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Written on: September 24th, 2025 in Natural Resources, Wetland Research
By Alison Rogerson, DNREC’s Wetland Monitoring and Assessment Program
Introducing Tidal Freshwater
Most people are familiar with tidal wetlands that line the Delaware Bay coast and the Inland Bays. Likewise, most of us can recognize a freshwater wetland along a stream or in a forest. But what about tidal freshwater wetlands? That’s not a typo. Tidal freshwater wetlands are a small, lesser known but unique and valuable type of wetland.
Where Are They?
Tidal fresh wetlands are both tidal and freshwater, the best of both worlds. They occur in coastal systems, primarily up rivers where fresh water and saltwater meet. You can find them at the uppermost portion of the estuarine, or salt, zone where the inflow of salt water is diluted by upstream freshwater flowing out. Salinity in these areas range from 0.5-2.0 parts per thousand (ppt). For reference, salinity in coastal wetlands is typically around 15-20 ppt.
How Many Are There?
Wetlands of this type exist from New York to North Carolina. In Delaware, there are an estimated 13,000 acres total as of 2017 which made up about 8% of our statewide wetland total. So they are a small but interesting wetland class. You can find them up every major coastal river such as the Saint Jones, Murderkill, Leipsic, and Smyrna Rivers. Further up the Delaware River, tidal freshwater wetlands become more common along major tributaries such as the Appoquinimink, Blackbird and Christina Rivers.
Why Are They Important or Special?
Tidal freshwater wetlands offer a rich and diverse plant community. Some typical species you’ll find includes wild rice, arrow arum, water hemp, pickerelweed and spatterdock, to name a few. They provide flood and storm protection and are beautiful and scenic to kayak through. Tidal freshwater wetlands also serve as great habitat for wildlife such as muskrats, turtles, wading birds, fish, and wood ducks.
What Threatens Them?
Tidal freshwater wetlands are threatened naturally and by human actions. As sea levels rise and saltwater lines advance higher and higher upstream, water and salinity levels increase to the point where plants can no longer survive. In Delaware, and other states, many freshwater streams were historically dammed to create freshwater lakes, usually for lumber mills. This artificial barrier created a hard stop where tidal waters coming upstream cannot mix with freshwater outflows freely. Over time, tidal fresh wetlands are feeling the ‘pinch’ between rising saltwaters and dam structures.
What Can Be Done?
Human impacts in tidal fresh wetlands should be permitted by state and federal offices, which helps to avoid and minimize permanent degradation. Always check with regulatory offices if you plan to construct or make changes in these areas – good contacts to have are the DNREC Wetlands and Waterways Section and the U.S. Army Corp of Engineers.
Landowners can check our Delaware Wetland Toolbox mapper to see if they are near tidal freshwater wetlands. Small steps can make a big difference over time such as removing invasive species such as Phragmites, purple loosestrife and reed canary grass. Replacing with native wetland plants improves habitat quality. Reducing pollution from lawn fertilizers, herbicides, and excess road salt helps improve wetland health.
On a state level, dam removal is an ongoing and long-term process. Dam removal is complex but offers many benefits for migrating fish species, water quality, reduced flooding as well as for tidal freshwater wetlands. Landowners can become informed and support DNREC and partner non-profit organization efforts to remove dams.
Written on: September 24th, 2025 in Education and Outreach, Natural Resources
By Kathryn Lienhard, Delaware Sea Grant Did you know that in 2022, more than 10% of the electricity generated in the U.S. came from wind energy? Humans have harnessed the power of the wind for thousands of years – most iconically, through traditional windmills – while modern wind turbines continue to advance in design and […]
Written on: September 24th, 2025 in Education and Outreach, Wetland Animals
By Olivia Allread, DNREC’s Wetland Monitoring and Assessment Program Anything new certainly can be intimidating. Sports, art mediums, cooking, recreational activities, you name it, they all have their own culture and lingo that some spend a lifetime mastering. Particularly in the natural resource world, certain topics or hobbies can sometimes come off as an exclusive […]
Written on: July 22nd, 2025 in Education and Outreach, Wetland Research
By Olivia Allread, DNREC’s Wetland Monitoring and Assessment Program Many millions of years before us Homo sapiens appeared, there lived a vast array of plants and animals in extensive environmental systems we no longer see today. With Earth having formed 4.6 billion years ago, there are certainly a lot of eras between the cloud of […]
Written on: July 22nd, 2025 in Natural Resources
By Alison Stouffer, DNREC’s Wetland Monitoring and Assessment Program Congratulations folks! You have made it to the fifth, and final, installment of the cross-country wetland road trip. I would be lying if I said this wasn’t a bittersweet moment. I am excited to explore what the Northeast United States has to offer, but sad to […]
Written on: July 22nd, 2025 in Natural Resources, Wetland Restoration
By Kristen Travers, Delaware Nature Society We’re all uncomfortably aware of how hot this summer has been. On a recent 90+ degree afternoon, while walking with a group of people, the first request was simple: “Let’s head to the stream in the shade.” As we stepped under the tree canopy along the streambank, the temperature […]
Written on: May 21st, 2025 in Education and Outreach
By Maddie Fox, Delaware Center for the Inland Bays The Delaware Center for the Inland Bays is a private nonprofit organization and one of 28 National Estuary Programs in the nation. Its creation was the culmination of 20 years of public participation and investigation into the declining water quality of the Inland Bays and the […]
Written on: May 21st, 2025 in Education and Outreach
By Olivia Allread, DNREC’s Wetland Monitoring and Assessment Program We know. This one sounds a little crazy. And by no means are we saying to throw on some boots and go out into the waist-deep mud to get yourself an afternoon snack. But, to add to all the other ways wetlands are wonderous, we wanted […]
Written on: May 21st, 2025 in Natural Resources
By Alison Stouffer, DNREC’s Wetland Monitoring and Assessment Program It’s been a few months since our last cross country road trip. With winter in the rear-view mirror, I am excited to come out of hibernation and explore the wetlands of the Southeast United States! Need a refresher on where we have been thus far? Be […]
Written on: March 19th, 2025 in Education and Outreach
By Olivia Allread, DNREC’s Wetland Monitoring and Assessment Program Nature has been engrained into storytelling basically since the beginning of time. In most cultures throughout history, the natural world has been featured in stories and books in many ways – a place of mystery, a pathway of self-discovery, foundations of peace and rest, even a […]
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