Executive Order 11988 Floodplain Management

Executive Order 11988 (EO 11988), issued in 1977, requires federal agencies to “avoid to the extent possible the long and short term adverse impacts associated with the occupancy and modification of floodplains and to avoid direct or indirect support of floodplain development wherever there is a practicable alternative.” The order is implemented by Emergency Management and Assistance regulations 44 CFR 9, “Floodplain Management and Protection of Wetlands”, which are administered by the Federal Emergency Management Agency (FEMA). EO 11988 is also incorporated into FHWA regulations under 23 CFR 650, “Bridges, Structures, and Hydraulics”.

When It Is Required

Any project that involves a federal action (such as a federally funded highway project) must assess impacts to floodplains that could occur from a proposed action. Floodplains, in this case, are the areas subject to flooding by the base flood, or the flood having a 1% chance of being exceeded in any given year (also referred to as the 100-year flood). Floodplain mapping is available from FEMA at www.fema.gov and on the Vermont Natural Resources Atlas.

Permit Process

There is no permit process for compliance with EO 11988, and no direct submittal to FEMA. Compliance is typically documented as part of a National Environmental Policy Act (NEPA) document. 44 CFR 9 specifies the steps that must be followed to demonstrate compliance with EO 11988, summarized here:

  1. Determine whether a proposed action is located in a floodplain.
  2. Conduct early public review, including public notice. (This is not typically required for projects with minimal impacts.)
  3. Identify and evaluate practicable alternatives.
  4. Identify direct and indirect impacts associated with filling or modifying floodplains.
  5. Minimize potential adverse impacts.
  6. Reevaluate the proposed action to determine if it is still the most practicable alternative.
  7. Present the findings and a public explanation. (Documentation within the NEPA documents is usually sufficient.)
  8. Preview the implementation and post-implementation phases of the proposed action to ensure that the proposed mitigation is fully implemented.

23 CFR 650 101-117 further specifies the steps that must be followed to demonstrate compliance with NEPA for floodplain impacts in FHWA administered projects. The regulations state that the design selected for an encroachment “shall be supported by analyses of design alternatives with consideration given to capital costs and risks, and to other economic, engineering, social and environmental concerns.” The regulations provide design standards for highway and bridge designs and for the level of detail for design studies that must be made in the case of floodplain or floodway encroachment.

Related Programs

Regulatory programs with overlapping jurisdiction with Executive Order 11988 include, but are not necessarily limited to, the following:

For More Information

Federal Emergency Management Agency

99 High Street, 5th Floor

Boston, MA 02110



Vermont Center for Geographic Information has digital floodplain mapping.


Vermont ANR Flood Hazard Management is Vermont’s flood hazard program.


Municipal Guide to Fluvial Erosion Hazard Mitigation


FEMA Environmental and Historic Preservation (EHP) Program: