FEMA Floodplain Rules and Federal Dam Safety Context for Ponds

Key points

• DefinitionUnder the National Flood Insurance Program (NFIP) regulations, "development" means any man-made 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, or storage of equipment or materials. Excavation, filling, grading and dredging, the earthwork used to dig a pond or build an embankment, are all named in the definition.

  Applies when: Any NFIP floodplain question; the NFIP permit requirements attach to "development" 44 CFR 59.1 ("Development") [1]
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  Development means any man-made 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 or storage of equipment or materials.

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• DefinitionThe "area of special flood hazard" is the land in the flood plain within a community subject to a 1 percent or greater chance of flooding in any given year. It may be shown as Zone A on a Flood Hazard Boundary Map and is usually refined on the Flood Insurance Rate Map (FIRM) into Zones A, AO, AH, A1-30, AE, A99, AR (and AR combinations), VO, V1-30, VE or V. "Special flood hazard area" (SFHA) means the same thing.

  44 CFR 59.1 ("Area of special flood hazard"; "Special flood hazard area") [1]
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  Area of special flood hazard is the land in the flood plain within a community subject to a 1 percent or greater chance of flooding in any given year. The area may be designated as Zone A on the FHBM. After detailed ratemaking has been completed in preparation for publication of the flood insurance rate map, Zone A usually is refined into Zones A, AO, AH, A1-30, AE, A99, AR, AR/A1-30, AR/AE, AR/AO, AR/AH, AR/A, VO, or V1-30, VE, or V. For purposes of these regulations, the term "special flood hazard area" is synonymous in meaning with the phrase "area of special flood hazard".

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• RequirementFEMA guidance: a permit is required before construction or development begins within any Special Flood Hazard Area. Where FEMA has not defined the SFHA, the community must require permits for all proposed construction or other development. Permits make sure projects meet NFIP requirements and the community's floodplain management ordinance.

  Applies when: Pond excavation, embankment, fill or grading on land inside a mapped Special Flood Hazard Area in a community that participates in the NFIP FEMA, "Permit for Floodplain Development" (glossary; citing 44 CFR 60.3(a)(1), (a)(3)) [2]
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  A permit is required before construction or development begins within any Special Flood Hazard Area (SFHA). If FEMA has not defined the SFHA within a community, the community shall require permits for all proposed construction or other development in the community including the placement of manufactured homes, so that it may determine whether such construction or other development is proposed within flood-prone areas. Permits are required to ensure that proposed development projects meet the requirements of the NFIP and the community's floodplain management ordinance.

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• RequirementWhere FEMA has not defined the special flood hazard areas in a community, has not provided water surface elevation data, and has not provided sufficient data to identify the floodway, but the community has applied to participate in the NFIP, the community must require permits for all proposed construction or other development anywhere in the community, so that it can determine whether the work is proposed within flood-prone areas.

  Applies when: NFIP applicant community for which FEMA has not yet defined special flood hazard areas or provided flood elevation or floodway data 44 CFR 60.3(a)(1) [6]
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  (a) When the Federal Insurance Administrator has not defined the special flood hazard areas within a community, has not provided water surface elevation data, and has not provided sufficient data to identify the floodway...but the community has indicated the presence of such hazards by submitting an application to participate in the Program, the community shall: (1) Require permits for all proposed construction or other development in the community...so that it may determine whether such construction or other development is proposed within flood-prone areas

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• Definition"Flood plain management regulations" are the State or local zoning ordinances, subdivision regulations, building codes, health regulations, special purpose ordinances (such as a flood plain ordinance, grading ordinance and erosion control ordinance) and other applications of police power that provide standards for flood damage prevention and reduction, in any combination. The local floodplain permit may therefore sit in a zoning, grading or special floodplain ordinance.

  44 CFR 59.1 ("Flood plain management regulations") [1]
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  Flood plain management regulations means zoning ordinances, subdivision regulations, building codes, health regulations, special purpose ordinances (such as a flood plain ordinance, grading ordinance and erosion control ordinance) and other applications of police power. The term describes such state or local regulations, in any combination thereof, which provide standards for the purpose of flood damage prevention and reduction.

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• RequirementThe Part 60 criteria are minimum standards. Any community may exceed them, and flood plain management regulations adopted by a State or a community that are more restrictive than the Federal criteria are encouraged and take precedence. State and local rules may therefore be stricter than the Federal minimums described here.

  44 CFR 60.1(d) [6]
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  The criteria set forth in this subpart are minimum standards for the adoption of flood plain management regulations by flood-prone, mudslide (i.e., mudflow)-prone and flood-related erosion-prone communities. Any community may exceed the minimum criteria under this part....any flood plain management regulations adopted by a State or a community which are more restrictive than the criteria set forth in this part are encouraged and shall take precedence.

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• Size cutoffWhere FEMA has published base flood elevations in Zones A1-30 and AE but no regulatory floodway has been designated, no new construction, substantial improvement, or other development (including fill) may be permitted in those zones unless it is demonstrated that the cumulative effect of the proposed development, combined with all other existing and anticipated development, will not raise the base flood water surface elevation more than one foot at any point within the community.

  Applies when: Fill, embankment or other development in Zones A1-30/AE with base flood elevations but no designated floodway 44 CFR 60.3(c)(10) [6]
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  (10) Require until a regulatory floodway is designated, that no new construction, substantial improvements, or other development (including fill) shall be permitted within Zones A1-30 and AE on the community's FIRM, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one foot at any point within the community.

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• RequirementFloodway "no-rise" rule: the community must prohibit encroachments within the adopted regulatory floodway, including fill, new construction, substantial improvements and other development, unless hydrologic and hydraulic analyses performed in accordance with standard engineering practice show that the proposed encroachment would not result in any increase in flood levels within the community during the base flood discharge.

  Applies when: Any pond embankment, spoil placement, fill or other development inside a mapped regulatory floodway 44 CFR 60.3(d)(3) [6]
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  (3) Prohibit encroachments, including fill, new construction, substantial improvements, and other development within the adopted regulatory floodway unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels within the community during the occurrence of the base flood discharge;

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• ProcessA community may approve development in Zones A1-30, AE and AH that would raise the base flood elevation by more than one foot only if the community first applies for a conditional FIRM revision, meets the requirements of 44 CFR 65.12, and receives FEMA approval.

  Applies when: A dam, embankment or fill that would raise base flood elevations by more than 1 foot where no floodway is designated 44 CFR 60.3(c)(13) [6]
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  (13) Notwithstanding any other provisions of § 60.3, a community may approve certain development in Zones Al-30, AE, and AH, on the community's FIRM which increase the water surface elevation of the base flood by more than one foot, provided that the community first applies for a conditional FIRM revision, fulfills the requirements for such a revision as established under the provisions of § 65.12, and receives the approval of the Federal Insurance Administrator.

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• ProcessNotwithstanding the no-rise rule, a community may permit floodway encroachments that would increase base flood elevations only if it first applies for a conditional FIRM and floodway revision, meets the requirements of 44 CFR 65.12, and receives FEMA approval.

  Applies when: A dam or fill in a regulatory floodway that cannot meet the no-rise standard 44 CFR 60.3(d)(4) [6]
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  (4) Notwithstanding any other provisions of § 60.3, a community may permit encroachments within the adopted regulatory floodway that would result in an increase in base flood elevations, provided that the community first applies for a conditional FIRM and floodway revision, fulfills the requirements for such revisions as established under the provisions of § 65.12, and receives the approval of the Federal Insurance Administrator.

