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Acronyms and Terms

For more information on flood related acronyms and definitions visit:


BFE - Base Flood Elevation
CRS - Community Rating System
DFIRM - Digital Flood Insurance Rate Map
DMA - Disaster Mitigation Act of 2000
E.O. - Executive Order
EOC - Emergency Operations Center
FEMA - Federal Emergency Management Agency
FIMA - Federal Insurance & Mitigation Administration
FIRM - Flood Insurance Rate Map
FIS - Flood Insurance Study
FMA - Flood Mitigation Assistance
FPMP - Floodplain Management Plan
GIS - Geographic Information System
HMGP - Hazard Mitigation Grant Program
ICC - Increased Cost of Compliance
KDOW - Kentucky Division of Water
LOJIC - Louisville and Jefferson County Information Consortium
LOMA - Letter of Map Amendment
LOMC - Letter of Map Change
LOMR - Letter of Map Revision
LOMR-F - Letter of Map Revision based on Fill
LRCZ - Local Regulatory Conveyance Zone
MOE - Minimum Opening Elevation
NFIP - National Flood Insurance Program
SFHA - Special Flood Hazard Area


Administering Agency: The agency responsible for maintaining and enforcing floodplain related ordinances. For Louisville and Jefferson County, Kentucky, it is MSD.

Allowable surcharge: The acceptable limit of increased flood elevation in the floodway due to obstruction of the floodway fringe.

Base flood: The flood having a 1% chance of being equaled or exceeded in any given year, also known as the “100-year” or “1% chance” flood. The base flood is a statistical concept used to ensure that all properties subject to the NFIP are protected to the same degree against flooding.

Base flood elevation: (BFE): The elevation of the crest of the base or 100-year flood.

Building: As used by the Community Rating System (CRS), the term is the same as “structure” in the NFIP regulations (44 CFR 59.1). For CRS purposes, a building is a structure that is walled and roofed, principally above ground and permanently affixed to a site. The term includes a manufactured (mobile) home on a permanent foundation (such as a poured masonry slab, foundation walls, piers, or block supports) so that no weight is carried by the wheels or axles. “Walled and roofed” means that a building has two or more rigid exterior walls in place and is adequately anchored so that it will resist flotation, collapse, and lateral movement. “Principally above ground” means that at least 51% of the actual cash value of the building, including equipment and machinery that are part of the building, is above ground.

Contour: A line of equal elevation on a topographic (contour) map.

Critical facilities:

  • Structures or facilities that produce, use or store highly volatile, flammable, explosive, toxic and/or water-reactive materials;
  • Hospitals, nursing homes, and housing likely to contain occupants who may be sufficiently mobile to avoid death or injury during a flood;
  • Police stations, fire stations, vehicle and equipment storage facilities, and emergency operations centers that are needed for flood response activities before, during, and after a flood; and
  • Public and private utility facilities that are vital to maintaining or restoring normal services to flooded areas before, during and after a flood.

CRS Classification: A rating of a community’s floodplain management program according to the CRS Schedule. For more information, please review the CRS summary provided.

CRS Coordinator: A local official designated by the Chief Executive Officer of the community to coordinate the community’s CRS application and verification.

Datum: A reference surface used to ensure that all elevation records are properly related. Many communities have their own datum, which is developed before there was a national standard. The NFIP uses the National Geodetic Vertical Datum (NGVD), which is in relation to mean sea level. The FIRM indicates the datum that applies to the community.

Development: Any human-caused change to improved or unimproved real estate including, but not limited to, buildings or other structures, mining, dredging, filling, grading, paving, excavation, or drilling operations.

Discharge: The amount of water that passes a point in a given period of time. Rate of discharge is usually measured in cubic feet per second (cfs).

Elevated Building: A building that has been raised to an elevation at least one foot above the BFE recorded for that area.

Flood: A general and temporary condition of partial of complete inundation of normally dry land areas from either the overflow of inland waters or the unusual and rapid accumulation or runoff of surface waters from any source.

Flood Insurance Rate Map (FIRM): An official map of a community, on which the FIA has delineated both the SFHA’s and the risk premium zones applicable to the community. Most FIRM’s include detailed floodplain mapping for some or all of a community’s floodplains. In most cases, the date of the first FIRM issued to a community is the date the community entered the Regular Program of the National Flood Insurance Program.

