Types of Wetlands

There are many different types of wetland communities in the Carolinas; in fact, some wetland communities are nearly unique to this part of the country, like Carolina Bays and pocosins.  The North Carolina Wetland Assessment Method (NCWAM) was developed  by the North Carolina Division of Environmental Quality specifically for North Carolina and these types are generally recognized in South Carolina as well.  There ares 16 general wetland types in North and south Carolina.

Salt Marsh & Brackish Marsh

Salt Marsh and Brackish Marshes are found near the oceans and inlets of the Coastal Plain ecoregion of the Carolinas. These marshes receive regular or occasional flooding by tides, mixing with freshwater from rivers, streams, and upland runoff.    Like other types of marshes, Salt Marshes and Brackish Marshes both contain primarily herbaceous (non-woody) plant species and can occur on mineral (rocky) or organic (dirt) soils. Salt marshes experience a higher degree of salt water flooding from the ocean than Brackish Marshes, due to high tides twice a day.

Salt Marsh in Cateret County, NC (Photo by Alvin Braswell)

The Salt Marsh plant community tends to be dominated by saltmarsh cordgrass. Other plants to be found include black needle rush, large salt meadow cordgrass, sea oxeye, and American glasswort. The roots of the vegetation help trap fine-grained mineral sediments, and the root mat that develops over time is key to the long-term growth of the marsh. The patterns of growth in these marshes can often be linked to environmental factors such as land elevation and tidal flooding.

Brackish Marshes are not directly connected to ocean waters and typically have a wider range of plant species. The influx of freshwater into these wetlands carries fine-grained silt, which accumulates to produce a soft ground surface known as “pluff mud”.
Both Salt and Brackish Marshes provide critical nursery habitat for many species of fish, crabs, and shrimp. Oysters are also common in these marshes, and their filtering capabilities help improve water quality. Salt and Brackish Marshes also help protect coastal shorelines by slowing currents and trapping sediment, especially during storm events.

Estuarine Woody Wetland

Estuarine Wood Wetland (Photo by Rick Trone)

Estuarine Woody Wetlands are found along the edge of estuaries and Salt or Brackish Marshes. These wetlands are occasionally flooded with salt or brackish tide water, often due to storm surges. These storms can produce erratic tidal flooding and salinity levels in these wetlands.

Estuarine Woody Wetlands are dominated by woody vegetation (greater than 50% woody species cover), and provide habitat for trees such as loblolly pine, cedars, red maple, and sweetgum. Shrubs such as silverling, marsh elder, and wax myrtle are found in these wetlands, along with various herbaceous plants. These wetlands can vary in area from hundreds of acres to narrow fringes, depending on the land’s height and location

Tidal Freshwater Marsh

Tidal Freshwater Marsh at Lockwood Folly, NC (Photo by Michael Burchell)

Tidal Freshwater Marshes are often found in the spaces between forests and rivers. These marshes occasionally receive tidal flooding, but generally remain saturated with freshwater. These marshes occur on both mineral and organic soils, and they tend to be dominated by herbaceous plants. Tidal Freshwater Marshes are usually characterized by the presence of cattails and other plants such as sawgrass. Due to their dependence on freshwater to keep salinity levels low, Tidal Freshwater Marshes are more vulnerable to rising sea levels.

Riverine Swamp Forest

Riverine Swamp Forests are found throughout the Carolinas but are most abundant in the Coastal Plain region, and can range in size from narrow strips of land to hundreds of acres. Many Riverine Swamp Forests are found along the wettest portions of large river floodplains. These wetlands can also be formed by the presence of long-standing beaver dams.

Riverine Swamp Forest (Photo by Rick Trone)

Riverine Swamp Forests can be found on mineral or organic soils, and will experience seasonal to semi-permanent flooding. This flooding generally occurs from tides, and, to a lesser extent, groundwater and overland runoff from rain.

In the Piedmont and Blue Ridge Mountain area, the vegetation in these . is most often water-loving tree species such as Overcup Oak, Ashes, and American Elm. In the Coastal Plain region, Bald Cypress, Black Gum, and Water Tupelo are more prevalent. Shrub and herb layers in these wetlands can be sparse, especially in areas with very long periods of flooding. Lizard tail and various species of ferns and sedges can commonly occur during drier time periods or in drier areas of the swamp on hummocks or closer to the edge. Hollow trees in riverine swamp systems provide homes for animals such as bats and chimney swifts. These forests also provide nesting habitats for birds such as egrets and herons.

Seep

Seep Wetland near Middle Creek (Photo by Alvin Braswell)

Seeps are wetlands that occur anywhere in the Carolinas where groundwater reaches the surface. Seeps are defined by their unique proximity to this slow-moving groundwater.  Seeps usually occupy small areas on sloping hillsides leading down to a floodplain. The slow flow of water through a seep will saturate the soil most of the year. Seeps typically occur over an impermeable layer of clay or bedrock that will keep the soil above saturated.

Seeps feature vegetation that can change between ecoregion. In the Piedmont and Mountain ecoregions, a seep may have a forested edge that wraps around a open, herb covered interior. In the Coastal Plain ecoregion, a seep’s vegetation is depends on frequent brush fires (natural or prescribed) to remain healthy, and can range from dense to sparse shrub cover. Seeps can play host to unique vegetation, such as Eller Seep in Western North Carolina, the site of the state’s only green pitcher plant population. Salamanders are very common in seeps as well.

 

Hardwood Flat

Hardwood Flat Wetlands (Photo by NCDEQ)

Hardwood Flat wetlands are found more commonly in the coastal plain in flatter areas between streams (known as interstream flats).
Hardwood Flats are primarily forested, with broad-leaved trees that drop their leaves in in the fall (deciduous leaves). These wetlands occur on mineral soils that are seasonally wet or flooded. Common deciduous trees found in Hardwood Flats include various species of oak, such as swamp chestnut, laurel, willow, and water oaks. Other deciduous trees include those such as tulip poplar, sweet gum, American elm, red maple, and black gum.

Non-Riverine Swamp Forest

Non-Riverine Swamp Forests occur primarily on poorly drained flatland free of streams, rivers, or estuaries in certain areas of the Coastal Plain. This wetland type is fed for most of the year by groundwater discharge, overland runoff, precipitation, or a combination of the three.

While the topography of this wetland type is flat, it is typically characterized by hummocky ground that provides good water storage. This wetland type occurs on mucky mineral or organic soils that are not associated with a stream. Non-Riverine Swamp Forest is typically characterized by forest, featuring tree species such as bald cypress, black gum, Atlantic white cedar and loblolly pine.

Ridges Mountain Non-riverine swamp forest (Photo by Rick Trone)

This wetland type can be found in various sizes, but is less prevalent due to human activity. Agricultural clearing, logging, conversion to pine plantations, and ditching and draining practices have impacted completely or drastically changed these natural wetland habitats.

Pocosin

Pocosin wetlands occur in the Coastal Plain ecoregion from southeastern Virginia to South Carolina. The name “pocosin” is an Eastern Algonquin word for “swamp-on-a-hill”.

Pocosin wetland (Photo provided by NCDEQ)

Pocosins occur in large flat areas between river or stream floodplains (interstream flats) and include features like the spherical-shaped Carolina Bays. Pocosin are wet for part of the year and can be flooded with ground water. They typically have acidic and nutrient poor organic soil that has accumulated over time on top of mineral soils.

Pocosins are characterized by dense waxy shrub and woody vine vegetation. In some cases, trees like loblolly bay, swamp bay, sweet bay and pond pine are scattered throughout. Dense vegetation can quickly turn a pocosin hike into a crawling expedition. A hiker should never venture far into a pocosin without a GPS unit or compass. Pocosins also provide food for migrating birds and black bears — the latter of which being another reason to take precautions during a pocosin hike. Due to their inaccessibility to people, pocosins provide good wildlife habitat.

Pine Savanna

Pine Savannas are now rare and found scattered throughout the Coastal Plain ecoregion of the southeast, in the wide flat areas between streams and rivers (interstream flats). They have mineral soils that are poorly drained and remain wet for part of the year. They typically do not flood.

Pine Savanna (Photo by NCWAM)

Pine Savannas generally have a more open canopy and shrub layer. The canopy is composed of longleaf and pond pine trees. Scattered shrubs include gallberry, blueberry, wax-myrtle, and dangleberry. The ground layer is a diverse combination of grasses, sedges, and wild flowers.

Pine Savanna’s are home to the unusual Venus Fly Trap, a carnivorous plant that is “endemic” (unique to a region), and found naturally only within a 90-mile radius of Wilmington NC.
Pine Savannas also provide habitat for the red-cockaded woodpecker, a federally endangered species that nests in the cavities of mature longleaf pine trees. Frequent ground fires maintain the open grass and herb covered understory. Historically, lightning strikes and Native Americans would start these fires. Today, conservation land managers carefully plan and execute “prescription” fires to preserve and manage Pine Savannas.

Pine Flat

Pine Flats are primarily found in the wide interstream flats of the Coastal Plain ecoregion. Pine Flats usually occur in mineral soils that are saturated part of the year. The tree canopy is generally composed of pine, as the name suggests.

Pine Flat wetland, Little Dismal Swamp (Photo by Kristie Gianopulos)

Pine Flats, as defined by NCWAM, are not natural wetlands. These wetlands exist due to changes in the landscape caused by human activity. Pine Flats can be either a “managed” pine plantation (rows of planted pine trees) or an early “successional” forest (land that has been clear-cut) with many shrubs and saplings. Natural wetlands with similar hydrology found on interstream flats (e.g. Hardwood Flats and Pine Savannahs) will develop into wet Pine Flats when logged.

Basin Wetlands

Basin Wetlands are natural depressions in the earth that are surrounded by uplands, or occur on the edges of small lakes or ponds. Basin Wetlands are found in the Piedmont and Coastal Plain ecoregions of the Carolinas. They tend to be wet for only part of the year, and can dry up during the warmer months.

