Sec. 9.2.3. Watercourse Buffers

Natural Resource Buffers
1. General Rules for All Natural Resource Buffers
  Natural resource buffers are intended to provide an area where stormwater flows in a diffuse manner so that the stormwater runoff does not become channeled and infiltration of the stormwater and filtering of pollutants can take place. The following rules apply to all required natural resource buffers.
  1. Natural resource buffers shall be delineated on recorded final subdivision plats or at the time of development of the property.
  2. The City Council may reduce the width of natural resource buffers when it determines that the extent of the natural resource buffer yard will deprive the landowners of reasonable use of their property.
  3. The width of the natural resource buffer shall be measured perpendicularly to the flow of the watercourse and horizontally from the edge of the watercourse banks. When no watercourse banks exist, the centerline of the watercourse shall be used.
  4. Open space requirements for Conservation Development and Compact Development (Sec 2.5), and Planned Development (Sec. 4.7) may receive an open space bonus if the site exceeds the minimum natural resource buffer requirement. The open space bonus shall be based on a sliding scale factor from 0.9 (10% greater than required buffer) to 0.5 (100% greater than required buffer). The open space credit factor shall be determined as follows: (Area of required natural resource buffer)/(Area of proposed natural resource buffer) = Credit Factor. See required buffer area in Section 2.5.2.A.2. This credit factor may be multiplied times the required open space area and may meet up to 50% of Conservation Development, Compact Development, and Planned Development open space requirements. This bonus does not apply to open space requirements in Section 9.2, Stormwater Management.
2. Falls Watershed Protection Overlay District, Swift Creek Watershed Protection Overlay District and Conservation Management District Watercourse Buffers
  Natural resource buffers shall be established along primary and secondary watercourses in a -FWPOD, -SWPOD or CM District.
  1. Primary Watercourse Natural Resource Buffers
    Natural resource buffers along primary watercourses must meet the following standards.
    1. The buffer must be a minimum of 60 feet wide along each side of any watercourse draining 25 or more acres.
    2. The buffer must be a minimum of 35 feet wide along each side of any watercourse draining 5 or more acres but less than 25 acres.
    3. The buffer must be a minimum of 35 feet wide along each side of any watercourse which is a stream draining less than 5 acres.
    4. In the event that the property or subdivision contains impervious surface lot coverage in excess of 24% in a secondary reservoir watershed protection area, the buffer shall be no less than 100 feet wide along each side of the watercourse.
  2. Secondary Watercourse Natural Resource Buffers
    Unless part of a primary watercourse natural resource buffer, the secondary watercourse natural resource buffers consists of one or more of the following:
    1. Lands within special flood hazard areas (SFHAs) that adjoin primary watercourse natural resource buffers; or
    2. Lands with slopes 15% or greater, adjoining a primary watercourse natural resource buffers or a SFHA.
3. Metro-Park Overlay District Watercourse Buffers
  Natural resource buffers shall be established as primary tree conservation areas pursuant to Sec. 5.2.2.C.2. and Article 9.1. Tree Conservation along primary and secondary watercourses in a -MPOD. Required tree conservation areas shall meet the following standards.
  1. The primary tree conservation area must be a minimum of 50 feet wide along each side of any watercourse draining 25 or more acres.
  2. The primary tree conservation area must be a minimum of 25 feet wide along each side of any watercourse draining 5 or more acres but less than 25 acres.
4. Urban Water Supply Watershed Protection Overlay District Watercourse Buffers
  Natural resource buffers shall be established along primary and secondary watercourses in a -UWPOD. Required natural resource buffers shall meet the following standards.
  1. A minimum 30 foot wide natural resource buffer is required for all perennial waters indicated on the most recent versions of USGS 1:24,000 (7.5 minute) scale topographic maps.
  2. A minimum 100-foot wide natural resource buffer is required for all new development activities that exceed:
    1. Two dwelling units per acre or 20,000 square foot lot excluding roadway right-of-way; or
    2. 24% lot coverage for all other residential and nonresidential development.
