Derry City Zoning Code
ARTICLE VII
Floodplain Development District
§ 165-50 Applicability.
The following regulations in this section shall apply to all lands designated as special flood hazard areas by the Federal Emergency Management Agency (FEMA) in its Flood Insurance Study of the County of Rockingham, NH, dated May 17, 2005, or as amended, together with the associated Flood Insurance Rate Maps (FIRM), dated May 17, 2005, or as amended, which are declared to be a part of this chapter and are hereby incorporated by reference.
§ 165-51 Definitions.
[Amended 6-5-2007; 2-16-2012; 9-13-2023]
For purposes of this article, certain words or terms shall be interpreted as defined herein. Where the definition of a word or term contained in this section conflicts with a similar word or term as defined in Article II of this chapter, the definition contained in this section shall apply only to these floodplain development provisions.
The floodplain within the Town of Derry subject to a one-percent or greater possibility of flooding in any given year. The area designated on the FIRM as Zones A and AE.
The flood having a one percent possibility of being equaled or exceeded in any given year.
The elevation of surface water resulting from the “base flood.”
Any area of a building having its floor subgrade (below ground level) on all sides.
See "structure."
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, as defined by FEMA.
The Federal Emergency Management Agency.
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.
An official map incorporated with this chapter on which FEMA has delineated both the special flood hazard areas and the risk premium zones applicable to the Town of Derry.
An opening in a foundation or enclosure wall that allows automatic entry and exit of floodwaters. See FEMA “Technical Bulletin 1, Openings in Foundation Walls and Walls of Enclosures.”
A general and temporary condition of partial or complete inundation of normally dry land areas from:
Any land area susceptible to being inundated by water from any source. (See definition of "flooding.")
Any combination of structural and nonstructural additions, changes or adjustments to structures which reduce or eliminate flood damage to real estate or improved real property, water and sanitation facilities, structures and their contents.
See "regulatory floodway."
The highest natural elevation of the ground surface prior to construction next to the proposed walls of a structure.
Any structure that is:
Listed individually in the National Register of Historic Places (a listing maintained by the Department of Interior), or preliminarily determined by the Secretary of the Interior as meeting the requirements for individual listing on the National Register;
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;
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; or
Individually listed on a local inventory of historic places in communities with historic preservation programs that have been certified either:
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 enclosure is not built so as to render the structure in violation of the applicable nonelevation design requirements of this chapter.
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 a site for greater than 180 days. This includes manufactured homes listed in a manufactured home park or subdivision.
A parcel (or contiguous parcels) of land divided into two or more manufactured home lots for rent or sale.
The National Geodetic Vertical Datum (NGVD) of 1929, or other datum, to which base flood elevations shown on a community's Flood Insurance Rate Map are referenced.
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.
Defined as:
Built on a single chassis;
Four hundred square feet or less when measured at the largest horizontal projection;
Designed to be self-propelled or permanently towable by a light-duty truck; and
Designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, camping, travel or seasonal use.
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.
See "area of special flood hazard."
Includes substantial improvements, and means the date the building permit was issued, provided that 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 a site, such as the pouring of slab or footings, the installation of piles, the construction of columns, or any work beyond the state 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.
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.
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% of the market value of the structure before the damage occurred.
Any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds 50% of the market value of the structure before the “start of construction” of the improvement. This term includes structures which have incurred “substantial damage,” regardless of actual repair work performed. The term does not, however, include either:
Any project for improvement of a structure to correct existing violations of state or local health, sanitary or safety code specifications which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions; or
Any alteration of a “historic structure,” provided that the alteration will not preclude the structure’s continued designation as a “historic structure.”
The failure of a structure or other development to be fully compliant with the community's floodplain management regulations. A structure or other development without the elevation certificate, other certifications, or other evidence of compliance required under § 165-55, 165-58B(2) or 165-57C and D of this chapter is presumed to be in violation until such time as that documentation is provided.
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.
§ 165-52 Permit required.
All proposed development in any special flood hazard areas shall require a permit.
§ 165-53 New construction or substantial improvements.
The Building Inspector shall review all building permit applications for new construction or substantial improvements to determine whether proposed building sites will be reasonably safe from flooding. If a proposed building site is located in a special flood hazard area, all new construction and substantial improvements shall be:
A.
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;
B.
Constructed with materials resistant to flood damage;
C.
Constructed by methods and practices that minimize flood damage; and
D.
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.
§ 165-54 Water and sewer systems.
Where new and replacement water and sewer systems (including on-site systems) are proposed in a special flood hazard area, the applicant shall provide the Building Inspector with assurance that these systems will be designed to minimize or eliminate infiltration of floodwaters into the systems and discharges from the systems into floodwaters, and on-site waste disposal systems will be located to avoid impairment to them or contamination from them during periods of flooding.