Basin wetland, Croatan National Forest (Photo by Rick Trone)

Basin Wetlands are fed by groundwater, overland runoff, and rain. These wetlands generally have sandy to fine clay based soils. Some Basin Wetlands have an underground clay layer that acts as a natural seal, and can hold water above ground for months at a time.
Basin Wetlands can vary enormously in size, from small pools (often referred to as “vernal pools”) to some elliptically shaped “Carolina Bays”.

Basin Wetlands provide important breeding habitat for amphibians, such as frogs and salamanders, because these wetlands often do not contain fish that eat these amphibians. Because Basin Wetlands exist in many forms with variable hydrology, their vegetation can vary widely, ranging from tree species to herbaceous sedges and floating wetland plants (e.g. lilly pads and duckweed). to .

Bog

A bog can be found on either floodplains or lowlands in the western part of the state, typically within the Blue Ridge Mountains and western Piedmont foothills. Bogs are formed by a poorly understood combination of groundwater seepage and blocked overland runoff. This kind of wetland is moist but not flooded, and is found over organic or mineral acidic soils.

Tater Bog (Photo by Ed Schwartzman)

Bogs exist in many forms, from forested to tree-less, from mossy to near bare earth. Beaver dams that can flood a bog, turning it into a Non-tidal Freshwater Marsh.

In general, a bog’s vegetation exists in one of two forms: 1) small, grass-like plants with or without tree cover, and 2) tree cover with vegetation clustering in areas exposed to sunlight. Some of the plant species found in bogs include Sphagnum moss, Cinnamon Fern, and various kinds of pitcher plants. Shrubs include possumhaw, northern wild raisin, tag alder, swamp rose. Trees include red maple, river birch, white pine, hemlock and occasionally red spruce.

Bogs provide important habitat for rare animal and plant species, such as Bog Turtle, Four-Toed Salamander, Alder Flycatcher, and various types of orchids, pitcher plants and azaleas. The range of this wetland is limited by the amount of flat, wet land found in the Blue Ridge and foothills.

Non-Tidal Freshwater Marsh

Non-Tidal Freshwater Marshes are found throughout the Carolinas in the floodplains of rivers and streams. They also can be found along the edge of large lakes. These marshes can vary greatly in size, depending on their location in the landscape. Like other types of marshes, Non-tidal Freshwater Marsh vegetation is dominated with herbaceous species and can occur on mineral or organic soils. This marsh type is typically flooded with freshwater most of the year, and are generally not affected by tides, as the name suggests.

Non-tidal Freshwater Marsh (Photo by NCDEQ)

Non-Tidal Freshwater Marshes can also develop in areas affected by man-made disturbances, like a utility corridor built on a once forested floodplain, water impounded by road ways, or along the edge of a man-made lake. A beaver dam can also raise water levels and turn a forested floodplain into this type of wetland.

Floodplain Pool

As their name suggests, Floodplain Pools are found throughout the Carolinas in the floodplains of creeks and rivers. These wetlands often occur in old stream or river channels (also known as oxbows), often at the base of a slope. They are generally small in size, typically occur on mineral soils, and remain flooded for part or most of the year.

Floodplain Pool wetland (Photo by NCDEQ)

Floodplain Pools are fed by rain, groundwater, and occasional flooding from a nearby river or stream. Trees commonly grow around the edge of the pool rather than inside the pool, where a variety of ferns, sedges, and other herbaceous plants can be found.
Like Basin Wetlands, Floodplain Pools tend to dry out in the summer months and provide important breeding habitat for amphibians.

Headwater Forest

Headwater Forest wetlands are found throughout the state, from the Coastal Plain to the Mountains. They are located above and drain to small streams, which function as natural drainage features in the landscape.

Headwater Forest wetlands (Photo by NCDEQ)

Groundwater and overland runoff from higher elevations provides slow surface water flow for headwater wetlands. Hence, these wetlands can be very important to protecting water quality in the entire watershed. Headwater Forests generally do not receive overbank flooding from streams like both Bottomland Hardwood and Riverine Swamp Forest wetland types do. They are saturated during significant portions of the year, but are still relatively dry when compared to other wetland types associated with floodplains.
Headwater Forests are usually fairly flat and can temporarily hold water in slow flowing channels or small depressions. Headwater forests are valuable since they filter pollutants from stormwater runoff that enters them and removes these pollutants before they enter streams. Headwater forests also provide good amphibian habitat for animals such as salamanders.

Bottomland Hardwood Forest

Bottomland Hardwood Forests are found throughout the Carolinas in the floodplains of larger streams. These wetlands can vary widely in character, depending on the size of the floodplain as well as which region of the state the forest is located.

Bottomland Hardwood Forest wetland, Parker Farm, NC (Photo by Kristie Gianopulos)

Bottomland Hardwood Forests are generally flooded for only part of the year and tend to be drier then Riverine Swamp Forests. Bottomland Hardwood Forests and are found on mineral soils. Floodwaters from rivers or streams can serve as an important source of water for these forests, especially in the coastal plain, but less so in the Piedmont and Mountains where groundwater and surface runoff are more common.

Bottomland Hardwood Forests are dominated by a variety of hardwood trees, including various oaks, red maple, ashes, sycamore, sweetgum and American elm.