§ 18.12.1703. Provisions for Flood Hazard Reduction.

(a)

Standards of Construction. In all flood hazard areas, the following standards are required:

(1)

Anchoring.  

a.

All new construction and substantial improvements shall be anchored to prevent floatation, collapse or lateral movement of the structure.

b.

All manufactured home units shall meet the anchoring standards of Section 18.12.1703(e).

(2)

Construction materials and methods.  

a.

All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.

b.

All new construction and substantial improvements shall use methods and practices that minimize flood damage.

c.

All elements that function as a part of the structure, such as furnace, hot water heater, air conditioner, etc., shall be elevated to one foot or more above the base flood elevation or depth number specified on the flood insurance rate map (FIRM).

d.

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

(3)

Elevation and floodproofing.  

a.

In zones A, A1—30, AH, and AE, new construction and substantial improvement of any structure shall have the bottom of the lowest floor beam or basement floor elevated to one foot or more above the base flood elevation. Nonresidential structures will meet the standards in paragraph d, below.

b.

New construction and substantial improvement to any structure in a zone AO shall have the bottom of the lowest floor beam or basement floor elevated from finish grade adjacent to the building at least one foot above the depth number specified on the flood insurance rate map (FIRM). If there is no depth number on the flood insurance rate map (FIRM), the bottom of the lowest floor beam or basement floor shall be elevated to a depth of at least two feet above the finished grade adjacent to the building. Nonresidential structures will meet standards in paragraph d, below.

c.

New construction and substantial improvement to any structure in a "shaded X" shall have the bottom of the lowest floor beam or basement floor elevated to at least one foot above the highest existing grade adjacent to the building, or one foot above the highest top of curb on the street adjacent to the property, as approved by the Floodplain Administrator. Nonresidential structures will meet standards in paragraph d, below.

d.

Nonresidential construction shall either be elevated in conformance with paragraphs a., b., or c., or together with attendant utility and sanitary facilities, be floodproofed as follows:

1.

Zone A: At least one foot above the base flood elevation.

2.

Zone AO: At least one foot above the depth number from finish grade adjacent to the building or where no depth number is given, two feet above the finish grade adjacent to the building.

3.

Shaded X: At least one foot above the highest existing grade adjacent to the building, or one foot above the highest top of curb on the street adjacent to the property, as approved by the administrator.

4.

Examples of floodproofing include, but are not limited to:

i.

Installation of watertight doors, bulkheads, and shutters.

ii.

Reinforcement of walls to resist water pressure.

iii.

Use of paints, membranes, or mortars to reduce seepage through walls.

iv.

Addition of mass or weight to the structure to resist floatation.

v.

Armor protection of all fill materials from scour and erosion.

5.

A registered professional engineer or architect shall develop and/or review plans for construction, and shall certify that the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effects of buoyancy.

e.

Manufactured homes shall meet the above standards and also the standards in Section 18.12.1703(e).

f.

In A1—30, AH and AE zones, all recreational vehicles must be fully licensed and highway ready. (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.) An acceptable option requires that the recreational vehicle be elevated on a permanent foundation so that the lowest portion of the floor will be elevated to or above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement. Methods of anchoring may include, but are not to be 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.

(b)

Standards for Alluvial Fans. Areas subject to alluvial fan flooding have irregular flow paths that result in erosion of existing channels and the undermining of fill material. Those areas are identified on the flood insurance rate map (FIRM) as AO and AH zones with velocities.

(1)

All structures must be securely anchored to minimize the impact of the flood and sediment damage.

(2)

All new construction and substantial improvements must be elevated on pilings, columns, or armored fill so that the bottom lowest floor beam is elevated at least one foot above the depth number.

(3)

All fill materials must be armored to protect the material from the velocity of the flood flow.

(4)

Provide adequate drainage paths around structures on slopes, to guide floodwaters around and away from proposed structures.

(5)

All proposals for subdivision development must provide a mitigation plan that identifies the engineering methods used to:

a.

Protect structures from erosion and scour caused by the velocity of the flood flow.

b.

Capture or transport flood and sediment flow through the subdivision to a point of deposition that will not create a health or safety hazard.