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• ProcessA community, or an individual through the community, may ask FEMA to comment on whether a proposed project, if built as proposed, would justify a map revision; FEMA's response is a Conditional Letter of Map Revision (CLOMR). The supporting data are the same as for final revisions under 65.5-65.7, except that as-built certification is not required. Map revisions themselves cannot be based on proposed projects or future conditions, which is why conditional approval is sought before construction.

  Applies when: A proposed dam, embankment or fill that would change the floodway, base flood elevations or SFHA 44 CFR 65.8; 65.6(a)(3) [9]
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  (3) Revisions cannot be made based on the effects of proposed projects or future conditions....A community, or an individual through the community, may request FEMA's comments on whether a proposed project, if built as proposed, would justify a map revision. FEMA's comments will be issued in the form of a letter, termed a Conditional Letter of Map Revision, in accordance with 44 CFR part 72. The data required to support such requests are the same as those required for final revisions under §§ 65.5, 65.6, and 65.7, except as-built certification is not required.

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• ProcessRequests to change an effective map, other than changes FEMA initiates, must be made in writing by the community's Chief Executive Officer or an official the CEO designates. If the CEO refuses to submit a request on behalf of another party, FEMA will review it only with written evidence that the CEO or designee was asked to submit it.

  44 CFR 65.4(b) [9]
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  (b) All requests for changes to effective maps, other than those initiatedby FEMA, must be made in writing by the Chief Executive Officer of the community (CEO) or an official designated by the CEO. Should the CEO refuse to submit such a request on behalf of another party, FEMA will agree to review it only if written evidence is provided indicating the CEO or designee has been requested to do so.

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• ProcessBase flood elevations can go up or down because of physical changes affecting flooding conditions. As soon as practicable, and no later than six months after the information becomes available, the community must notify FEMA of the changes by submitting technical or scientific data under Part 65.

  Applies when: A completed dam, embankment, channel change or fill that changes base flood elevations 44 CFR 65.3 [9]
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  A community's base flood elevations may increase or decrease resulting from physical changes affecting flooding conditions. As soon as practicable, but not later than six months after the date such information becomes available, a community shall notify the Administrator of the changes by submitting technical or scientific data in accordance with this part.

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• Size cutoffNational Inventory of Dams inclusion criteria (context only, not a permit): the NID documents dams that are (1) high hazard potential (failure or mis-operation likely to result in loss of human life); (2) significant hazard potential (failure or mis-operation likely to disrupt access to critical facilities, damage public and private facilities, and require difficult mitigation); or (3) dams that meet minimum height and reservoir size: at least 25 feet high with more than 15 acre-feet of storage, or at least 50 acre-feet of storage with more than 6 feet of height. The NID does not yet contain all U.S. dams that meet these criteria.

  Applies when: Context for embankment ponds; NID listing is informational, not a permit USACE, National Inventory of Dams, "Mission & History" [11]
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  Dams where a failure or mis-operation will likely result in loss of human life (high hazard potential). Dams where a failure or mis-operation would likely result in disruption of access to critical facilities, damage to public and private facilities, and require difficult mitigation efforts (significant hazard potential)....these dams are equal to or exceed 25 feet in height and exceed 15 acre-feet in storage, or equal to or exceeding 50 acre-feet in storage and exceeding 6 feet in height. The NID does not yet contain all dams in the U.S. that meet these criteria.

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• AgencyUSACE: most dams in the National Inventory of Dams are regulated by State agencies through construction permits, inspections and/or enforcement, and Federal agencies own or regulate five percent of the dams in the NID.

  USACE, National Inventory of Dams, "Mission & History" [11]
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  Most dams in the NID are regulated by the state agencies through construction permits, inspections, and/or enforcement. The federal agencies own or regulate five percent of the dams in the NID.

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The local floodplain permit and what it checks

Where FEMA has mapped Zone A but has neither produced base flood elevations nor identified a floodway, the community must require permits for all proposed construction and other development within Zone A. There, the community must require that all new subdivision proposals and other proposed developments greater than 50 lots or 5 acres, whichever is less, include base flood elevation data, and the community must obtain, review and reasonably use any base flood elevation and floodway data available from a Federal, State or other source as criteria for requiring that development meet listed 60.3 standards, including the floodway standards. [6]

FEMA's study guide for local officials (guidance, not regulation; the PDF was created in January 2005, modified in May 2006 and is still referenced on FEMA's local officials page) says a permit is required for all development in the SFHA shown on the FIRM and lists excavation, filling, land clearing and grading among the activities that count as development. It says communities have some discretion to exempt obviously insignificant activities such as planting a garden, farming, putting up a mailbox or erecting a flagpole, the key being whether a project will present a new obstruction to flood flows, alter drainage or have the potential to be a substantial improvement. It adds that a community may be able to exempt projects valued at less than, say, $500, but that suggestion is limited to projects "other than filling, grading or excavating." [14]

The same study guide says 44 CFR 60.3(a)(2), the permit-review duty described above, requires all NFIP communities to ensure that other Federal and State permits have been obtained, and advises communities not to issue the local permit until they are certain the other agencies' requirements are met. It notes that some communities issue the local permit on the condition that the other permits are obtained, but calls that less effective than holding the permit until the applicant shows the other agencies have issued or will issue theirs. [6][14]

In riverine situations, before any alteration or relocation of a watercourse the community must notify adjacent communities and the State Coordinating Office, send copies of the notices to FEMA, and ensure that the flood carrying capacity of the altered or relocated portion is maintained. [6]

A structure or other development that lacks the elevation certificate, other certifications or other evidence of compliance required by listed parts of 44 CFR 60.3, which include the encroachment analyses for fill and other development under 60.3(c)(10) and in floodways under 60.3(d)(3), is presumed to be in violation until that documentation is provided. [1]

• RequirementWhere FEMA has mapped A zones (SFHAs) on the community's FHBM or FIRM but has not produced base flood elevations or a floodway, the community must require permits for all proposed construction and other developments within Zone A and apply the review standards of 60.3(a)(2)-(6) to that development.

  Applies when: Development in an unnumbered Zone A (no base flood elevations published) 44 CFR 60.3(b)(1)-(2) [6]
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  (b) When the Federal Insurance Administrator has designated areas of special flood hazards (A zones) by the publication of a community's FHBM or FIRM, but has neither produced water surface elevation data nor identified a floodway or coastal high hazard area, the community shall: (1) Require permits for all proposed construction and other developments including the placement of manufactured homes, within Zone A on the community's FHBM or FIRM; (2) Require the application of the standards in paragraphs (a) (2), (3), (4), (5) and (6) of this section

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• Size cutoffIn Zone A areas without published base flood elevations, the community must require that all new subdivision proposals and other proposed developments greater than 50 lots or 5 acres, whichever is less, include base flood elevation data. The community must also obtain, review and reasonably use any base flood elevation and floodway data available from a Federal, State or other source as criteria for requiring that new construction, substantial improvements or other development in Zone A meet listed 60.3 standards, including the floodway standards in 60.3(d)(2) and (d)(3).

  Applies when: Development proposals in Zone A without base flood elevations 44 CFR 60.3(b)(3)-(4) [6]
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  (3) Require that all new subdivision proposals and other proposed developments...greater than 50 lots or 5 acres, whichever is the lesser, include within such proposals base flood elevation data; (4) Obtain, review and reasonably utilize any base flood elevation and floodway data available from a Federal, State, or other source...as criteria for requiring that new construction, substantial improvements, or other development in Zone A on the community's FHBM or FIRM meet the standards in paragraphs (c)(2), (c)(3), (c)(5), (c)(6), (c)(12), (c)(14), (d)(2) and (d)(3) of this section

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• RequirementAn NFIP community must review proposed development (all development in a community without mapped flood zones; development within the mapped special flood hazard area zones once FEMA has mapped them) to make sure that all necessary permits have been received from the governmental agencies whose approval is required by Federal or State law, including section 404 of the Clean Water Act.

