Climate Change

Sea Level

Temperature and Precipitation Sea Level

Sea Level Status Rating:

Fair

but getting worse

Here’s Why:

Sea level is rising rapidly, driven in part by climate change, resulting in more frequent flooding in our coastal communities and negatively impacting coastal habitat. Urgent measures are needed to reduce greenhouse gas and enhance community resilience in the face of this growing threat.

Did you know that the ocean is slowly inching up our shores?

Sea levels don’t just rise independently – they’re an indicator of climate change. As temperatures rise, so do sea levels due to melting polar ice and thermal expansion (where the volume of the ocean water increases due to rising temperature). And there are few places where it is more apparent than in the Delaware River Basin. The Delmarva Peninsula also faces compounding impacts of relative sea level rise resulting from land subsidence, the sinking of the land surface resulting from present-dat groundwater withdrawals, and ongoing residual effects of glacial retreat, a concept known as isostatic rebound. Sea levels at the mouth of the Delaware Bay have risen about 7 inches over the last 30 years. This may not seem like much, but this perceived minor shift has significant implications. The tidal stretch of the Delaware River (130 miles from the Bay to the head of tide in Trenton, NJ) rises and falls twice a day. Higher sea level means higher tides and more frequent and severe flooding in low-lying areas, cities, and towns. Rising sea levels can make freshwater salty, which is a concern for drinking water systems and wildlife habitats. With predictions suggesting that the sea level will rise another foot or more by 2050, urgent and proactive measures are needed. These include reducing greenhouse gas emissions and implementing strategies to increase community, habitat, and infrastructure resilience.

Rising sea levels pose a major threat to coastal communities and wetland habitats. Upstream communities along the tidal river are at risk as well. As the tide rises downstream at the Bay, it pushes saltwater further upriver, turning what was once fresh water into a salty mix. This presents a health concern for the 17 million people who rely on the river for drinking water.

The threat of saltwater isn’t restricted to the river. Saltwater intrusion occurs when saltwater seeps into freshwater aquifers below the soil surface, which, again, poses a problem for freshwater ecosystems and our drinking water. Once salt mixes in freshwater stores, it’s hard to reverse.

The rising sea level also directly influences the frequency of high tide flooding. All too soon, we’ll face the daunting prospect of compound flooding – events where multiple floods occur simultaneously or close together due to higher tides and heavier rainfall. These extreme flooding events are often coupled with intensifying storms like Hurricane Ida in 2021. The Delaware Estuary and Basin are already experiencing these unprecedented storms and their impacts. The tide does not seem to be turning in our favor, as increases in high tide levels will continue to worsen flooding during storms.

Predictions for the future aren’t promising either. The average sea level along the contiguous United States is anticipated to increase by one foot or more by the year 2050, and coastal communities across the country already feel the ramifications. To endure these changes, we need robust adaptation strategies. Measures range from creating living shorelines to building higher seawalls and elevating structures. Even so, the rise in flooding frequency tends to hit marginalized communities the hardest, as they often live in low-lying areas and have fewer resources to deal with flood-related damage and disruption.

Sea-level rise isn’t just a future possibility, it’s happening here and now. Each year, the waters edge a little closer, and the risks to our communities and wildlife rise. Without significant reductions in greenhouse gas emissions from power plants and other sources coupled with adaptation measures, severe repercussions for communities and ecosystems in the Delaware Estuary are expected. Just as we can contribute to climate change, we can also fight it. Local communities must prepare for these changes by implementing thoughtful planning, enforcing ordinances, strengthening building codes, and updating land-use plans to protect water resources and infrastructure. In areas of persistent inland flooding, strategic or managed retreat may be the best option where vulnerable human communities are relocated out of harm’s way and natural coastline areas are restored to provide additional ecosystem services. With foresight, planning, and concerted action, we can build a future where our coastal communities continue to thrive amidst the waves of change.

Things You Can Do

Reduce your carbon footprint and advocate for resiliency initiatives in your community:
Reduce energy use by replacing outdated appliances with energy-efficient models.
Protect your local wetlands by learning more about them. Sign up for a nature walk around wetlands or check out a webinar on PDE’s YouTube page.
Advocate for wetland protections and preservation.
Volunteer with local organizations that conduct wetland restoration projects.
Plant native trees and shrubs that soak up rain, provide habitat, cool the area around them, and more.

Get Involved

What is Being Done?

Philadelphia Water Department’s Climate Change Adaptation Program (CCAP) is running risk assessments for all of their critical infrastructure systems to consider climate change impacts. Philadelphia Water Department (PWD) is leading a series of comprehensive coastal flood risk assessments at their three Water Pollution Control Plants (WPCPs) and the Baxter Drinking Water Treatment Plant. All four treatment facilities are located along the tidal Delaware River and are vulnerable to coastal flooding from sea level rise and storm surge. PWD will make flood mitigation investments based on flood risks. The State of New Jersey has developed a StoryMap to communicate about the science, impacts, and effects of climate change at the state level, including a section on sea level rise.

Building Connections

How does this habitat restoration connect to the Delaware Estuary Program’s Comprehensive Conservation and Management Plan (CCMP)? CCMP STRATEGY H1.2: Restore, enhance, and manage tidal wetlands for maximum health and resilience CCMP STRATEGY H1.4: Protect, enhance, and improve non-tidal wetlands CCMP STRATEGY H2.2: Promote stewardship practices by local partners for the health and sustainability of forests for water quality This habitat restoration indicator status report is based on research compiled in the 2022 Technical Report for the Delaware Estuary and Basin (2022 TREB).

Published in December 2023 in Estuary News, the 2023 State of the Estuary Report is produced every five years.

Partnership for the DE Estuary