Floodplain Management

Introduction

Executive Order 11988 - Floodplain Management requires Federal activities to avoid impacts to floodplains and to avoid direct and indirect support of floodplain development to the extent practicable. The Federal Emergency Management Agency (FEMA) designates floodplains. The FEMA Map Service Center provides this information in the form of FEMA Flood Insurance Rate Maps (FIRMs).

HUD Guidance

Do any of the exceptions  at 55.12(c) apply?

If not, does your project occur in a floodplain? Use a Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) to make the determination. For projects in areas not mapped by the FEMA, use the best available information to determine floodplain information.  Include in your documentation a discussion of why this is the best available information for the site.

Sources which merit investigation include the files and studies of other federal agencies, such as the U. S. Army Corps of Engineers, the Tennessee Valley Authority, the Soil Conservation Service and the U. S. Geological Survey. These agencies have prepared flood hazard studies for several thousand localities and, through their technical assistance programs, hydrologic studies, soil surveys, and other investigations have collected or developed other floodplain information for numerous sites and areas. Information on the availability of floodplain data may be obtained by contacting the appropriate agency officer listed in Appendix A of this document. States and communities are also sources of information on past flood 'experiences within their boundaries and are particularly knowledgeable about areas subject to high risk flood hazards such as alluvial fans, high velocity flows, mudflows and mudslides, ice jams, subsidence and liquefaction. For further information, see Further Advice on Executive Order 11988 Floodplain Management (Interagency Task Force on Floodplain Management).

  • 100-year floodplain means the floodplain of concern for this part and is the area subject to a one percent or greater chance of flooding in any given year.  The area is designated on a Flood Insurance Rate Map (FIRM) under FEMA regulations as Zone A1–30, AE, A, AH, AO, AR, or A99.
  • 500-year floodplain means the minimum floodplain of concern for Critical Actions and is the area subject to inundation from a flood having a 0.2 percent chance of occurring in any given year.  The area is designated on a Flood Insurance Rate Map (FIRM) under FEMA regulations as Zone B or a shaded Zone X.
  • Floodway means that portion of the floodplain which is effective in carrying flow, where the flood hazard is generally the greatest, and where water depths and velocities are the highest. The term “floodway” as used here is consistent with “regulatory floodways” as identified by FEMA.
  • Coastal high hazard area means the area subject to high velocity waters, including but not limited to hurricane wave wash or tsunamis. The area is designated on a Flood Insurance Rate Map (FIRM) under FEMA regulations as Zone V1–30, VE, or V.

If the project occurs in a 100-year floodplain (A Zone), an 8-Step Process is required unless it is inapplicable per 55.12(b) or if the 5-Step Process is applicable per 55.12(a).

If the project occurs in a 500-year floodplain (B Zone or shaded X Zone), the 8-Step Process is required for critical actions unless it is inapplicable per 55.12(b) or if the 5-Step Process is applicable per 55.12(a). If the project occurs in a floodway, federal assistance may not be used at this location unless the project is a functionally dependent use or a 55.12(c) exception applies. The 8-Step Process is required.

If the project occurs in a Coastal High Hazard Area (V Zone), federal assistance may not be used at this location if the project is a critical action. For all other actions, financial assistance is prohibited unless the activity is an improvement of an existing structure or reconstruction following a disaster in accordance with 24 CFR 55.1(c)(3)(i). New construction must be designed to FEMA standards for V Zones at 44 CFR 60.3(e), and an 8 Step Process must be performed unless an exception applies. Existing construction that will be improved must have met FEMA elevation and construction standards for coastal high hazard areas or other standards applicable at the time of construction.

Compliance and Documentation

The environmental review record should contain one of the following:

  • Documentation supporting the determination that an exception at 55.12(c) applies.
  • A FEMA map showing the project is not located in a Special Flood Hazard Area.
  • A FEMA map showing the project is located in a Special Flood Hazard Area along with documentation of the 8-Step Process and required notices. If the 5-Step Process is applicable, provide documentation of the 5-Step Process and indicate the applicable citation. If the 8-Step Process is inapplicable, indicate the applicable citation and document the determination.

View Floodplain Management - Worksheet.

View Floodplain Management - Partner Worksheet.

Related Resources

Methods to Minimize Impacts and Restore and Preserve Floodplains

Other Materials and Sources