Flood Insurance Study (FIS): A report by the FIA for a community in conjunction with the community’s FIRM. The study contains such background data as the base flood discharges and water surface elevations that were used to prepare the FIRM. In most cases, a community FIRM with detailed mapping will have corresponding flooding insurance study.

Floodplain: Any land area susceptible to being inundated by floodwaters from any source. A FIRM identifies most, but not necessarily all, of a community’s floodplain as a SFHA.

Floodplain Board: The entity responsible for reviewing requested variances from the floodplain ordinance. For Louisville Metro the Floodplain Board is the MSD Board.

Floodplain Permit: Required document to develop within the Local Regulatory Floodplain of Jefferson County.

Floodplain Storage Compensation: An artificially excavated, hydraulically equivalent volume of floodplain storage sufficient to offset a reduction in floodplain storage resulting from filling or construction within the local regulatory floodplain. Such floodplain storage compensation shall be within the same watershed and shall be provided on the same property or at an alternate site if the administering agency so approves.

Floodproofing: Protective measures added to or incorporated in a building that is not elevated above the BFE to prevent or minimize flood damage. “Dry floodproofing” measures are designed to keep water from entering a building. “Wet floodproofing” measures minimize damage to a structure and its contents from water that is allowed into a building. (See Retrofitting)

Floodway: The channel of a river and the portion of the overbank floodplain that carries most of the base flood. The floodway must be kept open so that floods can proceed downstream and not be obstructed or diverted onto other properties. The NFIP regulations allow construction in the floodway provided that it does not obstruct flood flows or increase flood heights.

Flood Fringe: The portion of the floodplain lying on either side of the floodway.

Freeboard: A margin of safety added to the BFE to account for waves, debris, miscalculations, or lack of data.

Fully Developed Watershed: A condition of a watershed that most accurately reflects the ultimate land use of the watershed and its potential to cause runoff.

Geographic Information System (GIS): A computer system capable of assembling, storing, manipulating, and displaying geographically referenced information, i.e. data identified according to their locations.

Hydrology: The science dealing with the waters of the earth. A flood discharge is developed by a hydrologic study.

Increased Cost of Compliance (ICC): a flood insurance claim provision that helps fund the cost of bringing a flood-damaged building into compliance with floodplain management standards.

Local Regulatory Conveyance Zone (LRCZ): The channel of a river or solid blue line stream and the land adjacent to that river or stream which if unobstructed will discharge a local regulatory flood without cumulatively increasing the water surface elevation more than one tenth of one foot. The conveyance zone is determined by an equal loss of conveyance (at higher elevation) occurring on each side of the channel.

Local Regulatory Flood: The flood having a one-percent (1%) likelihood of being equaled or exceeded in any given year based on a fully developed watershed.

Local Regulatory Floodplain: Any stream course or normally dry land area susceptible to being partially or completely inundated by the overflow of water from sources of public water or by the unusual and rapid accumulations or runoff of public surface waters and subject to a local regulatory flood.

Lowest Adjacent Grade: The lowest natural elevation of the ground surface, prior to construction, next to the proposed walls of a building.

Natural and beneficial functions of floodplains:
a. The functions associated with the natural or relatively undisturbed floodplain that moderate flooding, retain waters, reduce erosion and sedimentation, and mitigate the effects of waves and surges from storms; and
b. Ancillary beneficial functions, including maintenance of water quality, recharge of ground water and provision of fish and wildlife habitat.

New Construction: Any development which had not begun construction on the effective date of this ordinance. The first placement of permanent features of the development such as pouring of slabs or footings and installation of piles constitute beginning of construction but land preparation, grading and filling or construction of accessory structures do not.

Ponding: A flooding condition in flat areas caused when rain runoff drains to a location that has an insufficient opportunity to drain. Ponding water usually stands until it evaporates, seeps into the ground, or is pumped out.

Post-FIRM building: For insurance rating purposes, a post-FIRM building was constructed or substantially improved after December 31, 1974, or after the effective date of the initial FIRM of a community, whichever is later. A post-FIRM building is required to meet the NFIP’s minimum Regular Program flood protection standards.

Pre-FIRM building: For insurance rating purposes, a pre-FIRM building was constructed or substantially improved before December 31, 1974, or before the effective date of the initial FIRM of a community, whichever is later. Most pre-FIRM buildings were constructed without taking the flood hazard into account.

Public Water: Water that flows from more than one property or from public lands or rights-of-way.

