Town of Antrim, NH
Article XII - Floodplain Development District (FDD)
(Adopted March 13, 1990; Amended March 8,1994; Amended March 13, 2007)
XII - 1
(Adopted March 13, 1990, Amended March 8, 1994, Amended March 13, 2007)

A.       Purpose

The Floodplain Development District is intended to protect all lands designated as special flood hazard areas by the Federal Emergency Management Agency in its “Flood Insurance Study for the County of Hillsborough, NH” dated September 25, 2009, together with the associated Flood Insurance Rate Maps dated September 25, 2009, which are declared to be part of this ordinance.

B.      Definition of Terms

1.      “Area of Special Flood Hazard” is the land in the floodplain within the Town of Antrim subject to a one-percent or greater chance of flooding in any given year. The area is designated as Zone(s) A and AE on the Flood Insurance Rate Map (FIRM).

“Base Flood” means the flood level having a one-percent chance of being equaled or exceeded in any given year.

3.      “Basement” means any area of a building having its floor subgrade on all sides.

4.      “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, drilling operations, or storage of equipment or materials.

5.      “Flood” or “Flooding” means a general and temporary condition of partial or complete inundation of normally dry land areas from:

a.      The overflow of inland or tidal waters.
b.      The usual and rapid accumulation of runoff of surface waters from any source.

6.      “Flood Elevation Study” means an examination, evaluation, and determination of flood hazards and, if appropriate, corresponding water surface elevations, or an examination and determination of mudslide or flood-related erosion hazards.

7.      “Flood Insurance Rate Map” (FIRM) means an official map of a community on which FEMA has delineated both the special flood hazard areas and the risk premium zones applicable to the community.

8.      “Flood Insurance Study” - see “Flood Elevation Study”.

9.      “Floodplain” or “Flood-prone area” means any land area susceptible to being inundated by water from any source (see definition of “Flooding”).

10.     “Flood proofing” means any combination of structural and non-structural additions, changes, or adjustments to structures which reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, structures and their contents.

11.     “Floodway” - see “Regulatory Floodway”.

12.     “Functionally dependent use” means a use which cannot perform its intended purpose unless it is located or carried out in close proximity to water. The term includes only docking and port facilities that are necessary for the loading/unloading of cargo or passengers, and ship building/repair facilities but does not include long-term storage or related manufacturing facilities.

13.     “Highest Adjacent Grade” means the highest natural elevation of the ground surface prior to construction next to the proposed walls of a structure.

14.     “Historic Structure” means any structure that is:

a.      Listed individually in the National Register of Historic Places (a listing maintained by the Department of the Interior as meeting the requirements for individual listing on the National Register).

b.      Certified or preliminarily determined by the Secretary of the Interior as contributing to the historical significance of a registered historic district or a district preliminarily determined by the Secretary to qualify as a registered historic district.

c.      Individually listed on a state inventory of historic places in states with historic preservation programs which have been approved by the Secretary of the Interior.

d.      Individually listed on a local inventory of historic places in communities with historic preservation programs that have been certified either:

(1)     By an approved state program as determined by the Secretary of the Interior.

(2)     Directly by the Secretary of the Interior in states without approved programs.

15.     “Lowest Floor” means the lowest floor of the lowest enclosed area (including basement). An unfinished or flood-resistant enclosure, usable solely for parking of vehicles, building access or storage in an area other than a basement area is not considered a building’s lowest floor; provided, that such an enclosure is not built so as to render the structure in violation of the applicable non-elevation design requirements of this ordinance.

16.     “Manufactured Home” means a structure, transportable in one or more sections, which is built on a permanent chassis and is designed for use with or without a permanent foundation when connected to the required utilities. For floodplain management purposes the term “manufactured home” includes park trailers, travel trailers, and other similar vehicles placed on site for greater than 180 consecutive days.  This includes manufactured homes located in a manufactured home park or subdivision.

17.     “Manufactured Home Park or Subdivision” means a parcel (or contiguous parcels) of land divided into two or more manufactured home lots for rent or sale.

18.     “Mean Sea Level” means the National Geodetic Datum (NGVD) of 1929 or other datum, to which base flood elevations shown on a FIRM are referenced.