  Applies when: Pond excavation, embankment, fill or grading on land inside a mapped Special Flood Hazard Area in a community that participates in the NFIP 44 CFR 60.3(a)(2) (applied to Zone A by 60.3(b)(2), and to all later tiers through 60.3(c)(1), (d)(1), (e)(1)) [6]
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  (2) Review proposed development to assure that all necessary permits have been received from those governmental agencies from which approval is required by Federal or State law, including section 404 of the Federal Water Pollution Control Act Amendments of 1972, 33 U.S.C. 1334;

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• FEMA's study guide for local officials says a permit is required for all development in the SFHA shown on the FIRM, and lists excavation, filling, land clearing and grading among the activities that count as development. Communities have some discretion to exempt obviously insignificant activities, such as planting a garden, farming, putting up a mailbox or erecting a flagpole; the key is whether the project will present a new obstruction to flood flows, alter drainage or have the potential to be a substantial improvement. FEMA suggests any dollar-value exemption for small projects cover projects "other than filling, grading or excavating."

  Applies when: Pond excavation, embankment, fill or grading on land inside a mapped Special Flood Hazard Area in a community that participates in the NFIP FEMA, Floodplain Management Requirements study guide, Unit 5, pp. 5-17 to 5-19 [14]
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  Basic rule #2: A permit is required for all development in the SFHA shown on your FIRM....♦ Excavation ♦ Filling...♦ Land clearing ♦ Grading...You have some discretion to exempt obviously insignificant activities from the permit requirement, such as planting a garden, farming, putting up a mailbox or erecting a flagpole....The key is whether the project will present a new obstruction to flood flows, alter drainage or have the potential to be a substantial improvement....You may be able to exempt projects (other than filling, grading or excavating) valued at less than, say, $500.

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• FEMA's study guide advises that, under 44 CFR 60.3(a)(2), communities should not issue the local floodplain permit until they are certain that the other Federal and State agencies' permit requirements are met. It notes that some communities allow their permit officials to issue the local permit on the condition that other required permits are obtained, but says this is not as effective as holding the local permit until the applicant can show that the other agencies have issued or will issue their permits.

  Applies when: Pond excavation, embankment, fill or grading on land inside a mapped Special Flood Hazard Area in a community that participates in the NFIP FEMA, Floodplain Management Requirements study guide, Unit 5, p. 5-19 [14]
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  44 CFR 60.3(a)(2) requires all NFIP communities to ensure that other federal and state permits have been obtained. You should not issue your local permit until you are certain that the other agencies' requirements are met....Some communities allow their permit officials to issue the local permit on the condition that other required permits are obtained. However, this is not as effective as holding the local permit until the applicant can show that the other agencies have issued or will issue their permits.

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• RequirementIn riverine situations, before any alteration or relocation of a watercourse the community must notify adjacent communities and the State Coordinating Office and send copies of the notices to FEMA. It must also ensure that the flood carrying capacity within the altered or relocated portion of the watercourse is maintained.

  Applies when: A pond or embankment project that alters or relocates a watercourse in an NFIP community 44 CFR 60.3(b)(6)-(7) [6]
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  (6) Notify, in riverine situations, adjacent communities and the State Coordinating Office prior to any alteration or relocation of a watercourse, and submit copies of such notifications to the Federal Insurance Administrator; (7) Assure that the flood carrying capacity within the altered or relocated portion of any watercourse is maintained;

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• DefinitionA "violation" is the failure of a structure or other development to be fully compliant with the community's flood plain management regulations. A structure or other development that lacks the elevation certificate, other certifications, or other evidence of compliance required by 44 CFR 60.3(b)(5), (c)(4), (c)(10), (d)(3), (e)(2), (e)(4) or (e)(5) is presumed to be in violation until that documentation is provided. This list includes the encroachment analyses required for fill and other development under 60.3(c)(10) and in floodways under 60.3(d)(3).

  44 CFR 59.1 ("Violation") [1]
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  Violation means the failure of a structure or other development to be fully compliant with the community's flood plain management regulations. A structure or other development without the elevation certificate, other certifications, or other evidence of compliance required in § 60.3(b)(5), (c)(4), (c)(10), (d)(3), (e)(2), (e)(4), or (e)(5) is presumed to be in violation until such time as that documentation is provided.

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The one-foot rule, the floodway no-rise rule and variances

The base flood is the flood having a one percent chance of being equalled or exceeded in any given year; the regulations cross-reference the "100-year flood" to it. The regulatory floodway is the channel of a river or other watercourse plus the adjacent land that must be reserved to discharge the base flood without cumulatively raising the water surface more than a designated height, and once FEMA provides base flood elevations and floodway data, the community must select and adopt a floodway designed to carry the base flood without increasing its water surface elevation more than one foot at any point. [1][6]

FEMA's study guide for local officials (guidance, not regulation) says every project in the regulatory floodway must undergo an encroachment review and that the floodway standard in 44 CFR 60.3(d)(3) means zero increase, not a foot or a tenth of a foot. A community may require the applicant's engineer to certify that there will be no rise, often called a "no-rise" certification, or may make the determination itself for minor projects; the certification must be supported by technical data, which should be based on the same computer model used to develop the floodway shown on the community's map. [14]

The same guide notes that some States map floodways allowing flood heights to increase by less than one foot, and in those States the encroachment certification must be based on the more restrictive State standard. It also says a dam would have a major impact on flood heights, and that when a project will change the flood level, the maps must be changed to reflect the new hazard. [14]

Communities grant or deny variances after examining the applicant's hardship. Variances are generally limited to lots smaller than one-half acre, though deviations may occur and the technical justification required increases as lot size increases beyond one-half acre; no variance may be issued within a designated regulatory floodway if any increase in flood levels during the base flood discharge would result. A variance also requires a showing of good and sufficient cause, a determination that denying it would cause exceptional hardship to the applicant, and a finding that it will not result in increased flood heights, additional threats to public safety, extraordinary public expense, nuisances, fraud on or victimization of the public, or conflict with existing local laws or ordinances, and it must be the minimum necessary. [6]

As of the eCFR version history retrieved Sept. 28, 2026, the latest amendment date listed for 44 CFR Part 60 is Jan. 3, 2017, which is also the earliest date that record shows. The most recent entry for § 60.3 (issued Sept. 19, 2024) is marked non-substantive, so no substantive amendment to these criteria appears in that record. [15]

• DefinitionThe "base flood" is the flood having a one percent chance of being equalled or exceeded in any given year; the regulations cross-reference the "100-year flood" to this definition.

  44 CFR 59.1 ("Base flood"; "100-year flood") [1]
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  Base flood means the flood having a one percent chance of being equalled or exceeded in any given year....100-year flood see base flood.

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• DefinitionThe "regulatory floodway" (the regulations cross-reference "floodway" to it) is the channel of a river or other watercourse plus 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. Floodway encroachment lines are the lines marking the limits of floodways on Federal, State and local flood plain maps.

  44 CFR 59.1 ("Floodway"; "Floodway encroachment lines"; "Regulatory floodway") [1]
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  Floodway —see regulatory floodway....Floodway encroachment lines mean the lines marking the limits of floodways on Federal, State and local flood plain maps....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.