§ 165-55 Certification.
[Amended 2-16-2012; 9-13-2023]
A.
For all new or substantially improved structures located in Zones A and AE, the applicant shall furnish the following information to the Building Inspector:
(1)
The as-built elevation (in relation to mean sea level) of the lowest floor (including basement) and include whether or not such structures contain a basement.
(2)
If the structure has been floodproofed, the as-built elevation (in relation to mean sea level) to which the structure was floodproofed.
(3)
Any certification of floodproofing.
B.
The Building Inspector shall maintain for public inspection and shall furnish such information upon request.
§ 165-56 Permits from federal or state agencies.
The Building Inspector shall not grant a building permit until the applicant certifies 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.
§ 165-57 Alteration or relocation of watercourse.
[Amended 2-16-2012; 9-13-2023]
A.
In riverine situations, prior to the alteration or relocation of a watercourse, the applicant for such authorization shall notify the Wetlands Bureau of the New Hampshire Department of Environmental Services and submit copies of such notification to the Building Inspector, in addition to the copies required by RSA 482-A:3. Further, the applicant shall be required to submit copies of said notification to those adjacent communities as determined by the Building Inspector, including notice of all scheduled hearings before the Wetlands Bureau.
B.
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.
C.
Along watercourses that have a designated regulatory floodway, no encroachments, including fill, new construction, substantial improvements, or other development, are allowed within the floodway that would result in any increase in flood levels within the community during the base flood discharge.
D.
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 by the applicant 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.
E.
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." |
§ 165-58 Determination of flood elevation.
[Amended 2-16-2012; 9-13-2023]
A.
In special flood hazard areas, the Building Inspector shall determine the base flood elevation in the following order of precedence according to the data available:
(1)
In Zone AE, refer to the elevation data provided in the community's Flood Insurance Study and accompanying FIRM.
(2)
In Zone A, the Building Inspector shall obtain, review and reasonably utilize any one-hundred-year flood elevation data available from federal, state, or other sources, including data submitted for development proposals submitted to the community, e.g., subdivisions, site approvals, etc. Where a base flood elevation is not available or not known for Zone A, the base flood elevation shall be determined to be at least two feet above the highest adjacent grade.
B.
The Building Inspector's base flood elevation determination will be used as criteria for requiring, in Zones A and AE, that:
(1)
All new construction and substantial improvements of residential structures have the lowest floor (including basement) elevated to or above the base flood elevation;
(2)
All new construction and substantial improvements of nonresidential structures have the lowest floor (including basement) elevated to or above the base flood level, or, together with attendant utility and sanitary facilities, shall:
(a)
Be floodproofed so that below the base flood elevation the structure is watertight, with walls substantially impermeable to the passage of water;
(b)
Have structural components capable of resisting hydrostatic and hydrodynamic loads and the effects of buoyancy; and
(c)
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.
(3)
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.
(4)
Recreation vehicles placed on sites within Zones A and AE shall either:
(a)
Be on the site for fewer than 180 consecutive days;
(b)
Be fully registered, on wheels or jacking system, attached to the site only by quick disconnect type of utilities and security devices, and have no permanently attached additions;
(c)
Meet all standards of this article and the elevation and anchoring requirements for manufactured homes in this article.
(5)
For all new construction and substantial improvements, fully enclosed areas below the lowest floor that are subject to flooding are permitted, provided that the enclosed areas meet the following requirements:
(a)
The enclosed area is unfinished or flood-resistant, usable solely for parking of vehicles, building access, or storage;
(b)
The area is not a basement; and
(c)
The area shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwater. 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:
[1]
A minimum of two flood 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.
[2]
The bottom of all openings shall be no higher than one foot above grade.
[3]
Openings may be equipped with screens, louvers, or other coverings or devices, provided that they permit the automatic entry and exit of floodwater.
§ 165-59 Variances and appeals.
[Amended 2-16-2012; 9-13-2023]
A.
Any order, requirement, decision or determination of the Building Inspector made under these floodplain development regulations may be appealed to the Zoning Board of Adjustment as set forth in RSA 676:5.
B.
If the applicant, upon appeal, requests a variance as authorized by RSA 674:33, I, in determining whether or not any variance will be contrary to the spirit of these regulations, the Board of Adjustment shall consider the following:
(1)
That the variance will not result in increased flood heights, additional threats to public safety, or extraordinary public expense;
(2)
That, if the requested variance is for activity within a designated regulatory floodway, no increase in flood levels during the base flood discharge will result; and
(3)
That the variance is the minimum necessary, considering the flood hazard, to afford relief.