Del Norte County Code
20 - Zoning
47 - Flood Damage Prevention
50 - Provisions for flood hazard reduction
The county shall obtain, review, and reasonably utilize the best base flood data available from any source: federal, state or other, such as high water mark(s), floods of record, or private engineering reports, in order to administer this chapter. In areas of special flood hazard, the following standards apply:
A. Standards of Construction. In all areas of special flood hazards the following standards are required:
a. All new construction and substantial improvements of structures, including
manufactured homes, shall be adequately anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
b. All manufactured homes shall meet the anchoring standards of subsection D of this section.
2. Construction Materials and Methods.
a. All new construction and substantial improvements of structures, including
manufactured homes, shall be constructed with flood resistant materials and utility equipment resistant to flood damage for areas below base flood elevation.
b. All new construction and substantial improvements, including manufactured homes, shall be constructed using methods and practices that minimize flood damage.
c. All new construction and substantial improvements, including manufactured homes, shall 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. All new construction and substantial improvements of structures, including
manufactured homes, shall be constructed, within Zones AB or AO, so that there are adequate drainage paths around structures on slopes to guide flood waters around and away from proposed structures.
3. Elevation and Floodproofing.
a. New construction and substantial improvements of any structure shall have the
lowest floor, including basement:
i. In AE, AB, AI-30 Zones, elevated to or above the base flood elevation.
ii. In an AO zone, elevated above the highest adjacent grade to a height equal to
or exceeding the depth number specified in feet on the FIRM, or elevated at least 2 feet above the highest adjacent grade if no depth number is specified.
iii. In an A zone, without BFE\'s specified on the FIRM (unnumbered A zone), elevated to or above the base flood elevation; as determined under Section 20.47.040.C.2.
Nomesidential structures may meet the standards in subsection (A)(3)(c) of this
section. Upon the completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered civil engineer or licensed land surveyor, and verified by the community building inspector to be properly elevated. Such certification and verification shall be provided to the floodplain administrator.
b. Nomesidential construction shall either be elevated in conformance with subsection (A)(3)(a) of this section or together with attendant utility and sanitary facilities:
i. Be floodproofed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water,
ii. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy, and
iii. Be certified by a registered professional engineer or architect that the standards of this subsection are satisfied. Such certifications shall be provided to the floodplain administrator.
c. All new construction and substantial improvements of structures with fully enclosed areas below the lowest floor (excluding basements) that are usable solely for parking of vehicles, building access or storage, and which are subject to flooding, 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 meet the following minimum criteria for non-engineered openings:
i. Have a minimum of two openings on different sides having a total net area of not
less than one square inch for every square foot of enclosed area subject to flooding.
ii. The bottom of all openings shall be no higher than one foot above grade.
iii. Openings may be equipped with screens, louvers, valves or other coverings or
devices, provided that they permit the automatic entry and exit of floodwaters, and
iv. Buildings with more than one enclosed area must have openings on exterior walls
for each area to allow flood water to directly enter, or
v. Be certified by a registered professional civil engineer or architect.
d. Manufactured homes shall also meet the standards in subsection D of this section.
4. Garages and low cost accessory structures.
a. Attached Garages
i. A garage attached to a residential structure, constructed with the garag floor slab below the BFE, must be designed to allow for the automatic entry of flood waters. See Section 20.47.050.A.3.c. Areas of the garage below the BFE must be constructed with flood resistant materials. See Section 20.47.050.A.2.
ii. A garage attached to a nonresidential structure must meet the above requirements or be dry floodproofed. For guidance on below grade parking areas, see FEMA Technical Bulletin TB6.
b. Detached garages and accessory structures.
i. "Accessory structures" used solely for parking (2 car detached garages or smaller) or limited storage (small, low-cost sheds), as defined in Section 20.47.020, may be constructed such that its floor is below the base flood elevation (BFE), provided the structure is designed and constructed in accordance with the following requirements"
1) Use of the accessory structure must be limited to parking or limited
2) The portions of the accessory structure located below the BFE must be
built using flood-resistant materials;
3) The accessory structure must be adequately anchored to prevent flotation,
collapse and lateral movement;
4) Any mechanical and utility equipment in the accessory structure must be elevated or floodproofed to or above the BFE;
The accessory structure must comply with floodplain encroachment provisions in Section
6) The accessory structure must be designed to allow for the automatic entry of flood waters in accordance with Section 20.47.050.A.3.c.
ii. Detached garages and accessory structures not meeting the above standards must be constructed in accordance with all applicable standards in Section
B. Standards for Utilities.
1. All new and replacement water supply and sanitary sewage systems shall be designed
to minimize or eliminate infiltration of floodwaters into the system and discharge from systems into floodwaters.
2. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
C. Standards for Subdivisions with Areas of Special Flood Hazard.
1. All preliminary subdivision proposals shall identify the flood hazard area and the
elevation of the base flood.
2. All final subdivision plans will provide the elevation of proposed structure(s) and
pads. If the site is filled above the base flood elevation, the lowest floor elevation, the
pad elevation, and the lowest adjacent grade as-built information for each structure
shall be certified by a registered civil engineer or licensed land surveyor and provided
as part of an application for a Letter of Map Revision based on Fill (LOMR -F) to the
3. All subdivision proposals and other proposed development shall be consistent with
the need to minimize flood damage.
4. All subdivision proposals and other proposed development shall have public utilities
and facilities such as sewer, gas, electrical and water systems located and constructed
to minimize flood damage.
All subdivisions and other proposed development shall provide adequate drainage to reduce exposure to flood hazards.
D. Standards for Manufactured Homes. All new and replacement manufactured homes and additions to manufactured homes shall:
1. Be elevated so that the lowest floor is at or above the base flood elevation; and
2. Be securely anchored to a permanent foundation system to resist flotation, collapse or
3. Be installed using methods and practices which minimize flood damage. These
regulations are in addition to applicable state and local requirements.
4. Within Zones VI-30, V, and VE on the community\'s Flood Insurance Rate Map,
meet the requirements of Section
All manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within Zones AI-30, AH,AE, VI-30, V, and VE on the community\'s Flood Insurance Rate Map that are not subject to the provisions ofSection20.47.050.D will be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement, and be elevated so that either the:
a. Lowest floor of the manufactured home is at or above the base flood elevation; or
b. Manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than 36 inches in height above grade. Upon the completion of the structure, the elevation of the lowest floor including basement shall be certified by a registered civil engineer or licensed land surveyor, and verified by the community building inspector to be properly elevated. Such certification and verification shall be provided to the Floodplain Administrator.
E. Floodways. Located within areas of special flood hazard established in Section 20.47.030B are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles, and erosion potential, the following provisions apply:
1. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge;
2. If subsection (E) (1) of this section is satisfied, all new construction and substantial
improvements shall comply with all other applicable flood hazard reduction provisions of this section.
F. Coastal High Hazard Areas. Within coastal high hazard areas established in Section
20.47.030B, the following standards shall apply:
1. All new residential and non-residential construction, including substantial improvement/damage, shall be elevated on adequately anchored pilings or columns
and securely anchored to such pilings or columns so that the bottom of the lowest
horizontal structural member of the lowest floor (excluding the pilings or columns) is
elevated to or above the base flood level. The pile or column foundation and structure attached thereto is anchored to resist flotation, collapse, and lateral movement due to the effects of wind and water loads acting simultaneously on all building components. Water loading values used shall be those associated with the base flood. Wind loading values shall be those required by applicable state or local building standards.
2. All new construction and other development shall be located on the landward side of
the reach of mean high tide.
3. All new construction and substantial improvements shall have the space below the lowest floor free of obstructions or constructed with breakaway walls as defined in Section 20.47.020. Such enclosed space shall not be used for human habitation and will be usable solely for parking of vehicles, building access or storage.
4. Fill shall not be used for structural support of buildings.
5. Man-made alteration of sand dunes which would increase potential flood damage is prohibited.
6. The floodplain administrator shall obtain and maintain the following records:
a. Certification by a registered engineer or architect that a proposed structure complies with subsection (F)(1) of this section;
b. The elevation (in relation to mean sea level) of the bottom of the lowest structural member of the lowest floor (excluding pilings or columns) of all new and substantially improved structures, and whether such structures contain a basement.
G. Standards for Recreational Vehicles.
1. All recreational vehicles placed on sites within Zones A, AI-30, AH, and AE on the community\'s Flood Insurance Rate Map will either:
a. Be on the site fewer than one hundred eighty consecutive days, and be fully licensed and ready for highway use a recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions; or
b. Meets the permit requirements of Section 20.47.040 of this chapter and the elevation and anchoring requirements for manufactured homes in subsection D of this section.
2. Recreational vehicles placed on sites within Zones VI-30, V, and VE on the community\'s Flood Insurance Rate Map will meet the requirements of subsections (F) and (G) (1) of this section.
(Ord. 95-15 (part), 1995, 2010)