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• RequirementOnce FEMA has provided base flood elevations for Zones A1-30/AE and data for a floodway, the community must meet all the 60.3(c) requirements. It must also select and adopt a regulatory floodway designed to carry the base flood without increasing the water surface elevation of that flood more than one foot at any point.

  44 CFR 60.3(d)(1)-(2) [6]
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  (1) Meet the requirements of paragraphs (c) (1) through (14) of this section; (2) Select and adopt a regulatory floodway based on the principle that the area chosen for the regulatory floodway must be designed to carry the waters of the base flood, without increasing the water surface elevation of that flood more than one foot at any point;

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• FEMA guidance on floodway encroachments: every project in the regulatory floodway must undergo an encroachment review, and the 60.3(d)(3) standard means zero increase, not a foot or a tenth of a foot. A community may require the applicant's engineer to certify that there will be no rise in flood heights, or may make the determination itself for minor projects. The engineer's certification is often called a "no-rise" certification; it must be supported by technical data, which should be based on the same computer model used to develop the floodway shown on the community's map.

  Applies when: Pond embankments, spoil or fill inside a regulatory floodway FEMA, Floodplain Management Requirements study guide, Unit 5, pp. 5-21 to 5-23 [14]
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  All projects in the regulatory floodway must undergo an encroachment review...This doesn't mean you can allow a foot or a tenth of a foot – it means zero increase....For every project you could require the applicant's engineer to certify that there will be no rise in flood heights or you can make the determination for minor projects....This is often called a "no-rise" certification...The certification must be supported by technical data, which should be based on the same computer model used to develop the floodway shown on the commu nity's map.

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• FEMA notes that some States map floodways allowing flood heights to increase by less than one foot, and in those States the encroachment certification must be based on the more restrictive State standard, not the one-foot FEMA standard. FEMA also notes that a dam would have a major impact on flood heights, so a project that will change the flood level must be reflected in revised maps.

  Applies when: Embankment dams or fill affecting a mapped floodplain FEMA, Floodplain Management Requirements study guide, Unit 5, p. 5-25 [14]
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  In some states, floodways are mapped based on allowing flood heights to increase by less than one foot. In those states, the encroachment certification must be based on that more restrictive state standard, not the FEMA standard that allows a one-foot rise....Because a dam would have a major impact on flood heights, there needs to be a way to permit such projects, especially those that are intended to reduce flooding....However, when the project will change the flood level, maps must be changed to reflect the new hazard.

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• ExemptionCommunities grant or deny variances from the floodplain criteria after examining the applicant's hardship. Variances generally are limited to lots smaller than one-half acre; deviations from that limit may occur, but the technical justification required increases as lot size increases beyond one-half acre. A variance may not be issued within a designated regulatory floodway if any increase in flood levels during the base flood discharge would result.

  44 CFR 60.6(a), (a)(1) [6]
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  The community, after examining the applicant's hardships, shall approve or disapprove a request. While the granting of variances generally is limited to a lot size less than one-half acre...deviations from that limitation may occur. However, as the lot size increases beyond one-half acre, the technical justification required for issuing a variance increases....(1) Variances shall not be issued by a community within any designated regulatory floodway if any increase in flood levels during the base flood discharge would result;

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• RequirementA community may issue a floodplain variance only on a showing of good and sufficient cause, a determination that denial would cause exceptional hardship to the applicant, and a determination that the variance will not result in increased flood heights, additional threats to public safety, extraordinary public expense, nuisances, fraud on or victimization of the public, or conflict with existing local laws or ordinances. The variance must also be the minimum necessary.

  44 CFR 60.6(a)(3)-(4) [6]
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  (3) Variances shall only be issued by a community upon (i) a showing of good and sufficient cause, (ii) a determination that failure to grant the variance would result in exceptional hardship to the applicant, and (iii) a determination that the granting of a variance will not result in increased flood heights, additional threats to public safety, extraordinary public expense, create nuisances, cause fraud on or victimization of the public, or conflict with existing local laws or ordinances; (4) Variances shall only be issued upon a determination that the variance is the minimum necessary

  Open eCFR (Office of the Federal Register / GPO) (opens in a new tab)

• StatusStatus: according to the eCFR version history retrieved 2026-09-28, the latest amendment date for 44 CFR Part 60 (which contains the 60.3 permit, encroachment and no-rise criteria) is 2017-01-03, the earliest date shown in that record. The most recent 60.3 entry (issue date 2024-09-19) keeps the 2017-01-03 amendment date and is marked non-substantive, so no substantive amendment to these criteria appears in that record.

  eCFR version history, 44 CFR Part 60 [15]
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  {"date":"2017-01-03","amendment_date":"2017-01-03","issue_date":"2024-09-19","identifier":"60.3","name":"§ 60.3 Flood plain management criteria for flood-prone areas.","part":"60","substantive":false...."meta":{"title":"44","part":"60","result_count":"24","latest_amendment_date":"2017-01-03"

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Changing the flood map: CLOMR, LOMR and 44 CFR 65.12

A CLOMR is FEMA's comment on a proposed project that would, once built, affect the hydrologic or hydraulic characteristics of a flooding source and so modify the existing regulatory floodway, the effective base flood elevations or the SFHA; a CLOMR-F is FEMA's comment on a proposed project that would modify the SFHA by placing fill outside the existing floodway. A LOMR is FEMA's modification of an effective FIRM or Flood Boundary and Floodway Map, generally based on physical measures that affect the hydrologic or hydraulic characteristics of a flooding source, and officially revises the map; a LOMR-F modifies the SFHA based on fill placed outside the existing floodway. [10]

When a community proposes to permit encroachments that would raise base flood elevations beyond what the one-foot or floodway no-rise rules allow, it must apply to FEMA for conditional approval before permitting them. The application must include a request for conditional approval of the map change with the appropriate initial fee, and an evaluation of alternatives that would not exceed the allowed increase, showing why those alternatives are not feasible. It must also include documentation of individual legal notice to all impacted property owners inside and outside the community, the concurrence of the chief executive officer of any other impacted community, certification that no structures are located in areas the increased base flood elevation would affect, and requests for base flood elevation revision (under 44 CFR 65.6) and floodway revision (under 44 CFR 65.7). [9]

After conditional approval and before approving the encroachment, the community must show FEMA that it has adopted floodplain ordinances incorporating the increased base flood elevations and/or revised floodway for the post-project condition; when the encroachment is complete, the community must submit as-built certifications, and FEMA then starts a final map revision. [9]

A revision based on physical changes affecting hydrology (FEMA's examples include a dam, a diversion channel or a detention basin) must include a general description of the changes, as-built construction plans if applicable, a new hydrologic analysis, a new hydraulic analysis and profiles using the new flood discharges, and revised floodplain and floodway boundaries. A revision based on topographic changes (FEMA's examples are grading or filling) must include a general description of the changes, new topographic information and revised floodplain boundaries (and floodway, if necessary) and must show the changes have not resulted in a floodway encroachment. A CLOMR request needs the same data as a final revision except as-built certification. [9]

Analyses and data for a base flood elevation revision must be certified by a registered professional engineer or licensed land surveyor, as appropriate; for a floodway revision, all analyses must be certified by a registered professional engineer and topographic data by a registered professional engineer or licensed land surveyor. The community must also give FEMA written assurance that it has complied with the minimum 60.3 floodplain management requirements, including that it has issued permits for all existing and proposed construction or other development and that all permits required by Federal, State or local law have been received; if it cannot, the request is deferred until the community remedies all violations to the maximum extent possible through coordination with FEMA. [9]

When a LOMR-F (removing an area raised by earthen fill from the SFHA) involves structures, the community must also determine that the land and any existing or proposed structures to be removed are "reasonably safe from flooding." The requester must supply elevation information certified by a licensed land surveyor or registered professional engineer, and FEMA normally issues its determination within 60 days of a complete application. [16]

• DefinitionConditional (pre-construction) map products: a CLOMR is FEMA's comment on a proposed project that would, once built, affect the hydrologic or hydraulic characteristics of a flooding source and so modify the existing regulatory floodway, the effective base flood elevations, or the SFHA. A CLOMR-F is FEMA's comment on a proposed project that would, once built, modify the SFHA by placing fill outside the existing regulatory floodway.