19.     “New Construction” means, for the purposes of determining insurance rates, structures for which the “start of construction” commenced on or after the effective date of an initial FIRM or after December 31, 1974, whichever is later, and includes any subsequent improvements to such structures.  For floodplain management purposes, new construction means structures for which the start of construction commenced on or after the effective date of a floodplain management regulation adopted by a community and includes any subsequent improvements to such structures.

20.     “100 - year Flood” - see “Base Flood”.

21.     “Regulatory Floodway” means the channel of a river or other watercourse and 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.

22.     “Recreational Vehicle” means a vehicle which is:

a.      built on a single chassis;

b.      400 square feet or less measured at the largest horizontal projection;

c.      designed to be self propelled or permanently towable by a light duty truck; and

d.      designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, camping, travel or seasonal use.

23.     “Special Flood Hazard Areas” - see “Area of Special Flood Hazard”.

24.     “Structure” means, for floodplain management purposes, a walled and roofed building, including a gas or liquid storage tank, that is principally above ground, as well as a manufactured home.

25.     “Start of Construction” includes substantial improvements, and means the date the building permit was issued, provided the actual start of construction, repair, reconstruction, placement, or other improvement was within 180 days of the permit date. The actual start means either the first placement of permanent construction of a structure on site, such as the pouring of slab or footings, the installation of piles, the construction of columns, or any work beyond the stage of excavation or the placement of a manufactured home on a foundation. Permanent construction does not include land preparation, such as clearing, grading and filling; nor does it include the installation of streets and/or walkways; nor does it include excavation for a basement, footings, piers or foundations or the erection of temporary forms; nor does it include the installation on the property of accessory buildings, such as garages or sheds not occupied as dwelling units or part of the main structure.

26.     “Substantial Damage” means damage of any origin sustained by a structure whereby the cost of restoring the structure to its before damaged condition would equal or exceed 50 percent of the market value of the structure before the damage occurred.

27.     “Substantial Improvement” means any combination of repairs, reconstruction, alteration, or improvements to a structure in which the cumulative cost equals or exceeds 50 percent of the market value of the structure. The market value of the structure should equal:

a.      The appraised value prior to the start of the initial repair or improvement.

b.      In the case of damage, the value of the structure prior to the damage occurring. For the purposes of this definition, “substantial improvement” is considered to occur when the first alteration of any wall, ceiling, floor, or other structural part of the building commences, whether or not that alteration affects the external dimensions of the structure. This term includes structures which have incurred substantial damage, regardless of actual repair work performed. The term does not, however, include any project for improvement of a structure required to comply with existing health, sanitary, or safety code specifications which are solely necessary to assure safe living conditions or any alteration of a “historic structure”, provided the alteration will not preclude the structure’s continued designation as a “historic structure”.
28.     “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 44CFR § 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.

29.     “Water Surface Elevation” means the height, in relation to the National Geodetic Vertical Datum (NGVD) of 1929, (or other datum, where specified) of floods of various magnitudes and frequencies in the floodplains.

C.      Permit

All proposed development in any special flood hazard areas shall require a permit. The Building Inspector or designated town agent shall review all building permit applications for new construction or substantial improvements to determine whether the proposed building site is in a floodprone area further, all new construction of substantial improvements shall:

1.      Be designed or modified and adequately anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.

2.      Be constructed with materials resistant to flood damage.

3.      Be constructed by methods and practices that minimize flood damage.

4.      Be constructed with electrical, heating, ventilation, plumbing and air conditioning equipment, and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding.

D.      Water and Sewer Systems

Where new or replacement water and sewer systems (including on-site systems) are proposed in floodprone areas the applicant shall provide the Building Inspector with assurance that these systems will be designed to minimize or eliminate infiltration of flood waters into the systems and discharges from the systems into flood waters, and on-site waste disposal systems will be located to avoid impairment to them or contamination from them during periods of flooding.

E.      Certification of Flood-Proofing

The Building Inspector shall maintain for public inspection, and furnish upon request, any certification of flood-proofing and the as-built elevation (in relation to mean sea level) of the lowest floor (including basement) of all new or substantially improved structures, and include whether or not such structures contain a basement. If the structure has been floodproofed, certification shall include the as-built elevation (in relation to mean sea level) to which the structure was floodproofed. This information must be furnished by the applicant.

F.      Permits from State and Federal Agencies

The Building Inspector shall review proposed developments 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. It shall be the responsibility of the applicant to certify these assurances to the Building Inspector.

