Identifying Opportunities for Climate Adaptation in the Delaware Estuary

Rachel M. Gregg
Posted on: 10/28/2010 - Updated on: 11/15/2021

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Rachel Gregg

Project Summary

The Delaware Estuary has a nearly continuous fringe of diverse types of tidal marshes, which serve as critical habitat for fish and wildlife and provide important services for residents in the surrounding area. Much of this habitat is presently stressed by human alterations and activities and climate change impacts appear to be exacerbating these issues. The Partnership for the Delaware Estuary (PDE), through a grant from the U.S. Environmental Protection Agency’s (EPA) Climate Ready Estuaries Program, assessed the climate vulnerabilities of tidal wetlands and two other key resources (drinking water and bivalve shellfish), identified monitoring and management needs, and created an adaptation plan. Lessons learned from this pilot project were used to inform the public and managers on how to get the best environmental return on investments designed to sustain vital resources.


The Delaware Estuary, spanning Delaware, Pennsylvania, and New Jersey, provides critical habitat for fish and wildlife, and drinking water, recreation, and food for residents. In addition, the estuary hosts the largest freshwater port in the world and five of the largest refineries on the east coast of the United States. The PDE was selected as one of the six pilot projects under the EPA’s Climate Ready Estuaries Program, receiving grants in 2008 and 2009 to support these efforts. PDE had many collaborators on this project, including the Academy of Natural Sciences, Delaware River Basin Commission, and U.S. Geological Survey. A Climate Adaptation Work Group was also set up to oversee technical elements. PDE worked with partners to examine three case studies focused on human impacts (drinking water), habitat (tidal wetlands), and living resources (shellfish) in order to assess the resources’ vulnerability to climate change. Impacts of particular concern for the area are sea level rise, salinity rise, increases in temperature, altered rainfall, and increased storms. For each of the three resources—drinking water, tidal wetlands, and shellfish—project leads conducted an inventory of project climate change impacts, identified data gaps, and identified and prioritized management options.


Drinking water, tidal wetlands, and shellfish were selected as case study topics because of their ecological and societal importance to the region:

  1. The estuary and surrounding watersheds provide potable drinking water for over 16 million people in the region. The availability of clean drinking water in the face of climate change impacts is threatened by increased salinity because many of the water intakes are from the tidal freshwater area; compounding factors include population growth, development, and alterations to freshwater flow. Project leads investigated potential vulnerabilities to drinking water supplies in the area.
  2. Tidal wetlands play an important role throughout the estuary as habitat and regulators of water quality and flooding events. This habitat is presently degraded and is further threatened by sea level rise, salinity, temperature, sedimentation, freshwater input, and flooding. This project quantified the value of the ecosystem services that tidal marshes provide.
  3. Bivalve shellfish are at risk in the estuary and its watershed. Scientists researched and modeled vulnerabilities to different both freshwater and marine species and compared potential adaptation options. Shellfish are commercially and ecologically viable in the region and are threatened by increased salinity, decreased water quality, warmer temperatures, disease, and non-native and invasive species introductions, among other factors.

Example adaptation recommendations included:

  • Protecting vulnerable drinking water infrastructure;
  • Developing and funding a climate monitoring program;
  • Identifying priority tidal wetland areas for restoration and protection;
  • Educating the  management community about key Delaware Estuary resources; and
  • Considering policy changes needed to facilitate climate change adaptation.

Outcomes and Conclusions

The final report was released in June 2010 and includes results from the assessments and adaptation strategy recommendations. This project influenced other PDE projects and they now consistently work to incorporate climate change into their programing through workshops and community outreach. For example, PDE developed Weathering Change, a resource to engage community leaders on the use of nature-based solutions as a means of community protection and water quality provisioning. As part of the development of the 2019 Comprehensive Conservation and Management Plan (CCMP), PDE conducted a vulnerability assessment to analyze how climate change could impact CCMP strategies. Climate stressors such as increasing temperatures, drought, storms, and sea level rise were ranked based on the consequences of risks, the likelihood of risks occurring, and the spatial extent and time horizon of likely impacts. The plan emphasizes the need for increased community resilience to climate change impacts and access to clean and healthy water resources.


Gregg, R. M. (2021). Identifying Opportunities for Climate Adaptation in the Delaware Estuary [Case study on a project of the Partnership for the Delaware Estuary]. Version 2.0. Product of EcoAdapt’s State of Adaptation Program. Retrieved from CAKE: (Last updated October 2021)

Project Contacts

Affiliated Organizations

The Partnership for the Delaware Estuary is a nonprofit organization established in 1996 to take a leadership role in protecting and enhancing the Delaware Estuary, where fresh water from the Delaware River mixes with salt water from the Atlantic Ocean. It is one of 28 Congressionally designated National Estuary Programs throughout the coastal United States working to improve the environmental health of the nation's estuaries.

The Environmental Protection Agency is an independent executive agency of the United States federal government tasked with environmental protection matters. The Environmental Protection Agency has ten Regional offices, each of which is responsible for the execution of the Agency's programs within several states and territories.

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