Main Content

Coastal Flood Risk Study Process

In this page you will find information about the work to scientifically study and understand coastal flood hazards as part of FEMA’s Risk Mapping, Assessment, and Planning (Risk MAP) effort in partnership with other federal agencies, states, regional authorities, tribal nations, territories, communities and non-profit organizations. This page is intended for home and property owners, community officials, insurance professionals and lenders, and other stakeholders interested in learning about the coastal flood study process and coastal flood hazards.

A map of the United States that illustrates when counties along the coasts will be receiving new flood mapping data, updated January 2019.
<p>A map of the United States that illustrates when counties along the coasts will be receiving new flood mapping data, updated January 2019.</p> Download Original

Starting in the late 2000s, FEMA has been updating Flood Insurance Studies (FISs) and Flood Insurance Rate Maps (FIRMs) for the entire populated coastline of the country to provide improved flood hazard information to coastal communities along the Atlantic and Pacific Oceans, the Gulf of Mexico, and the Great Lakes. The need for updated flood information was multifaceted. The expansion of communities into undeveloped coastal areas increased during the last several decades, putting many new citizens at risk from coastal storms and flooding. Major changes in National Flood Insurance Program (NFIP) policies and methodologies that have occurred since many of the previous coastal studies took place created the need to reflect more detailed and complete hazard information. Finally, thanks to more sophisticated mapping technologies and better data, FEMA can more accurately depict what today’s hazards look like for communities. As the map above shows, as of April 2017, much of the country has already received updated flood maps in the form of preliminary or effective FIRMs. 

Information about Coastal Flood Insurance Rate Maps (FIRMs)

  • Flood Insurance Rate Map (FIRM) is an official map on which FEMA has delineated Special Flood Hazard Area (SFHAs) applicable to the community. As part of its Risk MAP effort, FEMA scientists and engineers work with other Federal, State, regional, community, Tribal, non-profit, nongovernmental, and private-sector partners to determine the flood risk for properties along the populated U.S. coastline. If you live in a populated area along the coast, your community may have recently received, or may soon receive, an updated coastal FIRM and FIS report.
  • Within a coastal SFHA are two primary flood hazard zones: Zone VE and Zone AE. Zone VE, also known as a Coastal High Hazard Area, is considered one of the areas of highest risk depicted on FIRMs. Zone VE is designated where wave hazards are expected to be particularly strong and have the potential to cause dramatic structural damage. To address the added wave hazard, more stringent building practices are required in Zone VE, such as elevating a home on pilings so that waves can pass beneath it, or a prohibition to building on fill, which can be easily washed away by waves. These practices are intended to improve the chance of a home safely weathering a storm.
  • Base Flood Elevations (BFEs) will vary in each zone. Changes in flood zones and BFEs can have a significant impact on building requirements and flood insurance costs. BFEs may differ dramatically within a small area, because waves can diminish in size over a short distance upon encountering obstructions or steep ground. 
  • The coastal areas designated as Zone AE are places that experience lesser wave conditions during storm events, compared to Zone VE, or areas that are well sheltered from waves. Some Zone AE areas also have a Limit of Moderate Wave Action (LiMWA) shown on the FIRM; this is the location where the 1-percent-annual-chance wave height equals 1.5 feet. Past storms have shown that waves as small as 1.5 feet can cause foundation failure and structural damage to buildings. To communicate the high risk from waves that still exists in a portion of the Zone AE areas, FEMA began showing the LiMWA on FIRMs. Communities are encouraged to adopt building construction standards similar to Zone VE in those areas. For more on Coastal Zones and LiMWA, see the graphic below and click to watch the Coastal Zones/LiMWA Animation.

 VE – Wave height of 2-3 feet impacting the shoreline, sand beach, and unelevated buildings constructed below the 100-year still water elevation and before community entered NFIP. With a properly elevated buildings positioned above the flood level including wave effects, the graphic displays the building is protected from coastal flood zone risk. Coastal AE – Wave height of 3-1.5 feet impacting overland wind fetch and bordering on the vegetative (e.g., trees) region; AE – Wave height of less than 1.5 feet impacting the vegetation region; X – Indicates moderate risk and limited of base flooding and waves, or SFHA.
  • Flooding occurs not only in Special Flood Hazard Areas, such as Zones AE and VE, but also in areas with a low to moderate hazard, shown as Zone X on a FIRM. Anyone can be financially vulnerable to floods. People outside of high-risk areas file over 20% of National Flood Insurance Program claims and receive one third of FEMA’s disaster assistance for flooding.
  • Throughout the lifecycle of each coastal flood risk study, FEMA encourages community and public involvement and feedback. The regulatory requirements for coordination with community officials, including the appeal process, are documented in the Code of Federal Regulations at Title 44, Chapter I, Parts 66 and 67.
  • After a FIRM has been adopted, there are several processes available to revise or amend the map to accommodate map scale limitations or manmade or natural changes in floodplains. Contact your local Floodplain Administrator or a Map Specialist at the FEMA Map Information eXchange toll free, at 1‑877-FEMA MAP or by email at for more information. 

