Use regulations

A. Reference to existing regulations.
- (1) The special flood hazard areas are established as a floodplain overlay district. All development in the district, including structural and nonstructural activities, whether permitted by right or by special permit, must be in compliance with the following:
  - (a) Rhode Island State Building Code (as established under R.I.G.L. § 23-27.3);
  - (b) Freshwater Wetlands Act, Department of Environmental Management (R.I.G.L. § 46-23-6); and
  - (c) Minimum Standards Related to Individual Sewage Disposal Systems, Department of Environmental Management (R.I.G.L. § 46-12).
- (2) Any variances from the provisions and requirements of the above-referenced state regulations may only be granted in accordance with the required variance procedures of these state regulations.
B. Other use regulations.
- (1) Within Zones AH and AO on the FIRM, adequate drainage paths must be provided around structures on slopes, to guide floodwaters around and away from proposed structures.
- (2) Within Zone AO on the FIRM, new and substantially improved residential structures shall have their lowest floor at least as high as the FIRM's depth number above the highest adjacent grade and nonresidential structures shall be elevated or floodproofed above the highest adjacent grade to at least as high as the depth number on the FIRM. On FIRMs without a depth number for the AO Zone, structures shall be elevated or floodproofed to at least two feet above the highest adjacent grade.
- (3) In Zones A1-30 and AE, along watercourses that have a regulatory floodway designated on the Town of Johnston FIRM or Flood Boundary and Floodway Map, encroachments are prohibited in the regulatory floodway which would result in any increase in flood levels within the community during the occurrence of the base flood discharge.
- (4) All subdivision proposals must be designed to ensure that:
  - (a) Such proposals minimize flood damage;
  - (b) All public utilities and facilities are located and constructed to minimize or eliminate flood damage; and
  - (c) Adequate drainage is provided to reduce exposure to flood hazards.
- (5) Detached accessory structures in Zones A, AE, A1-30, AO, and AH (i.e., garages, sheds) do not have to meet the elevation or dry floodproofing requirement if the following standards are met:
  - (a) The structure is no more than 100 square feet in size and has a value less than $1,000.
  - (b) The structure has unfinished interiors and must not be used for human habitation. An apartment, office or other finished space over a detached garage is considered human habitation and would require the structure to be elevated.
  - (c) The structure is used solely for the parking of vehicles and/or limited storage.
  - (d) The accessory must be wet floodproofed and designed to allow for the automatic entry and exit of floodwater.
  - (e) The accessory structure shall be firmly anchored to prevent flotation, collapse, and lateral movement.
  - (f) Service facilities such as electrical, mechanical, and heating equipment must be elevated or floodproofed to or above the base flood elevation.
  - (g) The structure must not increase the flood levels in the floodway.
- (6) Existing contour intervals of site and elevations of existing structures must be included on the plan proposal.
C. Base flood elevation and floodway data.
- (1) Floodway data. In Zones A, A1-30, and AE, along watercourses that have not had a regulatory floodway designated, the best available federal, state, local, or other floodway data shall be used to prohibit encroachments in floodways which would result in any increase in flood levels within the community during the occurrence of the base flood discharge.
- (2) Base flood elevation data. Base flood elevation data is required for subdivision proposals or other developments greater than 50 lots or five acres, whichever is the lesser, within unnumbered A Zones.
- (3) Base flood elevations in A Zones. In the absence of FEMA BFE data and floodway data, the best available federal, state, local, or other BFE or floodway data shall be used as the basis for elevating residential and nonresidential structures to or above the base flood level and for floodproofing nonresidential structures to or above the base flood level.