Regulatory floodplain: For purposes of the CRS, the floodplain that is regulated by a community, including the SFHA. It covers a larger area in communities that regulate development in flood problem areas outside the SFHA as mapped by the Federal Insurance Administration.

Repetitive loss property: For purposes of the CRS, a property for which two or more NFIP losses of at least $1,000 each have been paid within any 10-year rolling period since 1978.

Retrofitting: Retrofitting techniques include floodproofing, elevation, construction of small levees, and other modifications made to an existing building or its yard to protect it from flood damage (see floodproofing).

Riverine Flooding: Flooding of or produced by a river. Riverine floodplains have readily identifiable channels. Floodway maps can only be prepared for riverine floodplains.

Sensitive area: An area defined by state or local regulations as deserving special protection because of unique features or its value as habitat for a wide range of species of flora and fauna. A sensitive area is subject to more restrictive development regulations than other floodplains or wetlands. Although sensitive areas are often closely associated with a body of water, they may extend beyond the SFHA.

Sheet Flow: A condition of flooding where there is moving water but no identifiable channel. Flooding depths are usually shallow (less than 3 feet). Sheet flow may have a high velocity, as on alluvial fans.

Special Flood Hazard Area, (SFHA): The base floodplain delineated on a FIRM. The SFHA is mapped as a Zone A (see definition). The SFHA may or may not encompass all of a community’s flood problems.

Substantial Damage: Damage of any origin sustained by a building whereby the cost of restoring the building to its before-damage condition would equal or exceed 50% of the market value of the building before the damage occurred.

Substantial Improvement: Any reconstruction, rehabilitation, addition, or other improvement to a building, the cost of which equals or exceeds 50% of the market value of the building before the start of construction of the improvement.
“any combination of repairs, reconstruction, alteration, additions to or improvements to existing development, taking place during the life of the structure and begun after the effective date of the this ordinance in which cumulative cost equals or exceeds fifty percent (50%) of the market value of the structure. The market value of the structure for purposes of this ordinance is (a) the appraised value of the structure determined by a certified general real property appraiser licensed and certified by the Kentucky Real Estate Appraisers Board or lacking that, the current assessment of the structure shown by the Property Valuation Administrator of Jefferson County, prior to start of the initial addition, repair or improvement, or (b) in the case of damage, prior to the damage’s occurrence. The term includes repairs made to structures which have incurred damage equal to or in excess of fifty percent (50%) of the pre-damage value of the structure, regardless of the cumulative cost of the actual repair work performed. The cost of alteration, additions, or improvements shall reflect the value in the marketplace of the labor and materials to be used in the improvements. The first alteration of any wall, ceiling floor or other structural part of the structure constitutes beginning of construction of the substantial improvement. The term does not include the cost of floodproofing or elevating a structure or any portion thereof above the local regulatory base flood elevation plus one foot.”

Surcharge: An increase in flood elevation due to obstruction of the floodplain that reduces its conveyance capacity.

Watershed: All the area within a geographic boundary from which water, sediments and other transportable materials, and dissolved materials drain or are carried by water to a common outlet, such as a point on a larger stream, lake or underlying aquifer.

Zone A: The SFHA (except coastal V Zones) shown on a community’s FIRM. There are seven types of A Zones:

  • A: SFHA where no BFE is provided.
  • A#: Numbered A Zones (e.g., A7 or A14), SFHA where the FIRM shows a BFE in relation to NGVD.
  • AE: SFHA where BFEs are provided. AE Zone delineations are now used on new FIRMs instead of A# Zones.

Zone B: Area of moderate flood hazard, usually depicted on FIRMs as between the limits of the base and 500-year floods of the primary source of flooding. B Zones may have local, shallow flooding problems. B Zones are also used to designate areas protected by levees and base floodplains of little hazard, such as those with average depths of less than 1 foot.

Zone C: Area of minimal flood hazard, usually depicted on FIRMs as above the 500-year flood level of the primary source of flooding. C Zones may have local, shallow flooding problems. B and C Zones may have flooding that does not meet the criteria to be mapped as a SFHA, especially ponding and local drainage problems.

Zone D: Area of undetermined but possible flood hazard.

Zone X: Newer FIRMs show Zones B and C (see above) as Zone X. The shaded Zone X corresponds to a Zone B and the unshaded Zone X corresponds to a Zone C.

Last Updated: February 28, 2012

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