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Rising Seas in the Mid-Atlantic

Written on: March 5th, 2020 in Living ShorelinesOutreachWetland Restorations

by Erin Dorset, DNREC Wetlands Monitoring & Assessment Program

Current high water conditions (mean higher high water, MHHW) and 1 and 2ft sea level rise (SLR) projections for a salt marsh in Delaware. Notice that most of the marsh is projected to be submerged with 1ft of sea level rise.

If you’re in the world of wetlands, sea level rise is a common topic of conversation. For example, here on our blog, we’ve talked about long-term monitoring efforts relating to marsh resilience in the face of rising seas and about saltwater intrusion into forested freshwater wetlands. We’ve also had a contributing author discuss effects of rising seas on trees near tidal marshes. However, sometimes we forget to stop and think about the reasons why we are experiencing sea level rise. So, let’s back up a little bit.

Why is the Mid-Atlantic a hotspot for sea level rise, and what does that mean for our coastal wetlands?

A Global Problem, A Mid-Atlantic Crisis

Sea level rise largely began with global warming, or an increase in Earth’s global temperatures. Global warming is caused by greenhouse gases absorbing and trapping solar radiation, which warms the planet more rapidly than would occur naturally. As global temperatures have risen, massive ice sheets and glaciers in Greenland and Antarctica have begun to melt rapidly, increasing sea levels. Plus, as ocean waters get warmer, they expand, further raising water levels on a global scale.

Although it is happening around the world, there are some spots that are being affected more than others. The Mid-Atlantic Coast—including Delaware—is experiencing one of the highest rates of sea level rise in the U.S, second only to the Gulf Coast.

A diagram showing the process of glacial isostatic adjustment.

Thousands of years ago, when glaciers covered much of North America, land that was just outside of the glacial footprint—such as the Mid-Atlantic region—was forced upward as the glaciers pressed down on the land they resided upon. Once the glaciers were gone, pressure was lifted, and the land that had been forced up began to slowly sink down again. That process, called glacial isostatic adjustment, is still happening in the Mid-Atlantic today. As the land sinks, or subsides, sea levels rise even more.

Worries and Hopes for Coastal Wetlands

A. gradual slope with natural lands behind allowing wetlands to move or migrate inland, B. a slope with “nick point” such as roads, development or bulkheads that prevent a wetland from moving or migrating inland (Source: Texas A&M AgriLife Extension, Climate Change Impacts on Tidal Wetlands)

Tidal wetlands have the amazing ability to gain elevation (or height) in nature. When marsh plants die, they pile up on the marsh surface and decompose slowly, while live plants help trap and keep sediments in place and out of the water. Unfortunately, sea levels are rising too quickly in the Mid-Atlantic for many wetlands to keep up. This can result in a couple of different scenarios:

  1. In some cases, marshes are lucky and have a gradual slope and natural land behind them. They can move or migrate inland as water levels climb, converting forests to wetlands as they go. 
  2. Many marshes are not so lucky, though, as roads and development often prevent them from migrating inland. Tidal wetlands will eventually drown if they are unable to move or migrate and if sea levels continue to rise. This is a huge deal, because if coastal wetlands are lost, so are their important functions, including protection from coastal storms and flooding, providing wildlife habitat, filtering pollutants, and carbon storage.

Science Lending a Helping Hand

As bleak as this outlook may sound, there is hope, too. As previously mentioned, some Mid-Atlantic wetlands might be able to keep up with sea level rise by naturally gaining enough height or elevation, while others may be able to migrate inland. In places where that is not the case, scientists and land managers are looking into other ways to save or restore tidal wetlands wherever possible and make them more hardy in the face of sea level rise. A couple of these projects include:

Beneficial use of dredge material to increase elevation of a degraded marsh in the Piney Point Tract of Assawoman Wildlife Area in Delaware.

Beneficial use of dredge material

This strategy involves using dredge material to increase elevation of struggling tidal marshes to an elevation that is optimal for plant growth, which makes them more stable. Beneficial use can also be used to rebuild marshes that have been lost completely from erosion and sea level rise. See a Delaware example!