The Coastal Flood Risk Study Process

  • The coastal Flood Insurance Rate Map (FIRM) update process starts with the Discovery phase, during which FEMA meets with coastal communities, State representatives, and other stakeholders to share data and collaboratively determine needs and identify the best path forward.
  • A coastal FIRM update is generally conducted along the entire State coastline or across an entire lake basin (i.e., for the Great Lakes). This approach saves technical and data-gathering resources over the traditional county-by-county FIRM update approach. In addition to providing more accurate flood risk information, these studies make efficient use of tax dollars by generating new data that can be used to support other studies on coastal erosion, land-use planning, estuaries/wildlife habitat, and other coastal topics. Given the size and scope of these studies, a multitude of partners and communities work in cooperation toward a common goal. 
  • After a study is conducted, preliminary FIRMs and Flood Insurance Study (FIS) reports are distributed to each community involved. Information about the analysis used to create the new preliminary FIRMs is included in the FIS reports to provide transparency to the community and enable them to evaluate the technical approach and the science behind the study. To learn more about the steps involved in producing updated coastal flood risk information, please visit the Coastal Flood Risk Mapping Process page.
  • The FIRM is referred to as a "regulatory product” of the study, meaning that the FIRM is used to determine who must buy flood insurance and where floodplain development ordinances apply. Under the Risk MAP program, additional "non-regulatory” Flood Risk Products may also be included to help communities and property owners plan for resilience. Examples of Flood Risk Products include a coastal depth grid (which shows how deep the water would be during the 1-percent-annual-chance flood at any given location) and tools that identify the areas where the risk is greater than on the previous map, wave heights and severity of flooding, and erosion risk determinations.
  • After issuing the Preliminary FIRM, FEMA Regional Offices will usually hold formal coordination meetings with community officials and open houses for the public to explain changes to the FIRM, answer questions, and obtain feedback. Preliminary FIRMs are available for viewing online through FEMA’s Flood Map Service Center.
  • Afterward, a 90-day appeal period will be initiated. During this time, the community and others may appeal the proposed flood hazard information by submitting scientific or technical data that proves the flood hazard information shown on the preliminary FIRM and/or FIS report is erroneous. Please note that all comments or appeals to FIRMs should be submitted through the community; therefore, contact your community officials with any concerns. For additional information on FEMA's appeals process, please see the Changes to FEMA's Appeal Process Fact Sheet.
  • At the end of the 90-day appeal period or after all appeals have been resolved, FEMA will issue a Letter of Final Determination (LFD) establishing that the flood hazard information is final. The LFD initiates a 6-month compliance period during which the community must adopt or amend its floodplain management regulations to reflect the updated flood hazard information shown on the FIRM and FIS report.
  • The FIRM and FIS report will become effective following the 6-month compliance period. At that time, flood insurance will be required for structures that are shown on the FIRM in a Special Flood Hazard Area (SFHA) and carry a mortgage backed by a federally regulated lender. The final FIRM will be available at a community’s local map repository and online through FEMA’s Flood Map Service Center.
  • To learn about the progress of your community’s coastal mapping project, please visit the Risk MAP Progress website through Risk MAP webpage. This website offers an interactive map that allows users to zoom in, locate their community, and click to learn about the project status (i.e., timeframe for their preliminary and effective maps). A browser plug-in may be required to use this tool. If your community participates in the National Flood Insurance Program, paper copies of the FIRMs and FIS reports are on file at your local Community Map Repository, usually located in the planning and zoning office. Please contact a FEMA Map Information eXchange Map Specialist to determine the location of your Community Map Repository or to ask additional questions about a project status.

For More Information

Related Links

Last Updated: 
11/04/2019 - 07:36