  3. Within -UWPOD, these natural resource buffers do not apply to:
    1. New detached houses on a nonconforming lot of record;
    2. Expansion of existing development of on lots containing detached houses; and
    3. Activity in a single development that disturbs less than 1 acre.
Uses Allowed Within Natural Resource Buffers
No development, expansion of development or change in use may occur within a required natural resource buffer except as allowed below.
1. Property outside of a riparian water surface buffer, but situated within a required natural resource buffer, shall comply with all of the following.
  1. Driveways and vehicular surface areas, not including public streets, are allowed; provided that, all of the following are met:
    1. Any crossing is as close to perpendicular as practicable and insures minimal impact to the surrounding buffer; and
    2. The driveway or vehicular use area does not constitute more than 40% of the front yard area of any detached house.
  2. Fences, walls, statuary, monuments, fountains or signs shall be located outside any primary watercourse buffer.
  3. Garden crops involving cultivation shall be located outside any primary watercourse buffer.
  4. Greenways, sidewalks and walkways shall be located outside of a primary watercourse buffer and meet the requirements of Sec. 9.2.3.C.2. or shall be unpaved.
  5. New drainage ditches, roadside ditches and stormwater outfalls shall meet the requirements of Sec. 8.8.2.and Sec. 9.2.3.C.2.
  6. Playground equipment on single-unit or two-unit living lots.
  7. Ponds, stormwater management ponds, reservoirs, provided that, the standards of Sec. 9.5.1.C., Sec. 9.5.2.C.or Sec. 9.5.3.C. are met.
  8. Public streets, provided that the standards of Sec. 9.3.8., Sec. 9.3.9. and the Raleigh Street Design Manual are met.
  9. Railroad crossings.
  10. Stormwater control facilities and stormwater outfalls shall meet the requirements of Sec. 9.2.3.C.2. if there is no feasible alternate location.
  11. Utility lines.
    1. Non-electric utility lines are allowed, but if located in a -UWPOD,-FWPOD, -SWPOD or CM District, the utility lines must meet the standards of Sec. 9.2.3.C. if situated within a primary watercourse buffer area.
    2. Underground electrical utility lines are allowed, but if located in a -UWPOD, -FWPOD, -SWPOD or CM District, the underground utility lines must meet the standards of Sec. 9.2.3.C. if situated within a primary watercourse buffer area.
    3. Overhead electric utility lines are allowed, but if located in a -UWPOD, -FWPOD, -SWPOD or CM District, the overhead utility lines must meet the standards of Sec. 9.2.3.C. if situated within a primary watercourse buffer area.
  12. With the exception of any display area or any gasoline pump island, accessory structures and uses are allowed within a secondary watercourse of a -FWPOD, -SWPOD or CM District, provided that the following standards are met.
    1. i. No land-disturbing activity for any allowed use shall affect more than 12% of the portion of a lot within a secondary watercourse natural resource buffer.
    2. Land-disturbing activity on slopes between 15% and 20% may occur no closer than 80 feet to the edge of a watercourse.
    3. Land-disturbing activity on slopes greater than 20% may occur no closer than 95 feet to the edge of a watercourse.
    4. Upon a recommendation of the Stormwater Management Advisory Commission and approval by the City Council, land-disturbing activities may exceed the standards above; provided that the person submitting the request shows that the potential for stormwater infiltration within a site, the control of stormwater velocity and the restriction of sedimentation both during and after construction are equal to or greater than that which would have been achieved following standards in this Article. The applicant must also show that maintenance provisions are made to maintain the level of infiltration, velocity control and sedimentation on the site.
2. Property located within a riparian water surface buffer and within a required natural resource buffer, must also comply with Title 15A of the North Carolina Administrative Code Subarticle 2B, section .0714, as amended from time to time.