  44 CFR 72.2 ("CLOMR"; "CLOMR-F") [10]
  Show the source text

  CLOMR. A CLOMR is FEMA's comment on a proposed project that would, upon construction, affect the hydrologic or hydraulic characteristics of a flooding source and thus result in the modification of the existing regulatory floodway, the effective base flood elevations, or the Special Flood Hazard Area (SFHA). CLOMR-F. A CLOMR-F is FEMA's comment on a proposed project that would, upon construction, result in a modification of the SFHA through the placement of fill outside the existing regulatory floodway.

  Open eCFR (Office of the Federal Register / GPO) (opens in a new tab)

• DefinitionFinal map products: a LOMR is FEMA's modification of an effective FIRM, Flood Boundary and Floodway Map, or both, generally based on physical measures that affect the hydrologic or hydraulic characteristics of a flooding source and so modify the regulatory floodway, the effective base flood elevations, or the SFHA; it officially revises the map. A LOMR-F is FEMA's modification of the SFHA on the FIRM based on fill placed outside the existing regulatory floodway.

  44 CFR 72.2 ("LOMR"; "LOMR-F") [10]
  Show the source text

  LOMR. A LOMR is FEMA's modification to an effective Flood Insurance Rate Map (FIRM), or Flood Boundary and Floodway Map (FBFM), or both. LOMRs are generally based on the implementation of physical measures that affect the hydrologic or hydraulic characteristics of a flooding source and thus result in the modification of the existing regulatory floodway, the effective base flood elevations, or the SFHA. The LOMR officially revises the FIRM or FBFM...LOMR-F. A LOMR-F is FEMA's modification of the SFHA shown on the FIRM based on the placement of fill outside the existing regulatory floodway.

  Open eCFR (Office of the Federal Register / GPO) (opens in a new tab)

• ProcessWhen a community proposes to allow floodplain encroachments (where no floodway is adopted) or floodway encroachments that would raise base flood elevations beyond what 60.3(c)(10) or (d)(3) allow, it must apply to FEMA for conditional approval before permitting them. The application must include a request for conditional approval with the appropriate initial fee, and an evaluation of alternatives that would not exceed the allowed increase, demonstrating why those alternatives are not feasible.

  Applies when: A dam or fill that would raise base flood elevations above the 60.3(c)(10) one-foot or 60.3(d)(3) zero-rise limits 44 CFR 65.12(a)(1)-(2) [9]
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  When a community proposes to permit encroachments upon the flood plain when a regulatory floodway has not been adopted or...upon an adopted regulatory floodway which will cause base flood elevation increases in excess of those permitted under paragraphs (c)(10) or (d)(3) of § 60.3...the community shall apply to the Federal Insurance Administrator for conditional approval...prior to permitting the encroachments...(1) A request for conditional approval of map change and the appropriate initial fee...(2) An evaluation of alternatives...demonstrating why these alternatives are not feasible;

  Open eCFR (Office of the Federal Register / GPO) (opens in a new tab)

• RequirementA 65.12 conditional-approval application must also include: documentation of individual legal notice to all impacted property owners inside and outside the community; concurrence of the chief executive officer of any other impacted community; certification that no structures are located in areas that would be affected by the increased base flood elevation; a request for revision of the base flood elevation determination under 65.6; and a request for floodway revision under 65.7.

  Applies when: A dam or fill that would raise base flood elevations above the 60.3(c)(10) one-foot or 60.3(d)(3) zero-rise limits 44 CFR 65.12(a)(3)-(7) [9]
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  (3) Documentation of individual legal notice to all impacted property owners within and outside of the community...(4) Concurrence of the Chief Executive Officer of any other communities impacted by the proposed actions; (5) Certification that no structures are located in areas which would be impacted by the increased base flood elevation; (6) A request for revision of base flood elevation determination according to the provisions of § 65.6 of this part; (7) A request for floodway revision in accordance with the provisions of § 65.7 of this part;

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• ProcessAfter FEMA grants conditional approval and before approving the encroachment, the community must show FEMA that it has adopted floodplain ordinances incorporating the increased base flood elevations and/or revised floodway for the post-project condition. When the encroachment is complete, the community must submit as-built certifications, and FEMA then starts a final map revision.

  Applies when: Projects that went through 65.12 conditional approval 44 CFR 65.12(b)-(c) [9]
  Show the source text

  (b) Upon receipt of the Federal Insurance Administrator's conditional approval of map change and prior to approving the proposed encroachments, a community shall provide evidence...of the adoption of flood plain management ordinances incorporating the increased base flood elevations and/or revised floodway reflecting the post-project condition. (c) Upon completion of the proposed encroachments, a community shall provide as-built certifications...The Federal Insurance Administrator will initiate a final map revision upon receipt of such certifications

  Open eCFR (Office of the Federal Register / GPO) (opens in a new tab)

• RequirementA map revision based on physical changes that affect hydrologic conditions (FEMA's examples include a dam, a diversion channel or a detention basin) must include: a general description of the changes; as-built construction plans, if applicable; a new hydrologic analysis accounting for the changes; a new hydraulic analysis and profiles using the new flood discharges; and revised floodplain and floodway boundaries.

  Applies when: Seeking a LOMR (or, with the same data minus as-built certification, a CLOMR) for a pond dam in a mapped floodplain 44 CFR 65.6(c)(1) [9]
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  (1) Changes affecting hydrologic conditions. The following data must be submitted: (i) General description of the changes (e.g., dam, diversion channel, or detention basin). (ii) Construction plans for as-built conditions, if applicable. (iii) New hydrologic analysis accounting for the effects of the changes. (iv) New hydraulic analysis and profiles using the new flood discharge values resulting from the hydrologic analysis. (v) Revised delineations of the flood plain boundaries and floodway.

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• RequirementAll analyses and data submitted for a base flood elevation revision must be certified by a registered professional engineer or licensed land surveyor, as appropriate. For floodway revisions, all analyses must be certified by a registered professional engineer, and topographic data by a registered professional engineer or licensed land surveyor. Base flood elevation revision requests go to the FEMA Regional Office serving the community or to FEMA Headquarters, with the appropriate payment (44 CFR Part 72).

  44 CFR 65.6(f)-(g); 65.7(d) [9]
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  All analysis and data submitted by the requester shall be certified by a registered professional engineer or licensed land surveyor, as appropriate...All requests shall be submitted to the FEMA Regional Office servicing the community's geographic area or to the FEMA Headquarters Office in Washington, DC, and shall be accompanied by the appropriate payment...All analyses submitted shall be certified by a registered professional engineer. All topographic data shall be certified by a registered professional engineer or licensed land surveyor.

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• ProcessFor a LOMR-F (removing an area raised by earthen fill from the SFHA) involving structures, the participating community must also determine that the land and any existing or proposed structures to be removed are "reasonably safe from flooding." The requester must supply elevation information certified by a Licensed Land Surveyor or Registered Professional Engineer. FEMA normally issues its determination within 60 days of a complete application. ESA compliance is required independently, and the community must ensure permits were obtained under 44 CFR 60.3(a)(2).

