilience.htm.

4. Shiffer, Nadya Vinogradova.“What can we do?: Sea level 101”. U.S. Sea Level Change. (2024, November 7). https://earth.gov/sealevel/us/sea-level-101/what-can-we-do/