3. Property located inside of a riparian water surface buffer and outside a required natural resource buffer is subject to Title 15A of the North Carolina Administrative Code Subarticle 2B, section .0714, as amended from time to time.
Regulations Applied to Uses Allowed in Watercourse Buffers
1. Regulations Applying to All Natural Resource Buffers
  Persons who install utility mains shall submit a plan to the City proving that sediment loss during and after installation is less than would have been achieved if other locations outside the buffer were used.
2. Regulations Applying to Both Primary and Secondary Buffer Areas
  1. Stormwater Control Facilities in Primary or Secondary Areas
    Stormwater control facilities may be allowed within a primary or secondary area only if the following requirements are met:
    1. The constructed uses within the buffer area require the use of such facilities;
    2. The provisions of Sec. 9.4.4.G.4. require facilities in the buffer area;
    3. A wet pond is required by Sec. 9.5.1., Sec. 9.5.2.or Sec. 9.5.3.; or
    4. A lake or wet pond is created or preserved.
  2. Stormwater Control Facilities in Required Buffers
    Stormwater control facilities may be allowed within required buffer areas only if the following requirements are met.
    1. The velocity of the stormwater shall not exceed a non-erodible velocity, according to Sec. 9.4.4.G.3., beyond the outlet of the storm control facilities.
    2. Trees over 2-inch DBH which:
      1. a) Would be destroyed by installation of storm control facilities, but not including lakes or wet ponds;
      2. b) Lie within the greater distance of either a 7-foot radius or 1 foot in diameter for each inch of circumference of the tree measured from the outer edge of the grading limits of a storm drainage project shall be replaced by 1 new tree planted in the same general location, all to achieve the same effect as shown on an approved site plan. The planting must be a minimum caliper of 2 inches and be at least 8 feet tall at time of planting; and
      3. c) This provision shall not require trees to be planted on cleared land forming the basin of a wet pond or lake.
    3. Stormwater control facilities, which are permitted in the primary and secondary buffer area, shall comply with Sec. 9.5.1.C., Sec. 9.5.2.C. or Sec. 9.5.3.C.
Diffuse Stormwater Flow Required
1. All stormwater runoff from new man-made stormwater control facilities, including new ditches or canals, which flow into a watercourse natural resource buffer or into riparian surface water buffer shall be diffused flow so as not to concentrate stormwater or form gullies.
2. Diffuse flow shall be maintained.
3. The landowner or person in possession or control of the land shall be responsible for dispersing concentrated flow of stormwater runoff.
4. The landowner shall take corrective action to prevent the formation of erosion gullies and the landowner shall take corrective action to restore diffuse flow.
5. When diffuse flow is impractical to achieve, stormwater control facilities that attenuate the flow of stormwater runoff and control nitrogen may be approved by the City as an alternative means of compliance.
Watercourse Buffer Permits
1. No development, expansion of development or change in use may occur on a lot containing a natural resource buffer or open space area required as part of an approved stormwater control plan, without first being issued a written watercourse buffer permit from the City.
2. The City may not issue a watercourse buffer permit until the boundaries of any required natural resource buffer, riparian surface water buffer or permanently protected undisturbed open space areas that are adjacent to or encompass a work site are demarcated by a protective fence in the field.
3. No watercourse buffer permit may be issued for work in a riparian surface water buffer regulated by the State pursuant to Title 15A of the North Carolina Administrative Code Subarticle 2B, Section .0714 unless:
  1. The North Carolina Division of Water Quality has determined that surface waters are not present;
  2. The applicant provides sufficient documentation to demonstrate that the requested work is exempt under the rule;
  3. The North Carolina Division of Water Quality has determined that the requested work is allowable with mitigation under the rule; or
  4. The North Carolina Environmental Management Commission has issued a variance under the rule.
4. Before receiving a watercourse buffer permit, the applicant must present to the Engineering Services Department with a copy of the applicable determination of the North Carolina Division of Water Quality or a copy of the variance issued by the North Carolina Environmental Management Commission.

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