Floodways or Non-Encroachment Areas

42-235.6 Floodways or Non-encroachment Areas

Areas designated as floodways or non-encroachment areas are located within the Special Flood Hazard Areas established in §42-233.2 (Basis for Establishing the Special Flood Hazard Areas). The floodways and non- encroachment areas are extremely hazardous areas due to the velocity of floodwaters that have erosion potential and carry debris and potential projectiles. The following provisions, in addition to the standards outlined in §42-235.1 (General Standards) and §42-235.2 (Specific Standards), shall apply to all development within such areas.

  • No encroachments, including fill, new construction or substantial improvements shall be permitted unless:
    • The structure is a functionally dependent facility, excluding enclosed structures, new water and sewer lines provided no viable alternative exists, recreational uses (excluding enclosed structures) and stream bank restoration projects, provided the requirements of §42-235.2 (Specific Standards) and §42-235.6 (Floodways or Non-Encroachment Areas) A (2) are met;
    • The parcel owner first having obtained and submitted to the Floodplain Administrator an acceptable certification by a registered professional engineer proving that the anticipated encroachment(s) shall not result in any increase in the elevation of the regulatory flood during an occurrence of the base flood. The Floodplain Administrator shall require documentation of the certification which shall include either:
    • A completed “engineering no-rise” certification form as published by FEMA, or acceptable alternative form approved by FEMA together with:
    • Technical documentation in the form of detailed site and construction plans, showing that all requirements of this Subpart A are met;
    • Technical documentation in the form of hydraulic analysis of the existing and proposed conditions. This documentation shall be either: complete runs of existing and proposed conditions using the HEC II/HEC-RAS step backwater analysis computer program as prepared by the US Army Corps of Engineers for the analysis of flow plan hydraulics; or
    • An alternative method currently approved by FEMA for use in the revision process for FEMA flood maps. In this case, the engineer shall provide a letter from FEMA indicating that the method used is acceptable; or
  • A Conditional Letter of Map Revision (CLOMR) which has been approved by FEMA. A Letter of Map Revision (LOMR) must also be obtained upon completion of the proposed encroachment.

If 235.6 (Floodways or Non-encroachment Areas) A is satisfied, all development shall comply with all applicable flood hazard reduction provisions of this Subpart A.

No manufactured/mobile homes shall be permitted, except replacement manufactured/mobile homes in an existing manufactured home park or subdivision, provided the following provisions are met:

  • The anchoring and the elevation standards of §42-235.2 (Specific Standards) C (Manufactured/Mobile Homes); and
  • The no encroachment standard of §42-235.6 (Floodways of Non-encroachment Areas).

Supporting Documents

PDF icon LIMITED DETAILED STUDY METHOD TECHNICAL DOCUMENT (1 MB)