G.      Alteration or Relocation of a Watercourse

1.      In riverine situations, prior to the alteration or relocation of a watercourse, the applicant for such authorization shall notify the Wetlands Board of the New Hampshire Environmental Services Department and submit copies of such notification to the Building Inspector. Further, the applicant shall be required to submit copies of said notification to adjacent communities as determined by the Building Inspector.

2.      The applicant shall submit to the Building Inspector certification provided by a registered professional engineer assuring that the flood carrying capacity of an altered or relocated watercourse can and will be maintained.

3.      Along watercourses with a designated Regulatory Floodway no encroachments, including fill, new construction, substantial improvements, and other development are allowed within the floodway unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practices that the proposed encroachment would not result in any increase in flood levels within the community during the base flood discharge.

4.      Along watercourses that have not had a Regulatory Floodway designated, no new construction, substantial improvements, or other development (including fill) shall be permitted within zone AE on the FIRM, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all 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.

5.      The Building Inspector shall obtain, review, and reasonably utilize any floodway data available from Federal, State, or other sources as criteria for requiring that all development located in Zone A meet the following floodway requirement:

"No encroachments, including fill, new construction, substantial improvements, and other development are allowed within the floodway that would result in any increase in flood levels within the community during the base flood discharge.”

H.      Construction in Flood Hazard Areas

1.      In special flood hazard areas, the Building Inspector shall determine the 100-year flood elevation in the following order of precedence according to the data available.

a.      In zone AE, refer to the elevation data provided in the community’s Flood Insurance Study and accompanying FIRM.

b.      In zone A, the Building Inspector shall obtain, review, and reasonably utilize any 100-year flood elevation data available from federal and state agencies, and development proposals submitted to the community (i.e. subdivisions, site plans or other sources).

2.      The Building Inspector’s 100-year flood elevation determination will be used as criteria for requiring in zones A and AE that:

a.      All new construction or substantial improvements of residential structures have the lowest floor (including basement) elevated to or above the 100-year flood elevation.

b.      All new construction or substantial improvement of non-residential structures have the lowest floor (including basement) elevated to or above the 100-year flood level; or together with attendant utility and sanitary facilities shall:

(1)     Be floodproofed so that below the 100 year flood elevation the structure is watertight with walls substantially impermeable to the passage of water.

(2)     Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy.

(3)     Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting the provisions of this section.

c.      Recreational vehicles placed on sites within zones A and AE shall either:

(1)     be on the site for fewer than one hundred eighty (180) consecutive days,

(2)     be fully licensed and ready for highway use,

(3)     meet all standards of Section 60.3 (b) (1) of the National Flood Insurance Program Regulations and the elevation and anchoring requirements for “manufactured homes” in paragraph (c) (6) of Section 60.3.

d.      All manufactured homes to be placed or substantially improved within special flood hazard areas shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is at or above the base flood level; and be securely anchored to resist flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.

e.      For all new construction and substantial improvements, fully enclosed areas below the lowest floor that are subject to flooding meet the following requirements.

(1)     The enclosed area is unfinished or flood resistant, or used solely for the parking of vehicles, building access or storage.

(2)     The area is not a basement.

(3)     Shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or must meet or exceed the following minimum criteria: A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided. The bottom of all openings shall be no higher than one foot above grade. Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.

Variances and Appeals

Any order, requirement, decision or determination of the building inspector made under this ordinance may be appealed to the Zoning Board of Adjustment as set forth in RSA 676:5.

If the applicant, upon appeal, requests a variance as authorized by RSA 674:33, I(b), the applicant shall have the burden of showing in addition to the usual variance standards under state law that:

The variance will not result in increased flood heights, additional threats to public safety, or extraordinary public expense.
If the requested variance is for activity within a designated regulatory floodway, no increase in flood levels during the base flood discharge will result.
The variance is the minimum necessary, considering the flood hazard, to afford relief.

The Zoning Board of Adjustment shall notify the applicant in writing that:

The issuance of a variance to construct below the base flood level will result in increased premium rates for flood insurance up to amounts as high as $25.00 for $100.00 of insurance coverage; and
Such construction below the base flood level increases risks to life and property.

Such notification shall be maintained with a record of all variance actions.

The community shall:

Maintain a record of all variance actions, including the justification for their issuance, and
Report such variances issued in its annual or biennial report submitted to FEMA’s Federal Insurance Administrator.

Updated 3/13/07