P1.2: Protect Floodplain Functions

(Required)

INTENT

Protect floodplain functions (e.g., storage, habitat, water quality benefits) by limiting new development within the 100-year floodplain of all types of waterways and watercourses.

REQUIREMENTS

Case 1: Sites without floodplain

• Locate the project on a site that does not contain any land within a 100-year floodplain as defined and mapped by the Federal Emergency Management Agency (FEMA) or a local or state floodplain management agency map, whichever is more stringent (or local equivalent for projects outside the United States).
• Ensure the section of the site assessment (see Pre-Design P2.2: Conduct a pre-design site assessment) is complete, including documentation that the site is not located within a 100-year floodplain.

Case 2: Previously developed and brownfield sites within floodplain

• Locate the project on a previously developed or brownfield site.
  • Demonstrate how the proposed development or redevelopment activities within the floodplain mitigate and improve existing floodplain conditions. Such activities must maintain or increase existing floodplain storage, improve water quality, and be designed so as not to be damaged by floods. Activities must not increase flood elevations.
  • Comply with the National Flood Insurance Program (NFIP) requirements for developing any structures within the 100-year floodplain (or local equivalent for projects outside the United States).
• Ensure the section of the site assessment (see Pre-Design P2.2: Conduct a pre-design site assessment) is complete and documents the location of the 100-year floodplain.
• Ensure the section of the site maintenance plan (see O+M P8.1: Plan for sustainable site maintenance) is complete and describes the on-going management activities to protect the integrity of the floodplain functions.

Case 3: Greenfield sites within floodplain

• Ensure the section of the site assessment (see Pre-Design P2.2: Conduct a pre-design site assessment) is complete and documents the location of the 100-year floodplain.
• Designate Vegetation and Soil Protection Zones (VSPZs) for 90 percent of the land within the 100-year floodplain (see Pre-Design P2.3: Designate and communicate VSPZs).
• Demonstrate that any minimal impact site development within the VSPZ improves existing floodplain conditions, which means it maintains or increases existing floodplain storage, improves water quality, is designed so as not to be damaged by floods, and does not singularly or cumulatively increase flood elevations.
• Comply with the National Flood Insurance Program (NFIP) requirements for developing any structures within the 100-year floodplain (or local equivalent for projects outside the United States).
• Ensure the section of the site maintenance plan (see O+M P8.1: Plan for sustainable site maintenance) is complete and describes the on-going management activities to protect the integrity of the VSPZs and the floodplain functions.

RECOMMENDED STRATEGIES

• Design the site to limit development and disturbance within the 100-year floodplain.
• Design new development, such as a trail or boardwalk, in such a way that it will not be damaged by flooding or result in a negative impact to existing floodplain storage or conveyance.
• Re-establish areas of vegetated floodplain on brownfield or previously developed sites, and manage invasive plant species where necessary.
• Carefully situate new development to avoid causing erosion and directing sediment and potential contaminants from stormwater runoff into receiving waters.