Floodplain Management


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 as geographic zones subject to varying levels of flood risk. Each zone reflects the severity or type of potential flooding in the area. The FEMA Map Service Center provides this information in the form of FEMA Flood Insurance Rate Maps (FIRMs) or Flood Hazard Boundary Map.

HUD’s regulations in 24 CFR Part 55 outline HUD’s procedures for complying with EO 11988. Part 55 applies to all HUD actions that could be harmed or cause harm if located in a floodplain, including but not limited to proposed acquisition, construction, demolition, improvement, disposition, and financing actions under any HUD program. The purpose of Part 55 is not in most cases to prohibit actions in a floodplain, but to provide the method for HUD projects to comply with EO 11988 and avoid unnecessary impacts.

Terminology and Basic Requirements

Special Flood Hazard Areas (SFHAs) are areas designated by FEMA as having a heightened risk of flooding.


100-Year Floodplains (or 1 Percent Annual Chance Floodplains) are areas near lakes, rivers, streams, or other bodies of water with at least a 1% chance of flood occurrence in any given year. HUD projects within a 100-Year Floodplain must complete the 8-Step Decisionmaking Process to determine whether there are practicable alternatives to locating the project in the floodplain, unless an exception in section 55.12 applies.


A Regulatory Floodway comprises the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. This is the segment of the floodplain that will generally carry flow of flood waters during a flood and is typically the area of greatest risk to structures in the floodplain. HUD financial assistance is prohibited in floodways unless an exception in section 55.12(c) applies or the project is a functionally dependent use (e.g. dams, marinas, and port facilities) or a floodplain function restoration activity.


Coastal High Hazard Areas (or V Zones) are areas along the coasts subject to inundation by the 1% annual chance flood event with additional hazards associated with storm or tidal induced waves... Because of the increased risks associated with V Zones, Part 55 prohibits critical actions and new construction in these areas unless an exception in section 55.12(c) applies or the project is a functionally dependent use, and otherwise requires the action to be designed for location in a Coastal High Hazard Area.

Non-Special Flood Hazard Areas are areas with moderate-to-low risk of flooding; however, it is important to remember that floods still occur frequently in these areas. One in four NFIP claims occur outside of SFHAs.


500-Year Floodplains (or .2 Percent Annual Chance Floodplains) are areas with at least a .2% chance of flood occurrence in any given year. HUD requires critical actions (e.g. hospitals, nursing homes, police stations, fire stations, and roadways providing sole egress from flood-prone areas) to comply with Part 55 when they are located in the 500-year floodplain.

For more information on basic responsibilities and definitions, refer to 24 CFR 55.1 and 55.2. For more detailed information on the different types of floodplains, see FEMA Flood Zones.

Complying with 24 CFR Part 55

HUD has prepared flow charts illustrating how to comply with Part 55 for non-critical actions and critical actions.

Step 1: Determine whether any of the exceptions at 55.12(c) apply.

Under 55.12(c), certain projects are exempt from Part 55. The projects are not required to complete the 8-Step Process, and they may be able to proceed despite the presence of a floodway or coastal high hazard area.

Activities listed in 55.12(c) include floodplain restoration, minor amendments to previously approved actions, sites where FEMA has issued a final Letter of Map Revision or final Letter of Map Amendment, actions that are Categorically Excluded Not Subject to 50.4 or 58.5, and sites where the “incidental floodplain exception” applies.

The incidental floodplain exception may exempt a project from Part 55 where only a small portion of the project site contains a floodplain. It is important to note that the entire floodplain must be incidental, meaning that this exception does not apply if any buildings or improvements exist within the SFHA. Projects may be exempted under the incidental floodplain exception if:

  1. No new or existing buildings or improvements occupy or modify the 100-year floodplain, floodway, coastal high hazard area, or – for critical actions – the 500-year floodplain
  2. Provisions are made for site drainage that will not adversely affect any wetland, AND
  3. A permanent covenant is placed on the property's continued use to preserve the floodplain.

For a visual representation of the incidental floodplain exception, see Incidental Floodplain Exception, Illustrated.

Step 2: Determine whether the project site contains a floodplain.

If the project is not exempt under section 55.12(c), use a FEMA Flood Insurance Rate Map (FIRM) to determine whether the project is in or near a floodplain. In most areas, Flood Insurance Rate Maps (FIRMs) are available online through the FEMA Map Service Center. When FEMA provides Advisory Base Flood Elevations (ABFE) or preliminary FIRMs and studies, HUD or the responsible entity must use the latest of these sources unless the ABFE or preliminary FIRM allow a lower Base Flood Elevation (BFE) than the current FIRM and FIS. Where available, FEMA maps indicate floodplains as follows:

  • 100-year floodplains are designated as Zone A1–30, AE, A, AH, AO, AR, or A99.
  • 500-year floodplains are designated as Zone B or a shaded Zone X.
  • Floodways are designated as Zone AE hatched.
  • Coastal high hazard areas are designated on a Flood Insurance Rate Map (FIRM) under FEMA regulations as Zone V1–30, VE, or V.

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/or 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.

Step 3: Determine if the 8-Step Process is required.

Under section 55.12, certain actions must comply with Part 55 but are not required to complete the full 8-Step Process.

  • Section 55.12(a) lists activities that must complete the modified 5-Step Process: these actions are not required to provide public notice or consider alternatives, but must complete the other steps in the 8-Step Process. These include disposition of properties, purchase and refinance of existing multifamily housing or healthcare facilities, and minor improvements to multifamily housing and nonresidential structures.
  • Section 55.12(b) lists project types that must comply with the basic restrictions in Part 55 (i.e. the prohibitions on projects in floodways and critical actions in coastal high hazard areas) but which are not required to complete the 5- or 8-Step Processes. These include acquisition and refinance of existing single family properties, minor improvements to single family properties, and leasing.

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 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 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 floodplain function restoration activity or a 55.12(c) exception applies. If it is a functionally dependent use or restoration activity, 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 existing structure, an improvement of an existing structure or reconstruction following a disaster in accordance with 24 CFR 55.1(c)(3)(i). Refer to 55.1(c)(3)(i) and (ii) for construction requirements for projects permitted in coastal high hazard areas. An 8 Step Process must be performed unless an exception applies.

Step 4: Complete the 8-Step Process and identify mitigation requirements.

Review Section 55.20 and the resources on this page for information on completing the 8-Step Process. Note that although Part 55 does not contain elevation requirements for non-critical actions, projects involving new construction and substantial improvements (as defined in 55.2(b)(10)) must be elevated or, for nonresidential structures, floodproofed to the base flood elevation of the floodplain in order to get flood insurance from FEMA.

If the project involves new construction or substantial improvement (as defined in 24 CFR 55.2(b)(10), NFIP regulations require that the affected structure(s) be elevated to the base flood elevation. State or local law or program policy may require additional elevation (or “freeboard”) beyond the minimum elevation requirements set by FEMA.

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 and an applicable citation to 55.12(b) demonstrating that the 8-Step Process is not required.
  • A FEMA map showing the project is located in a Special Flood Hazard Area, documentation that the 5-Step Process was completed, and the applicable citation to 55.12(a).
  • 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.

View Floodplain Management - Worksheet.

View Floodplain Management - Partner Worksheet.

Related Resources

Methods to Minimize Impacts and Restore and Preserve Floodplains

Other Materials and Sources