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More Information: Topography in the SNAD
Updated: May 5, 2021
This overview of SNAD regulations is provided for informational purposes only—the actual regulations are much more complex than this overview. Contact the Bronx Office of City Planning, at 718-220-8500, with your specific project plans and a description of your property, to ensure that you comply with all zoning requirements. City Planning will guide you through the approval and permitting process.
Topography (including steep slopes)

Modifications to a slope can affect storm water and groundwater drainage patterns, soil conditions, and vegetation health. In the SNAD, lots are characterized as:
Tier I - average slopes of < 10 %
Tier II - average slopes of 10 % or greater (includes "steep slopes")
steep slopes - slopes of 25 % or greater
Maximum Lot Coverage Lot Coverage is the portion of a zoning lot which, when viewed from above, is covered by a building or portion of a building. Slope Zoning District Permitted Maximum Lot Coverage steep slope R1, R2, R3 12.5 %
steep slope R4 20.0 %
10 - 14.9 % R1 - R4 varies from 22.5 to 36 %
15 - 19.9 % R1 - R4 varies from 20.0 to 32 %
20 - 24.9 % R1 - R4 varies from 17.5 to 28 %
Topography Category Grading Regulation Zoning Regulation
Projects that do not require Review by Department of City Planning Section 105-021, b
a building permit, such as required for changes to topography
some swimming pools, of more than two feet
garden sheds, or fences
Tier I Sites: Authorization from the City Planning Section 105-421
Projects that require a Commission required for any
building permit modification of existing topography.
Tier II sites: Authorization from the City Planning
Projects that require a Commission or any grading beyond 15 feet
building permit of the location of a building foundation
(Exception: driveways and private roads)
Grading within 15 feet of a foundation Section 105-34
Grading within 15 feet of a foundation
slopes, compaction of fill, retaining walls,
and other grading elements
Driveways and private roads Section 105-35
Topsoil is protected from erosion during construction:
"Any exposed earth shall have straw, jute matting , or geotextiles placed on it within two days of exposure and be seeded with annual rye grass during construction." (Section 105-36, (f))" "A development on a Tier II site, that needs an authorization, must inst
all one of the following erosion and sedimentation control measures: benches and berms, diversion channels, debris or sediment basins, retention ponds, or grassed waterways or outlets. (Sect. 105 -37)"