DDOE: Floodplain FAQ

2. What is a floodplain?

A floodplain is any land area susceptible to being inundated by flood waters from any source. In general, a floodplain is the flat area located adjacent to the main stream channel. When stream banks overflow during or after a storm, the floodplain provides natural storage for the excess water.

3. What is a FIRM?

A FIRM or Flood Insurance Rate Map is an official map of a community on which the Federal Emergency Management Agency has delineated both the Special Flood Hazard Areas and the risk premium zones applicable to the community.

4. What is a FIS?

A FIS or Flood Insurance Study is a report published by FEMA for a community issued along with the community's Flood Insurance Rate Map (FIRM). The study contains such background data as the base flood discharges and water surface elevations that were used to prepare the FIRM. The flood map (FIRM) and flood study (FIS) also show projected flood elevations, flood velocities, floodway dimensions, insurance rating zones, and descriptions of how the study was conducted and how the maps were prepared. This information is needed for rating flood insurance, regulating floodplain development and carrying out other floodplain management measures.

5. What is a Special Flood Hazard Area (SFHA)?

A Special Flood Hazard Area (SFHA) is a high-risk area defined as any land that would be inundated by a flood having a 1-percent chance of occurring in any given year (also referred to as the base flood and 100-year flood) displayed on FEMA maps (i.e. FIRM).

6. What is a regulatory floodway and who designates it?

The regulatory floodway, which is adopted into the community's floodplain management ordinance (Flood Hazard Rules in the District of Columbia), is the stream channel plus that portion of the overbanks that must be kept free from encroachment in order to discharge the 1-percent-annual-chance flood without increasing flood levels by more than 1.0 foot. The intention of the floodway is not to preclude development. Rather, it is intended to assist communities in prudently and soundly managing floodplain development and to prevent additional damages to other property owners. The community is responsible for prohibiting encroachments, including fill, new construction, and substantial improvements, within the floodway unless it has been demonstrated through hydrologic and hydraulic analyses that the proposed encroachment will not increase flood levels within the community. In areas that fall within the 1-percent-annual-chance floodplain, but are outside the floodway (termed the "floodway fringe"), development will, by definition, cause no more than 1.0-foot increase in the 1-percent-annual-chance water surface elevation.

7. What are Flood Hazard Zones?

And what is a definition of a flood zone designation? Several areas of flood hazard are commonly identified on the FIRM. One of these areas is the SFHA. SFHAs are labeled as:

Zone A	Zone A1-30	Zone AR	Zone AR/AO	Zone V
Zone AO	Zone AE	Zone AR/AE	Zone AR/A1-30	Zone VE
Zone AH	Zone 99	Zone AR/AH	Zone AR/A	Zone V1-V30

Moderate flood hazard areas, labeled Zone B or Zone X (shaded), are also shown on the FIRM, and the areas between the limits of the base flood and the 0.2-percent-annual-chance flood. The areas of minimal flood hazard, which are the areas outside the SFHA and higher than there elevation of the 0.2-percent-annual-chance flood, are labeled Zone C or Zone X (unshaded). The definitions for the common flood hazard areas are presented below:

Zone A: Areas subject to inundation by the 1-percent-annual-chance flood event. Because detailed hydraulic analyses have not been performed, no base flood elevation or depths are shown. Mandatory flood insurance purchase requirements apply.

Zones AE and A1-A30: Areas subject to inundation by the 1-percent-annual-chance flood event determined by detailed methods. Base flood elevations area shown within these zones. Mandatory flood insurance purchase requirements apply. (Zone AE is used on new and revised maps in place of Zones A1-A30.)

Zones B, C, and X: Areas identified in the community Flood Insurance Study (FIS) as areas of moderate or minimal hazard from the principal source of flood in the area. However, buildings in these zones could be flooded by severe, concentrated rainfall couples with inadequate local drainage systems. Local stormwater drainage systems are not normally considered in the community's FIS. The failure of a local drainage system creates areas of high flood risk within these rate zones. Flood insurance is available in participating communities but is not required by regulation in these zones. (Zone X is used on new and revised maps in place of Zones B and C.)

8. What procedures are available for changing or correcting a Flood Insurance Rate Map (FIRM)?

FEMA has established administrative procedures for changing effective FIRMs and FIS reports based on new or revised scientific or technical data. A physical change to the affected FIRM panels and portions of the FIS report is referred to as a "Physical Map Revision," or "PMR." Changes can also be made by a Letter of Map Change (LOMC). The three LOMC categories are Letter of Map Amendment (LOMA), Letter of Map Revision Based on Fill (LOMR-F), and Letter of Map Revision (LOMR).

9. What is a Letter of Map Amendment (LOMA)?

A LOMA is an official revision by letter to an effective FIRM. A LOMA results from an administrative procedure that involves the review of scientific or technical data submitted by the owner or lessee of property who believes the property has incorrectly been included in a designated SFHA. A LOMA amends the currently effective FEMA map and establishes that as specific property is not located in an SFHA.

10. What is a Letter of Map Revision (LOMR)?

A LOMR is an official revision to the currently effective FIRM. It is used to change flood zones, floodplain and floodway delineations, flood elevations, and planimetric features. All requests for LOMRs should be made to FEMA through the chief executive officer of the community, since it is the community that must adopt any changes and revisions to the map. If the request of a LOMR is not submitted through the chief of executive officer of the community, evidence must be submitted that the community has been notified of the request.

11. What is a Letter of Map Revision Based on Fill (LOMR-F)?

A LOMR-F is an official revision by letter to an effective FIRM. A LOMR-F states FEMA's determination concerning whether a structure or parcel has been elevated on fill above the base flood elevation and is, therefore, excluded from the SFHA.

12. What is a Conditional Letter of Map Revision (CLOMR)?

A Conditional Letter of Map Revision (CLOMR) is FEMA's formal review and comment as to whether a proposed project complies with the minimum NFIP floodplain management criteria. If it is determined that it does, the CLOMR also described any eventual revisions that will be made to the NFIP maps upon completion of the project.

13. What is the role of the community in floodplain management?

When the community like the District of Columbia chooses to join the NFIP, it must adopt and enforce minimum floodplain management standards for participation. FEMA works closely with State and local officials to identify flood hazard areas and flood risk. The floodplain management requirements within the SFHA are designated to prevent new development from increasing the flood threat and to protect new and existing buildings from anticipated flood events. When a community like the District of Columbia chooses to join the NFIP, it must require permits for all development in the SFHA and ensure that construction materials and methods used will minimize future flood damage. Permit files must contain documentation to substantiate how buildings were actually constructed. In return, the Federal Government makes flood insurance available for almost every building and its contents within the community. Communities must ensure that their adopted floodplain management ordinance and enforcement procedures meet program requirements. Local regulations must be updated when additional data are provided by FEMA or when Federal or State standards are revised.

14. What constitutes "Substantial Improvement" or "Substantial Damage"?

"Substantial improvement" means any rehabilitation, addition, or other improvement of a building when the cost of the improvement equals or exceeds 50 percent of the market value of the building before start of construction of the improvement. The term includes buildings that have incurred "substantial damage." "Substantial damage" means damage of any origin sustained by a building when the cost of restoring the building to its pre-damaged condition would equal or exceed 50 percent of the market value of the building before the damage occurred. Substantial damage is determined regardless of the actual repair work performed.