  Applies when: Spoil or fill placed in the SFHA (outside the floodway) that the owner wants removed from the flood zone FEMA, "Letter of Map Amendment & Letter of Map Revision-Based on Fill Process" [16]
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  The participating community must also determine that the land and any existing or proposed structures to be removed from the SFHA are "reasonably safe from flooding."...including elevation information certified by a Licensed Land Surveyor or Registered Professional Engineer....FEMA will normally complete its review and issue its determination in 60 days....Endangered Species Act compliance is required independently of FEMA's process. The community needs to ensure that permits are obtained per requirement under Section 60.3(a)(2) of FEMA's regulations.

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Fees, review times, filing and Endangered Species Act documentation

FEMA must receive the initial or flat fee before it begins any review, and the fee is non-refundable once review begins. The entity that applies to FEMA through the local community pays for the review, and the community incurs no financial obligation when another party sends the application. [10]

FEMA's fee page (last updated Jan. 19, 2023) publishes a fee schedule effective for requests postmarked on or after Feb. 20, 2015. With each fee shown here as online filing / paper filing, a CLOMR based on new hydrology, a bridge, culvert or channel, or a combination costs $6,500 / $6,750, and one based on a levee, berm or other structural measures $7,000 / $7,250 plus $60 an hour; a LOMR based on a bridge, culvert, channel, hydrology or a combination, or on as-built information following a CLOMR, costs $8,000 / $8,250, and one based on a levee, berm or other structural measures $9,000 / $9,250 plus $60 an hour. Single-lot or single-structure CLOMR-F and LOMR-F requests cost $325 to $600 depending on type and filing method, multiple-lot or multiple-structure CLOMR-F and LOMR-F requests $800 / $900, and a single-lot or single-structure LOMA is free. [17]

Fees are waived for, among other things, requests based on mapping or study analysis errors, natural changes within SFHAs, Letters of Map Amendment, and federally sponsored flood-control projects that are 50 percent or more federally funded; the separate exemption for information meant to improve a map or study does not cover improvements that partly or wholly incorporate man-made modifications within the SFHA. Under the Homeowner Flood Insurance Affordability Act of 2014, no fee is charged for a map change based on a project whose primary purpose is habitat restoration and that is funded in whole or in part with Federal or State funds, including dam removal, culvert redesign or installation, and fish passage. [10][17]

For CLOMR, LOMR and physical map revision requests, FEMA must notify the requester and community within 60 days whether the submittal is adequate and must respond within 90 days of receiving adequate information and the fee; for CLOMA, CLOMR-F, LOMA and LOMR-F requests the periods are 30 and 60 days. Under 44 CFR 65.9, within 90 days of receiving a revision request with all necessary information, FEMA must notify the community's chief executive officer of one or more listed outcomes, including approval by LOMR, a finding that another 90 days is needed to evaluate the data, or a request for more data; if the required payment has not been submitted, no review is conducted and no determination is issued until it is received. [9][10]

FEMA's LOMR/CLOMR page (last updated Mar. 25, 2026) says requests use FEMA's MT-2 forms and may be filed online through the Online Letter of Map Change (LOMC) tool, which FEMA recommends and which carries a lower fee, or by mail to the LOMC Clearinghouse. Under Cooperating Technical Partner agreements some States and local agencies review LOMRs and CLOMRs and have their own mail-in addresses. [12]

FEMA requires Endangered Species Act compliance documentation for CLOMR and CLOMR-F requests (FEMA page last updated July 2, 2025). For a non-federal project the requester determines whether there is any potential for "take" of a listed species, and that determination does not need to come from, or be concurred in by, the U.S. Fish and Wildlife Service or National Marine Fisheries Service; where take may occur, the requester can consider contacting those agencies to discuss project revisions that eliminate the take or, if that is not possible, submit an incidental take permit covering the project. Where federal construction, funding or permitting is involved in a project seeking a CLOMR or CLOMR-F, the applicant may use that agency's ESA Section 7 consultation to document ESA compliance to FEMA, and for LOMRs covering floodplain work already done, private individuals and local and State jurisdictions must comply with the ESA independently of FEMA's process. [18]

• FeeFEMA must receive the initial or flat user fee before it begins any review, and the fee is non-refundable once review begins. The entity that applies to FEMA through the local community is responsible for the cost of the review, and the local community incurs no financial obligation when another party sends the application.

  44 CFR 72.4(b), (e) [10]
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  (b) FEMA must receive initial or flat user fees before it will begin any review. The fee is non-refundable once FEMA begins its review....(e) The entity that applies to FEMA through the local community for review is responsible for the cost of the review. The local community incurs no financial obligation under the reimbursement procedures of this part when another party sends the application to FEMA.

  Open eCFR (Office of the Federal Register / GPO) (opens in a new tab)

• FeeFEMA's current published fee schedule (effective for requests postmarked on or after February 20, 2015), paper form fee / Online LOMC fee: CLOMR based on new hydrology, bridge, culvert, channel or combination: $6,750 / $6,500. CLOMR based on levee, berm or other structural measures: $7,250 / $7,000, plus $60/hr. LOMR based on bridge, culvert, channel, hydrology or combination: $8,250 / $8,000. LOMR based on levee, berm or other structural measures: $9,250 / $9,000, plus $60/hr. LOMR based on as-built information following a CLOMR: $8,250 / $8,000.

  Applies when: Requesting a CLOMR or LOMR for a pond dam, embankment or channel change FEMA, "Flood Map-Related Fees" (fee schedule per 44 CFR 72.3; Federal Register notice of Jan. 21, 2015) [17]
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  This fee schedule is effective for all requests post marked on or after February 20, 2015....CLOMR Based on New Hydrology, Bridge, Culvert, Channel or Combination Thereof $6,750 $6,500 CLOMR Based on Levee, Berm or Other Structural Measures $7,250 (plus $60/hr) $7,000 (plus $60/hr) LOMR Based on Bridge, Culvert, Channel, Hydrology, or Combination Thereof $8,250 $8,000 LOMR Based on Levee, Berm or Other Structural Measures $9,250 (plus $60/hr) $9,000 (plus $60/hr) LOMR Based on As-Built Information Submitted as a Follow-up to a CLOMR $8,250 $8,000

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• FeeFill-based map changes under the same fee schedule (paper / online): single-lot or single-structure LOMA: free. Single-lot/single-structure CLOMA and CLOMR-F: $600 / $500. Single-lot/single-structure LOMR-F: $525 / $425. Single-lot/single-structure LOMR-F based on as-built information after a CLOMR-F: $425 / $325. Multiple-lot/multiple-structure CLOMR-F and LOMR-F: $900 / $800.

  Applies when: Removing land raised with fill (for example, pond spoil) from the SFHA outside the floodway FEMA, "Flood Map-Related Fees" (fee schedule per 44 CFR 72.3) [17]
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  Single-Lot or Single-Structure LOMA Free Free Single-Lot/Single-Structure CLOMA and CLOMR-F $600 $500 Single-Lot/Single-Structure LOMR-F $525 $425 Single-Lot/Single-Structure LOMR-F Based on As-Built Information (CLOMR-F previously issued by FEMA) $425 $325...Multiple-Lot/Multiple-Structure CLOMR-F and LOMR-F $900 $800

  Open FEMA (opens in a new tab)

• TimelineRegulatory review timelines: for CLOMA, CLOMR-F, LOMA and LOMR-F requests, FEMA notifies the requester and community within 30 days whether the submittal is adequate and issues a determination within 60 days of receiving adequate information and the fee. For CLOMR, LOMR and physical map revision requests, FEMA notifies within 60 days about adequacy and responds within 90 days of receiving adequate information and the fee.

