Floodplain Definitions and Guidance

Floodplain Definitions and Guidance

 

Special Flood Hazard Area (SFHA)

Definition/Description for Kentucky

The land area covered by the floodwaters of the base flood is the SFHA on NFIP maps. The SFHA is the area where the (NFIP’s floodplain management regulations must be enforced and the area where the mandatory purchase of flood insurance applies. The SFHA includes Zones A, AO, AH, A1-30, AE, A99, AR, AR/A1-30, AR/AE, AR/AO, AR/AH, or AR/A.   

  • 59.1 – Definition of Lowest Floor
  • 60.3 – Floodplain Management Criteria

 

Floodway

Definition/Description

A “Regulatory Floodway” means 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. Communities must regulate development in these floodways to ensure that there are no increases in upstream flood elevations. For streams and other watercourses where FEMA has provided Base Flood Elevations (BFEs), but no floodway has been designated, the community must review floodplain development on a case-by-case basis to ensure that increases in water surface elevations do not occur, or identify the need to adopt a floodway if adequate information is available.

CFR 60.0 – Criteria for Land Management and Use and  Floodplain management criteria for floodprone areas

  • 60.3 (c) (10) – Cumulative Effects of Development
  • 60.3 (d) (2) – Floodway Adoption
  • 60.3 (d) (3) – Floodway Encroachment
  • 60.3 (d) (4) – Floodway Encroachments that Cause an Increase

 

Encroachment / NFIP Requirement

Definition/Description

Encroachments are activities or construction within the floodway including fill, new construction, substantial improvements, and other development. These activities are prohibited within the adopted regulatory floodway unless it has been demonstrated through hydrologic and hydraulic analyses that the proposed encroachment would not result in any increase in flood levels.  The community is responsible to review and maintain record of the documentation demonstrating that any permitted floodway encroachment meets NFIP requirements. A “no-rise certification” for floodways may be used to document the analyses.

 

Fill

Definition/Description

Earthen fill is sometimes placed in an SFHA to reduce flood risk to the filled area. The placement of fill is considered development and will require a permit under applicable Federal, state and local laws, ordinances, and regulations. Fill is prohibited within the floodway unless it has been demonstrated that it will not result in any increase in flood levels. Some communities limit the use of fill in the flood fringe to protect storage capacity or require compensatory storage.

 

Compensatory Storage

Definition/Description

The NFIP floodway standard in 44 CFR 60.3 (d) restricts new development from obstructing the flow of water and increasing flood heights. However, this provision does not address the need to maintain flood storage. Especially in flat areas, the floodplain provides a valuable function by storing floodwaters. When fill or buildings are placed in the flood fringe, the flood storage areas are lost and flood heights will go up because there is less room for the floodwaters. This is particularly important in smaller watersheds which respond sooner to changes in the topography. One approach that may be used to address this issue is to require compensatory storage to offset any loss of flood storage capacity. Some communities adopt more restrictive standards that regulate the amount of fill or buildings that can displace floodwater in the flood fringe. Community Rating System (CRS)  credits are available for communities that adopt compensatory storage requirements.

 

Higher Standard

Definition/Description

FEMA has established minimum floodplain management requirements for communities participating in the NFIP. Communities must also enforce any more restrictive State requirements. Any community may exceed the minimum standards by adopting more comprehensive floodplain management regulations. In some instances, community officials may have access to information or knowledge of conditions that require, particularly for human safety, higher standards than the minimum NFIP criteria. Any floodplain management regulations adopted by a state or community which are more restrictive than the criteria set forth in the NFIP regulations are encouraged and shall take precedence. Communities that exceed the minimum requirements of the NFIP may be eligible to participate in the Community Rating System (CRS).

 

 

 

 

 

 

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