Grassed swale

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Grassed swale
What is a grassed swale and what does it do? A
grassed swale is a long and shallow depression,
typically much wider than deep. It is designed
to hold storm water runoff, allow the water to
soak into the ground, and filter it at the same
time.
Where can you find a grass swale? A swale may
be found alongside roads, sidewalk, streets, and
in parking lots. This swale has been
incorporated into the parking lot island. Its
purpose is to hold and filter storm water that
runs off the parking lot.
Are there other benefits to using grass swales
besides storm water control? One benefit is
cost. The cost of designing and installing a
swale is less expensive than installing curb,
gutter, and underground storm water pipes.
Another benefit is the aesthetic value of a
swale. A grass swale provides visual variety by
introducing green plants in an otherwise
continuously hardened paved area
Storm water best management practice Using a
grass swale is a storm water best management
practice (BMP).
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Pervious Pavement
What is pervious pavement and what does it
do? Pervious pavement is a special type of
pavement that allows runoff to soak into the
ground underneath the pavement instead of flowing
over it. The sandy soils of the Outer Banks are
ideal for pervious pavement because they are able
to soak up the storm water. There are many types
of pervious pavement such as brick pavers, grass
pavers, and porous asphalt
Where is pervious pavement used? Pervious
pavement materials such as gravel, stone, and
block pavers can be used for driveways, walkways,
and low use parking lots. The pervious pavement
in front of you is used in several parking spaces
and is called brick pavers.
Storm water best management practice Using
pervious pavement instead of impervious pavement
is another type of storm water best management
practice (BMP).
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Bioretention Area
What is a bioretention area and what does it
do? A bioretention area is one that uses plants
and soils to remove pollutants fromstorm water in
the immediate surroundings. A bioretention area
is designed as a shallow depression and
landscaped with a variety of native grasses,
shrubs, and trees. Sand and permeable soils are
layered beneath the vegetation, and the surface
is mulched. These layers allow the storm water
to slowly infiltrate into the ground, while at
the same time filtering out pollutants such as
sediments, nutrients (nitrogen and phosphorous),
and heavy metals.
Why are plants an important part of a bio
retention area? Plants help to filter pollutants
from stormwater and can absorb large amounts of
water. A dense vegetated area with a variety of
plants absors much more water than a simple
grassed area. Did you know that a tree will
absorb up to 50 gallons of water a day? A
bioretention area, or rain garden, is designed to
enhance its surroundings after all, it is a
garden! Native plantings add a natural quality
and they provide food and shelter for local
wildlife such as birds.
Storm water best management practice A bio
retention area, or rain garden, is a storm water
best management practice (BMPs).
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Wetland Enhancement Area
What is this large area in front of me and what
does it do? In front of you is a wetland
enhancement area, approximately 1.5 acres in
size. The purpose of the wetland enhancement
area is to improve the quality of the water that
leaves the Dare County Administrative Building
grounds.
How does a wetland enhancement area treat storm
water? Wetlands help treat storm water in two
important ways 1. Capture and slow down storm
water runoff. Several layers of vegetation,
soil, and organic material all help hold storm
water and allow it to slowly infiltrate back into
the ground. If storm water runoff is not
captured, then it may cause dangerous flooding.
2. Filter out pollutants in storm water.
Wetland vegetation and soil both help filter
storm water by capturing the pollutants before
they exit the wetland habitat. Pollutants, such
as nitrogen and phosphorus, aid in wetland plant
growth. Bacteria and other microorganisms in the
soil help to breakdown other organic compounds.
What kind of habitat is in this enhancement
area? This wetland enhancement area contains
three types of habitats that can be found here on
Roanoke Island a freshwater marsh, a bottomland
hardwood system, and a pocosin wetland.
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Freshwater Marsh
The freshwater marsh is located there. It is a
freshwater marsh because it is not connected to a
body of salt water and its primary water supply
comes from rainwater and a high water-table, both
freshwater sources. A deep layer of muck exists
in the central portion of the freshwater marsh.
This muck supports microorganisms that are the
basis of the food chain in the wetland. A
freshwater marsh is ideal habitat for waterfowl,
egrets, waterbugs, and birds.
Plant species include Cat-tail (Typha
latifolia) Rush (Juncus effuses) Sedges (Carex
spp. and Cyperus spp.) Arrow-arum (Peltandra
virginiana) Rose mallow (Hibiscus moscheutus)
Small shrubs include Buttonbush (Cephalanthus
occidentalis) Swamp rose (Rosa paulstric) Black
willow (Salix nigra)
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Bottomland Hardwood System
The bottomland hardwood system is located
there. This area will be a mixture of
bottomland hardwood and a Coastal Plain small
stream swamp. The soils within this wetland will
remain saturated nearly year round, with little
standing water, except for small depressed areas.
The small depressed areas are built to capture
and hold excess water during and after rain
events.
Large woody plant species include Bld cypress
(Taxodium distichum) Swamp tupelo (Nyssa
biflora) Swamp chestnut oak (Quercus
michaux) Yellow poplar (Liriodendron tulipifera)
Smaller shrub species include Blueberry
(Vaccinium elliotii) Fetterbush (Lyonia lucida)
Herbaceous (plants without bark) and shrubby
species located in the depressed areas
include Jack0in-the-pulpit (Arisaema
triphyllum) Lizards tail (Saururus
cernuus) Netted chain fern (Woodwardia
aerolata) Cinnamon fern (Osmunda
cinnamomea) Sensitive fern (Onoclea
sensibilis) Royal fern (Osmunda regalis)
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Pocosin Wetland
The pocosin wetland is located there. A
wetland community is typically located in a low
lying area that may be under water for extended
amounts of time. A pocosin wetland is unique
because it is found at a relatively high
elevation compared to other wetlands and has poor
soils. Under natural conditions, the plants in a
pocosin wetland are kept in check by fire. The
fire will burn the plants, allowing primary
succession to start over. However, this pocosin
will not be allowed to burn and it will grow
without restraint.
Tree species include Pond pine (Pinus
serotina) Longlead pine (Pinus palustris) Sweet
bay (Magnolia virginiana)
Low growing species include Redbay (Persea
palustris) Titi (Cyrilla racemiflora) Fetterbush L
aurel-leaved greenbrier (Smilax
laurifolia) Doghobble (Leucothoe racemosa)