  44 CFR 72.4(g)-(h) [10]
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  (g) For CLOMA, CLOMR-F, LOMA, and LOMR-F requests, FEMA shall: (1) Notify the requester and community within 30 days as to the adequacy of the submittal, and (2) Provide to the requester and the community, within 60 days of receipt of adequate information and fee, a determination letter...(h) For CLOMR, LOMR, and PMR requests, FEMA shall: (1) Notify the requester and community within 60 days as to the adequacy of the submittal; and (2) Provide to the requester and the community, within 90 days of receipt of adequate information and fee, a CLOMR, a LOMR, other written comment

  Open eCFR (Office of the Federal Register / GPO) (opens in a new tab)

• ProcessLOMR and CLOMR requests use FEMA's MT-2 forms and can be filed online through the Online Letter of Map Change (LOMC) tool, which FEMA recommends and which carries a lower fee, or by mail to the LOMC Clearinghouse, 3601 Eisenhower Avenue, Suite 500, Alexandria, VA 22304-6426. Under Cooperating Technical Partner agreements, some States and local agencies review LOMRs and CLOMRs and have their own mail-in addresses. FEMA's page names Alabama, Colorado, Illinois, Indiana, North Carolina and Texas.

  FEMA, "Letters of Map Revision and Conditional Letters of Map Revision" [12]
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  MT-2 Requests may be submitted via mail or online. Online submittals offer a reduced review and processing fee....FEMA recommends an applicant use the Online Letter of Map Change tool...Letter of Map Change Clearinghouse 3601 Eisenhower Avenue, Suite 500 Alexandria, VA 22304-6426 Exception: In Cooperating Technical Partner (CTP) agreements with FEMA, the following counties or states will review and process Letters of Map Revisions and Conditional Letters of Map Revisions: Alabama, Colorado, Illinois, Indiana, North Carolina and Texas.

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• RequirementFEMA requires Endangered Species Act compliance documentation for Conditional Letters of Map Revision (including CLOMR-F). All private development projects must comply with the ESA independently of FEMA's process. For a non-federal project, the requester is responsible for determining whether there is any potential for "take," and that determination does not need to come from, or be concurred in by, the U.S. Fish and Wildlife Service or National Marine Fisheries Service.

  Applies when: Non-federal pond dam or fill projects seeking a CLOMR or CLOMR-F FEMA, "Required Endangered Species Act Compliance Documentation for Conditional Letter of Map Revision Requests" [18]
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  Required Endangered Species Act Compliance Documentation for Conditional Letter of Map Revision Requests...All proposed private development projects are required to comply with the ESA independently....The requester will be responsible for the potential for take determination and the determination is not required to come from, or be concurred by, the U.S. Department of Interior's Fish and Wildlife Service (USFWS) and the U.S. Department of Commerce's National Marine Fisheries Service (NMFS)

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Federal dam-safety context: hazard potential and the National Inventory of Dams

Federal guidelines classify dams in three hazard potential levels (low, significant and high) according to the potential for loss of life, economic loss and environmental damage from a hypothetical dam failure; FEMA points to Section III of FEMA 333, Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams (2004), for more on the system. As used in the National Inventory of Dams, the class indicates the potential hazard to the downstream area from failure or mis-operation of the dam and does not speak to the dam's condition or its risk of failing, and FEMA notes that State and Federal classification systems vary. [13][19]

Under the Interagency Committee on Dam Safety definitions, as given in the USACE NID Data Dictionary (Aug. 2024), a high hazard potential dam is one whose failure or mis-operation will probably cause loss of human life. A significant hazard potential dam's failure or mis-operation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities or other impacts; these dams are often in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure. A low hazard potential dam's failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses, principally limited to the owner's property. [13]

The National Dam Safety Program Act defines a dam as an artificial barrier that can impound water, wastewater or any liquid-borne material for storage or control of water and that either is 25 feet or more in height (from the natural bed of the stream channel or watercourse at the downstream toe, or, if the barrier is not across a stream channel or watercourse, from the lowest elevation of its outside limit, to the maximum water storage elevation) or has an impounding capacity of 50 acre-feet or more at maximum storage elevation. Levees are excluded. So is any barrier 6 feet or less in height regardless of storage capacity, or with a storage capacity of 15 acre-feet or less at maximum water storage elevation regardless of height, unless FEMA determines that, because of its location or another physical characteristic, the barrier is likely to pose a significant threat to human life or property if it fails. [20]

FEMA's Federal Guidelines for Dam Safety (FEMA P-93, December 2023) define a "dam or project" as an artificial barrier (including appurtenant works) that impounds or diverts water, liquid-borne solids or industrial wastes and is 25 feet or more in height or has 50 acre-feet or more of impounding capacity at maximum water storage elevation. They do not apply to a barrier not more than 6 feet high regardless of storage capacity, or with a storage capacity of not over 15 acre-feet regardless of height, but say that lower-size limit should be waived for dams with a high or significant hazard potential classification; the capacity counted includes floodwater storage above the normal full storage elevation. The guidelines apply to federal practices for dams with a direct federal interest, may also be used by non-federal dam owners, regulators and operators, and are not intended to supplant State, tribal or local dam-safety responsibilities. [21][22]

The NID measures height three ways and uses the largest, "NID Height," as the dam's general height: dam height (lowest point of the crest to the lowest point of the original streambed), hydraulic height (maximum design water level to that streambed) and structural height (lowest point of the excavated foundation to the top of the dam). It lists a dam as State regulated only if the State has permitting, inspection and enforcement authority and the dam meets the State's jurisdictional-dam definition; those definitions differ, and the example the NID Data Dictionary (Aug. 2024) gives is New Mexico, where a dam exceeding 10 feet in height regardless of storage, or storing more than 10 acre-feet regardless of height, is jurisdictional. [13]

Congress authorized USACE to maintain the NID; about 75 percent of NID dams are regulated by State dam safety offices and almost 70 percent are privately owned, and FEMA's National Dam Safety Program provides grant assistance to State dam safety programs. FEMA's Dam Awareness fact sheet (May 2018) says responsibility for operating and maintaining a safe dam rests with the owner, the extent of an owner's liability varies from State to State, and owners can be fiscally and criminally liable for any failure of a dam and all resulting damages. [19][23][24]

• DefinitionHazard potential classification (as used in the NID): a category that indicates the potential hazard to the downstream area from failure or mis-operation of the dam, reflecting probable loss of human life and impacts on economic, environmental and lifeline interests. It does not speak to the condition of the dam or the risk of the dam failing. The classes are Low, Significant, High and Undetermined, and the definitions are those accepted by the Interagency Committee on Dam Safety.

  USACE, National Inventory of Dams Data Dictionary (Aug. 2024), "Hazard Potential Classification" [13]
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  Category to indicate the potential hazard to the downstream area resulting from failure or mis-operation of the dam or facilities. It reflects probable loss of human life and impacts on economic, environmental, and lifeline interests. The hazard potential does not speak to the condition of the dam or the risk of the dam failing. Low Significant High Undetermined Definitions, as accepted by the Interagency Committee on Dam Safety, are as follows:

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• DefinitionHigh hazard potential: dams where failure or mis-operation will probably cause loss of human life. In the NID's summary table, loss of human life is "Probable. One or more expected," and economic, environmental and lifeline losses are not necessary for this classification.