Living shorelines

Tidal shorelines that are suffering from erosion can become stronger by using nature-based materials, such as coir logs, coir matting, and oyster shells. Look at one of the latest Delaware examples!

By incorporating the latest sea level rise projections for the Mid-Atlantic into these kinds of projects, professionals can help put our best foot forward to help coastal wetlands in our region.


Rising to Meet the Challenge; Delaware’s Communities Start a Path Forward to Improving Resiliency

Written on: March 13th, 2020 in OutreachWetland Restorations

Guest writer: Kelly Valencik, DNREC Delaware Coastal Programs Communities Seeing Shifts in Mother Nature Many communities throughout our state have already seen changes as a result of climate change- from shifting rainfall and storm patterns, to increased drought, to flooding from sea level rise. These consequences of the warming earth and ocean temperatures as a […]

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LiDAR Accuracy in Delaware’s Salt Marshes

Written on: March 6th, 2020 in Wetland Assessments

In tidal marshes, accurate representation of marsh elevation or height is critical for understanding sea-level rise, tidal inundation, and storm surge. Small changes in marsh elevation can significantly change the water movement (hydrology), plants (vegetation), and habitat. Our study aims to look at and correct a remote sensing method known as light detection and ranging (LiDAR), in order to provide accurate elevation data to scientists and coastal managers in Delaware.

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Wetland Carnivorous Plants… nothing to be afraid of

Written on: March 5th, 2020 in Outreach

Man-eating plants are a thing of sci-fi movies, they will send vines out to capture you or leap at you and consume you but back in the real-world carnivorous plants are a real thing. The world consists of more then 600 known species of carnivorous plants that use varying tactics to capture and digest their prey.

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Wetlands and their Plant Invaders

Written on: December 11th, 2019 in Outreach

You don’t have to own 20 acres of flooded fields to make a difference! There are many common wetland stressors that are not an easy fix, such as ditching and channel straightening but addressing invasive plants is a great place to start.

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Riparian Forest Buffers

Written on: December 10th, 2019 in Wetland Restorations

Riparian buffers are planted areas specifically next to waterways, such as streams, ponds, wetlands, and rivers. These areas are extremely important to keeping our waters healthy.  They do so by filtering and trapping nutrients and sediment out of waters before they enter our local waterways.

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Spartina: A Name of the Past

Written on: December 5th, 2019 in Outreach

When we think of Delaware’s coastlines, nothing comes to mind quite like the beautiful, expansive marshes full of saltmarsh cordgrass blowing in the gentle sea breeze. Our team has become especially well-acquainted with this grass, known by most as Spartina alterniflora, as we have visited hundreds of tidal wetland sites over the years.

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Sassafras Landing: A living shoreline demonstration

Written on: September 16th, 2019 in Living Shorelines

On a warm July morning not long after the official start of summer, some 2 dozen volunteers gathered at Sassafras Landing, an unimproved boat launch popular with kayakers and duck hunters inside the Delaware Division of Fish and Wildlife’s Assawoman Wildlife Area (AWA) near Frankford. Their mission: transplant nearly 5,200 plugs of native marsh grass onto what otherwise appeared to be a pristine white sand beach.

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Piedmont vs. Coastal Plain Wetlands: A tale of two regions

Written on: September 16th, 2019 in Outreach

If you spend a lot of time traveling around Delaware, you’ll notice that northern Delaware is very different from the rest of the state. That’s because Delaware is made up of two distinct geologic regions. The northernmost part of Delaware is within the Piedmont region, while the rest of Delaware lies within the Coastal Plain region.

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Confessions of Seasonal: Everlasting impressions

Written on: September 16th, 2019 in Wetland Assessments

Wetlands work is not for the faint of heart. I won’t sugar coat it for you. Its dirty. Its messy. Oftentimes pretty buggy (even though we really lucked out this year). Yep. Wetlands can be all of those things. But – they are also so much more.

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Delaware Wetland Management & Assessment Program