(6)

All manufactured homes shall be prohibited within the identified hazard area except within existing manufactured home parks or existing manufactured home subdivisions.

(c)

Standards for Utilities.  

(1)

Electrical, heating, ventilation, plumbing, and air-conditioning equipment and other service facilities shall be designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding.

(2)

On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.

(3)

All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system.

(4)

All new and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters or discharge from the systems into flood waters. Sanitary sewer and storm drainage systems for buildings that have openings below the base flood elevation shall be provided with automatic backflow valves or other automatic backflow devices that are installed in each discharge line passing through a building's exterior wall.

(d)

Standards for Subdivisions.  

(1)

In addition to the requirements for subdivisions set forth in NRS Chapter 278 and Chapter 18.10 of this Title, the following requirements apply:

a.

All tentative subdivision maps shall identify the flood hazard area, the limited flooding area, and the elevation of the base flood.

b.

All subdivision improvement plans shall identify the flood hazard area, the limited flooding area, the elevation of the base flood, the elevation of proposed structure(s), pads, and adjacent grade. If the site is filled above the base flood, the final pad elevation shall be certified by an engineer or surveyor and provided to the city.

c.

All subdivision proposals shall be consistent with the need to minimize flood damage.

d.

All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage to these utilities.

e.

All subdivision proposals shall demonstrate that adequate drainage will be provided to reduce exposure to flood damage as set forth in this section.

(e)

Standards for Manufactured Homes, Manufactured Home Parks, and Subdivisions.  

(1)

All new manufactured homes and additions to manufactured homes shall be set on a permanent foundation by anchoring the unit to resist flotation, collapse, or lateral movement by one of the following methods:

a.

By providing an anchoring system designed to withstand horizontal forces of 15 pounds per square foot and uplift forces of nine pounds per square foot, and vertical (down) loading as required by NRS 489.251.

b.

By the anchoring of the unit's system, designed to be in compliance to the U.S. Department of Housing and Urban Development, "Manufactured Home Construction and Safety Standards"; or

c.

By bolting the frame or undercarriage to a reinforced, permanent foundation such as a retaining wall or storm wall used to set the unit.

(2)

Adequate surface drainage and access for a hauler shall be provided.

(3)

All manufactured homes shall be placed on pads or lots elevated on compacted fill or on pilings so that the lowest floor of the mobile home is at least one foot above the base flood level. If elevated on pilings:

a.

The lots shall be large enough to permit steps;

b.

The pilings shall be placed in stable soil no more than ten feet apart; and

c.

A lateral reinforcement shall be provided for pilings taller than six feet above ground level.

(4)

No manufactured home shall be placed in a floodway.

(5)

Neither an existing manufactured home park nor an existing manufactured home subdivision shall be allowed to expand into a floodway.

(f)

Floodways.  

(1)

Located within flood hazard areas 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, any encroachment, including fill, new construction, substantial improvements, and other development is prohibited in the floodway.

(2)

If no floodway is identified, the permit applicant shall provide an engineering study for the project area that establishes a setback from the stream bank within which no encroachment of any new development will be allowed. Development occurring beyond the setback will be allowed only to the extent that the elevation of the base flood is not increased more than one foot at any point. The area reserved for conveyance between the stream channel and the setback shall be capable of discharging the base floodwaters without causing increased flood levels or velocities upstream or downstream.

(g)

Closed Intermittent Lakes, Restrictions. Development within watersheds contributing to closed basins and intermittent lakes shall not raise the base flood water surface elevation. Any development that would cause an expansion of the limits of the area designated as A, A1—30, AH, AE, and AO zones as shown on the FEMA maps shall require prior map amendment pursuant to Section 18.12.1701(h).

(Ord. No. 3153, § 1, 1-9-84; Ord. No. 3529, § 1, 6-22-87; Ord. No. 3765, §§ 2, 3, 2-27-89; Ord. No. 4162, § 2, 10-22-91; Ord. No. 4418, § 1, 8-23-94; Ord. No. 5978, § 1, 10-24-07; Ord. No. 6296, § 1, 6-5-13)

Cross reference

Subdivisions, Chapter 18.10; water service, Chapter 12.12; sewer service, Chapter 12.16.