Water Supply Watershed Protection
Frequently Asked
Questions
Is
my property located within a water supply watershed? Which one?
All land is located within a watershed of one kind or another, but only twenty
percent of North Carolina's land area is classified as being within water
supply watersheds. Check with your local government to see if the
watershed rules are in effect in your area. If so, the local government will
have a map showing the boundaries of the watershed(s). NCOneMap
or the Stormwater Program Interactive Map Viewer may be able to show you if you are in or out as well. If you have further
questions, contact us.
Will this program stop development?
No! The only classification which prohibits new development (WS-I)
contains no privately-owned land. For other classifications, using density bonuses,
density averaging or other flexibility measures built into the rules gives communities
and developers ample possiblities for growth. Refer to the water
supply watershed classification table for details.
What is "built-upon area?"
How do I calculate it?
Built-upon area is a measure of the hard surfaces or impervious cover for a site.
For each piece of land, divide the amount (area) of impervious surface (i.e.:
structures, roads, parking lots) located on-site by the total land area under
consideration. Multiply the resulting fraction by 100 to get the percent built-upon
area. Refer to Streamlines Vol. 1, no. 5
for more information regarding impervious surfaces.
What is the "critical
area?"
Critical area is the land adjacent to a water supply intake where risk associated
with pollution is greater than from remaining portions of the watershed. Critical
area is defined as land within one-half mile upstream and draining to a river
intake or within one-half mile and draining to the normal pool elevation of water
supply reservoirs. Critical areas are more restrictive than areas outside this
area.
What is the "protected
area?"
Protected areas are only located within WS-IV watersheds.
A protected area is defined as land within five miles and draining to the normal
pool elevation of water supplies/reservoirs, or within ten miles upstream and
draining to a river intake.
What
is meant by the term "buffer area?"
The purpose of a buffer is to provide a vegetated area along perennial streams
through which stormwater runoff can flow in a diffuse manner, infiltrate into
the soil, and allow filtration of pollutants. There are two types of buffer
requirements: an agricultural buffer and a development buffer. For agriculture,
the buffer is only required in the critical area and is measured from the stream
bank landward for a distance of ten feet. For development activities throughout
the watershed, buffers are required along all perennial waters with a minimum
width of thirty (30) feet for low density development and a minimum one-hundred
(100) feet for high density development (this includes use of the 10/70). The
buffer is measured perpendicularly from the streambank (or from the normal pool
elevation of reservoirs) and serves as a setback for new structures such as
houses, barns, and other buildings (see buffer
graphic in Streamlines Vol. 3, no. 1).
Property owners are encouraged, but not required, to maintain at least the first
25 feet of the buffer next to the stream in a naturally vegetated or undisturbed
state. Property owners and land developers are recommended to leave the buffer
areas in public ownership and/or to dedicate them as a linear greenway
or park. For more information on how buffers can help water quality, please
refer to Streamlines Vol. 1, no.
4.
What is the 10/70
provision? How does it work?
With the 10/70 Provision, a local government can use 10% of the non-critical area
of each watershed within its jurisdiction for new development and expansions to
existing development up to a 70% built-upon area limit -- without stormwater control
-- if using the low-density option throughout the remainder of the watershed.
The 10/70 provision is available within WS-II, WS-III and those WS-IV water supplies
where the local government allows only development using the low density option.
Please note that local governments can use this technique to "swap" publicly-owned,
flood-prone, or otherwise undevelopable land in order to target growth at a higher
density elsewhere within the watershed. The 10/70 provision is considered a "high
density" option, and therefore requires a 100 foot buffer along all perennial
streams when being utilized.
What is the difference
between the low and high density options?
The high density development option allows for more built-upon area on a site
through the use of stormwater management techniques to mitigate the effects of
the increased impervious surface and the resulting increased rainfall runoff.
Depending upon the watershed classification, low density development may allow
up to 2 dwelling units per acre (24% built-upon area). With the high density option,
development can potentially reach a 70% maximum built-upon area, depending upon
the watershed classification. For a detailed discussion about using the high density
option, please refer to Streamlines Vol. 1,
no. 3. The water supply watershed classification
table has more details regarding low and high density built-upon area limits
for the various watershed classifications.
What are best management
practices (BMPs)?
BMPs are structural or non-structural management-based measures used singularly
or in combination to reduce nonpoint source inputs to receiving waters in order
to achieve water quality protection goals. Streamlines
Vol. 1, no. 2 contains more information regarding alternative stormwater management
techniques. See the Stormwater Best Management Practices Manual put out by the Division of Water Quality.
Where can I get more information
on watersheds and water quality?
Take a look at our Reference page which has many
links to a variety of sources of information.
Do you have a question about the water supply watershed protection program
that is not answered here? Click here
to send us an e-mail message. We'll answer it as soon as possible. Thanks.
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http://h2o.enr.state.nc.us/wswp/FAQs.html (Last
Updated: November 15, 2003)