  USACE, NID Data Dictionary (Aug. 2024), "High Hazard Potential" (Interagency Committee on Dam Safety definition) [13]
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  High Hazard Potential Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life....High Probable. One or more expected...(but not necessary for this classification)

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• DefinitionSignificant hazard potential: dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or impact other concerns. These dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.

  USACE, NID Data Dictionary (Aug. 2024), "Significant Hazard Potential" (Interagency Committee on Dam Safety definition) [13]
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  Significant Hazard Potential Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.

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• DefinitionLow hazard potential: dams where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses, with losses principally limited to the owner's property.

  USACE, NID Data Dictionary (Aug. 2024), "Low Hazard Potential" (Interagency Committee on Dam Safety definition) [13]
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  Low Hazard Potential Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.

  Open U.S. Army Corps of Engineers (opens in a new tab)

• DefinitionUnder the National Dam Safety Program Act, a "dam" is any artificial barrier able to impound water, wastewater or any liquid-borne material for storage or control of water that either (i) is 25 feet or more in height, measured from the natural bed of the stream channel or watercourse at the downstream toe of the barrier (or, if the barrier is not across a stream channel or watercourse, from the lowest elevation of its outside limit) to the maximum water storage elevation, or (ii) has an impounding capacity of 50 acre-feet or more at maximum storage elevation.

  33 U.S.C. 467(3)(A) [20]
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  (A) means any artificial barrier that has the ability to impound water, wastewater, or any liquid-borne material, for the purpose of storage or control of water, that- (i) is 25 feet or more in height from- (I) the natural bed of the stream channel or watercourse measured at the downstream toe of the barrier; or (II) if the barrier is not across a stream channel or watercourse, from the lowest elevation of the outside limit of the barrier; to the maximum water storage elevation; or (ii) has an impounding capacity for maximum storage elevation of 50 acre-feet or more

  Open Office of the Law Revision Counsel, U.S. House of Representatives (opens in a new tab)

• ExemptionThe National Dam Safety Program Act definition of "dam" excludes levees. It also excludes any barrier 6 feet or less in height regardless of storage capacity, or with storage of 15 acre-feet or less at maximum water storage elevation regardless of height, unless FEMA determines that the barrier is likely to pose a significant threat to human life or property if it fails because of its location or another physical characteristic.

  33 U.S.C. 467(3)(B) [20]
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  (B) does not include- (i) a levee; or (ii) a barrier described in subparagraph (A) that- (I) is 6 feet or less in height regardless of storage capacity; or (II) has a storage capacity at the maximum water storage elevation that is 15 acre-feet or less regardless of height; unless the barrier, because of the location of the barrier or another physical characteristic of the barrier, is likely to pose a significant threat to human life or property if the barrier fails (as determined by the Administrator).

  Open Office of the Law Revision Counsel, U.S. House of Representatives (opens in a new tab)

• DefinitionFor the Federal Guidelines for Dam Safety, a "dam or project" is an artificial barrier (including appurtenant works) that impounds or diverts water, liquid-borne solids or industrial wastes and either (1) is twenty-five feet or more in height from the natural bed of the stream or watercourse at the downstream toe of the barrier to the maximum water storage elevation, or (2) has an impounding capacity of fifty acre-feet or more at maximum water storage elevation.

  FEMA P-93, Federal Guidelines for Dam Safety (Dec. 2023), Ch. 1, Sec. B (Definitions: "Dam or Project") [21]
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  Dam or Project: Any artificial barrier, including appurtenant works, that impounds or diverts water, liquid-borne solids, or industrial wastes, and (1) is twenty-five feet or more in height from the natural bed of the stream or watercourse measured at the downstream toe of the barrier...to the maximum water storage elevation or (2) has an impounding capacity at maximum water storage elevation of fifty acre-feet or more.

  Open FEMA / Interagency Committee on Dam Safety (opens in a new tab)

• ExemptionThe Federal Guidelines for Dam Safety do not apply to a barrier that is not more than six feet high, regardless of storage capacity, or that has a storage capacity at maximum water storage elevation of not over fifteen acre-feet, regardless of height. That lower size limitation should be waived for dams with a high or significant hazard potential classification. The impounding capacity counted includes storage of floodwaters above the normal full storage elevation.

  FEMA P-93, Federal Guidelines for Dam Safety (Dec. 2023), Ch. 1, Sec. B (Definitions: "Dam or Project") [21]
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  These guidelines do not apply to any barrier that is not more than six feet in height, regardless of storage capacity, or has a storage capacity at maximum water storage elevation not over fifteen acre-feet, irrespective of height. This lower-size limitation should be waived for dams or projects with a high or significant hazard potential classification....The impounding capacity at maximum storage elevation includes storage of floodwaters above the normal full storage elevation.

  Open FEMA / Interagency Committee on Dam Safety (opens in a new tab)

• DefinitionHow the NID measures height: "Dam Height" is the vertical distance between the lowest point on the crest of the dam and the lowest point in the original streambed. "Hydraulic Height" runs from the maximum design water level to the lowest point in the original streambed. "Structural Height" runs from the lowest point of the excavated foundation to the top of the dam. "NID Height" is the maximum of the three and is accepted as the general height of the dam.

  USACE, NID Data Dictionary (Aug. 2024), "Dam Height", "Hydraulic Height", "Structural Height", "NID Height" [13]
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  Dam Height Height of the dam...defined as the vertical distance between the lowest point on the crest of the dam and the lowest point in the original streambed. Hydraulic Height...defined as the vertical difference between the maximum design water level and the lowest point in the original streambed. Structural Height...defined as the vertical distance from the lowest point of the excavated foundation to the top of the dam....NID Height Calculated field: Maximum value of dam height, structural height, and hydraulic height. Accepted as the general height of the dam.

  Open U.S. Army Corps of Engineers (opens in a new tab)

• The NID treats a dam as "state regulated" only if the State regulatory organization has all four authorities for that dam: permitting, inspection, enforcement, and the dam meeting the State's definition of a jurisdictional dam. State jurisdictional definitions differ. The NID's example is New Mexico, where a jurisdictional dam is one that exceeds 10 feet in height regardless of storage, or stores more than 10 acre-feet regardless of height.

  USACE, NID Data Dictionary (Aug. 2024), "State Regulated Dam", "State Jurisdictional Dam" [13]
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  Calculated field: based on State Permitting Authority, State Inspection Authority, State Enforcement Authority, and State Jurisdictional Dam. If Yes to all four authority criteria, then the dam is considered state regulated and listed as Yes....State Jurisdictional Dam Listed as Yes if this dam meets the state regulatory organization's definition of a jurisdictional dam. For example, in New Mexico a jurisdictional dam is defined as a dam that exceeds 10 feet in height regardless of storage or a dam that stores more than 10 acre-feet regardless of height.

  Open U.S. Army Corps of Engineers (opens in a new tab)

• FEMA: responsibility for operating and maintaining a safe dam rests with the owner. Common law holds that storing water is a hazardous activity, the extent of an owner's liability varies from State to State depending on statutes and case law, and owners can be fiscally and criminally liable for any failure of a dam and all damages resulting from it.

  FEMA, "Dam Awareness" fact sheet (May 2018), "Responsibility and Liability for Dam Safety" [19]
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  The responsibility for operating and maintaining a safe dam rests with the owner. Common law holds that the storage of water is a hazardous activity. Maintaining a safe dam is a key element in preventing failure and limiting the liability that an owner could face. The extent of an owner's liability varies from state to state and depends on statutes and case law precedents....Owners can be fiscally and criminally liable for any failure of a dam and all damages resulting from its failure.

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