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New Delaware Wetland Maps Available

Written on: September 24th, 2020 in Wetland Assessments

by Alison Rogerson, Wetland Monitoring & Assessment Program

Map of Delaware’s wetlands based on 2017 imagery.

Measuring wetland health and function is a primary task for DNREC’s Wetland Monitoring and Assessment. We work on this every year, one watershed at a time. Tracking wetland acreage across the state is also vitally important to managing Delaware’s wetland. Updating statewide wetland maps is a lot of work and costly and is done every 10-15 years.

In 2017, DNREC embarked on a 10-year update of Delaware’s statewide wetland maps. These maps use a computer analysis and the best technology available to draw wetlands of all types into a GIS layer and create a census of biological wetlands. These maps are hugely important for understanding what kind of wetlands Delaware has and how they are changing over time.

After much processing and quality checks we are excited to present several new wetland layers available to the public for access. Those readers familiar with the U.S. Fish and Wildlife Service NWI Wetland Mapper should note that Delaware has been updated with the 2017 data.

Another host for accessing and downloading new wetland maps is FirstMap under Hydrology as Delaware Wetlands where there are multiple layers available:

1. 2017 Wetlands- maps all types of wetlands by two classification schemes (NWI and LLWW). This layer now also includes surface water features from the NHD layer, so streams and ditches and rivers are mapped alongside wetlands in one place.

2. Wetland Trends- this layer was created by laying the 2017 wetland map over the 2007 wetland map and noting any differences (gains, losses or changes in wetland type). Some of the losses may have been permitted or naturally occurring. Some of the changes or shifts in wetland types were caused by natural processes such as sea level rise or succession.

3. High Marsh/Low Marsh – this is a brand new layer that serves as a baseline assessment of these habitat types to help track future response to climate change and sea level rise. Low marsh habitat would typically be dominated by Spartina alterniflora. High marsh habitat is likely to be Spartina patens, Iva frutescens, or Distichlis spicata.

Example of low marsh (left) and high marsh (right) data sets.

4. Ordinary High Water Line – depicts high water line along the coast, generally following the high marsh upper boundary, and can be useful for landuse planning to estimate the upper extent of tidal influence.

Example of high water line layer along coast.

5. As a historic reference the 1992 Wetlands and 2007 Wetlands layers are still available online.

These mapping layers represent biological wetlands and do not serve as regulatory or jurisdictional boundaries. Contact Watershed Assessment Section with questions or issues accessing or using these data at (302) 739-9939. 

Stay tuned for a story map that summarizes results from the new data and highlights the updated layers offered to the public. 


Wetlands in an Urban Landscape: The Red Lion Watershed

Written on: September 17th, 2020 in Wetland Assessments

By Erin Dorset, Wetland Monitoring & Assessment Program Most of our wetland assessments throughout the years have been in central and southern Delaware, but in the summer of 2017, our Wetland Monitoring and Assessment crew went north to perform wetland condition assessments at 116 wetlands in the Red Lion watershed. From protocol updates to navigating […]

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Microplastics: A Not So Tiny Tale

Written on: September 17th, 2020 in Outreach

By Mike Mensinger, DNREC Coastal Programs Humans rely heavily on plastics in the modern era. We produce and use plastics for many things in life including, but not limited to, product packaging, plastics bags, utensils and much more. Simply look around your current area and count the number of plastic products or components surrounding you. […]

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Dinophysis acuminata: a dinoflagellate you should know

Written on: September 17th, 2020 in Outreach

Guest Student Writer: Amanda K. Pappas, Delaware State University What is a dinoflagellate? Dinoflagellates are a group of microscopic, mostly unicellular aquatic protists that are members of the plankton community. They live in fresh and marine waters, spanning the tropics to the arctic. Fossil records of dinoflagellates exist that are hundreds of millions of years […]

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It’s an Algae, It’s a Plankton, NO It’s SAV!

Written on: September 17th, 2020 in Outreach

By Michael Bott, DNREC Watershed Assessment and Management Section Delaware’s Inland Bays (Rehoboth Bay, Indian River Bay, and Little Assawoman Bay) are home to many familiar animals such as finfish, crabs, and clams. But did you know that in addition to these aquatic animals, the Inland Bays are also home to many types of aquatic […]

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Off the Rails: Studies on Delaware Clapper Rail

Written on: May 18th, 2020 in Wetland Animals

Colloquially known as marsh hens, the Clapper Rail (Rallus crepitans) is a vocal inhabitant of saltmarshes across the eastern coast of the United States and down into the Caribbean. Many of the first in-depth observations of Clapper Rail occurred in the mid-Atlantic, and in Delaware, Brooke Meanley documented much of their ecology. The northern Clapper Rail populations, including Delaware, have been declining based on extensive survey work conducted by the Saltmarsh Habitat Avian Research Program (SHARP).

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Waterway Management in Delaware

Written on: May 15th, 2020 in Beneficial Use

The Shoreline & Waterway Section (SWMS) manages 27 channels in all 3 counties of the State of Delaware. SWMS collaborates with WMAP to find creative and beneficial ways to use sediment dredged

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Delaware’s Climate Action Plan: The First State’s Future

Written on: May 13th, 2020 in Outreach

Delaware is known for its ability to tackle complex problems by bringing its residents together to work out solutions. Among this year’s problems: planning how the state will respond to climate change.

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The Amazing Oyster

Written on: May 13th, 2020 in Living ShorelinesOutreachWetland Restorations

At first glance, an oyster appears to be little more than, well, a bit of goo inside a rock. But actually, the humble oyster is an environmental warrior with an impressive bag of tricks up its sleeve, and it serves as a keystone species upon which depends the health of a marine ecosystem and the surrounding marsh.

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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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Delaware Wetland Management & Assessment Program