Ten Towns Committee
Model Steep Slope Ordinance
Flashing icon that says: NewOctober 22, 2003.  This model ordinance has been prepared by the 10 Towns Great Swamp Watershed Committee as a prototype for adoption by its municipal government members.


The purpose of this ordinance is to regulate the intensity of use in areas of steeply sloping terrain in order to limit soil loss, erosion, excessive stormwater runoff, the degradation of surface water and to maintain the natural topography and drainage patterns of land.


This ordinance shall be applicable to any subdivision, site plan or land disturbance application located in the municipality as defined in the Municipal Land Use Law or any project defined by the Soil Erosion and Sediment Control Act. Land disturbance for the purpose of this ordinance shall mean any activity involving the clearing, cutting, excavation, grading, filling, storing, transporting of land or any other activity which causes land to be exposed to the danger of erosion.


  1. On slopes of 25% or greater, no development, regrading or stripping of vegetation shall be permitted. Any disturbance for roadway crossings or utility construction in areas of 25% slopes or greater are considered variance conditions and the applicant must affirmatively demonstrate that the roadway or utility improvements are necessary in the sloped area. The sloped area to be developed, regraded or stripped of vegetation shall be drawn on the development plans for each individual lot.
  2. The maximum disturbance allowed in slope areas between 20.0% to 24.9% shall be 20%.
  3. The maximum disturbance allowed in slope areas between 15.0% and 19.9% shall be 40%.
  4. The maximum disturbance allowed in slope areas between 0 to 14.9% may be 100%.
  5. Site design and grading on slopes greater than 15% shall provide the minimum disruption of view corridors and scenic vistas and shall preserve significant natural topographic features to the greatest extent possible.
  6. Steep Slope disturbance of an area less than _______ square feet shall be permitted on any parcel.


For all earth moving activities on slopes of 15% or greater, the Applicant shall submit a site plan prepared by a Professional Engineer. The site plan submitted shall be reviewed by the Municipal Engineer. The Municipal Engineer shall determine if the site plan as submitted is complete and in conformance with the ordinance requirements. The Municipal Engineer shall recommend acceptance or rejection of the plan or may require that specific conditions be complied with in order for the plan to merit acceptance. The Applicant’s site plan as prepared by a Professional Engineer will include at a minimum the following:

  1. Slopes in classes of 0-14.9%, 15-24.9% and greater than 25% based on two foot (2’) contour analyzed on ten foot (10’) vertical intervals.
  2. Location of all waterbodies including but not limited to streams, lakes and wetlands.
  3. Existing natural and topographic features.
  4. Location of all proposed and existing buildings and streets.
  5. Location of all existing vegetation including meadow, forest and scrub lands broken down by those areas of vegetation which will be removed as well as vegetation to be preserved; specifications for revegetation shall also be included.
  6. Specific methods which will be utilized to control soil erosion and sedimentation, soil loss and excessive stormwater runoff both during and after construction.
  7. A statement and description of the stability of the soils on site and the appropriateness of the construction method proposed.
  8. Hydrology, drainage and flooding analysis to include a statement on the effect of the proposed development upon water bodies or wetlands in the vicinity of the project.
  9. A statement describing the underlying geology attesting to the stability of the site.
  10. Calculations of the area of proposed disturbance of each slope class on each proposed lot as well as within any proposed road right-of-way.
  11. Grading plan for the construction site and all access routes.
The site plan submitted shall be reviewed by the municipal engineer. The municipal engineer shall accept or reject the plan as submitted or may require that specific conditions be complied with in order for the plan to meet approval.

No building permit shall be issued and no grading or site clearing shall occur until a site plan including all of the above items has been reviewed and approved by the municipality.


All development proposals which propose development on steep slopes shall conform to the following performance standards:

  1. Lands to be preserved in 100 percent open space due to the presence of steep slopes may be offered for dedication to the municipality, a private land trust or a non-profit agency in order to preserve and maintain the area in its natural state.
  2. The use of conservation easements on steep slopes shall be encouraged to preserve the area in perpetuity.


Land development plans which were approved prior to the adoption date of this ordinance shall be exempt from these requirements.


Development approvals issued pursuant to this ordinance are to be considered an integral part of development approvals under the subdivision and site plan review process and do not relieve the applicant of the responsibility to secure required permits or approvals for activities regulated by other applicable codes, rules, acts or ordinances. In their interpretation and application, the provisions of this ordinance shall be held to be the minimum requirements for the promotion of the public health, safety, general welfare and the protection of water quality.


If the provisions of any part of this ordinance shall be judged invalid by a court of competent jurisdiction, such order of judgment shall not affect or invalidate the remainder of this ordinance.

Following is the letter which transmitted this proposed ordinance to the member towns.

October 27, 2003

Re: Steep Slope Model Ordinance

Dear Mayor ________ and Members of the Governing Body,

At its October 22, 2003 meeting, the Ten Towns Great Swamp Watershed Management Committee unanimously approved the attached model ordinance and directed that it be distributed to all member municipalities with a request for prompt consideration that it be included in your zoning ordinances.

The ordinance requires that whenever there is land disturbance as defined in the Municipal Land Use Ordinance certain procedures must be followed to protect the receiving water bodies prior to approval. The proposed ordinance prohibits any development on slopes of 25% or greater and requires developers to adhere to variance proofs for roadway and utility improvements in areas of 25% slopes or greater.

Your attention is requested to Section 3.F which will require your judgment. The Committee believes that each municipality should decide if it wishes to exempt small areas that contain rock outcroppings, man made steep slopes or other small land risings from the provisions of this model ordinance. Some communities exempt 1,000 square feet while others have kept the number to 500 square feet. There are some municipalities who may wish to require more stringent requirements and have no exemptions. This is a policy matter for each community.

Your community has been very supportive in taking the recommendations for model environmental ordinances from the Ten Towns Committee. This model steep slope ordinance is our latest effort to encourage all member municipalities to assist us in improving and protecting the water quality of the Great Swamp Watershed.

Your current zoning ordinance may already contain certain steep slope provisions and if it does, we ask that you compare the model ordinance with your current requirements and adopt the more stringent requirements. The model ordinance should be considered as minimum standards acceptable for protecting water quality.

If you have any questions on this or need additional information, please contact me or your Ten Towns representative listed below.

Sincerely yours,

Executive Director

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Steep Slope Ordinance
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