Napa County Municipal Code Art. IV Floodplain and Riparian Zone Management

A. When a structure or facility is being substantially improved as defined in Section 16.04.450 of this chapter, the entire structure or facility, including existing portions, must meet the conditions of this chapter. When less than substantial improvements are being done, the cost of these improvements will be accumulated for a ten year period. When the accumulated total cost of these improvements reaches fifty percent of the market value of the structure or the facility before initial improvement, then the structure or facility must meet the substantial improvement requirements of this chapter.

B. When an existing structure or facility complies with the requirements of this chapter, then all improvements to the existing structure or facility must also meet the requirements of this chapter.

C. All structural modifications and expansions shall conform to all applicable county land use zoning regulations, including but not limited to allowed uses, slope development limitations, and stream, yard, road and property line setbacks.

(Ord. 1307 § 1 (part), 2008)

A. All applicable standards of Title 44 of the U.S. Code of Federal Regulations at Section 60.3, the State and county building codes and this chapter must be met for any structure in a flood hazard area. The most restrictive regulation shall apply.

B. All new construction and substantial improvements shall be constructed with materials that are resistant to flood damage.

C. All new construction and substantial improvements shall be constructed using methods and practices that minimize the potential for and impact of flood damage.

D. All new construction and substantial improvements shall be constructed with electrical, heating, ventilation, plumbing and air conditioning equipment, and other service facilities, elevated at or above a level equal to the base flood elevation plus one foot of freeboard; or they shall be designed and installed to prevent water from accumulating within the components to resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding to the base flood elevation plus one foot of freeboard.

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

F. New and replacement sanitary sewage systems shall be designed to minimize or eliminate the potential for infiltration of floodwaters into the systems and for the discharge from the systems into floodwaters.

G. On-site waste disposal systems shall be located so as to avoid the potential for their impairment, or their causing contamination during flooding.

(Ord. 1307 § 1 (part), 2008)

(Ord. No. 1475, § 1, 4-19-2022)

A. All new construction and all substantial improvements shall be anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loading, including the effects of buoyancy.

B. All manufactured homes shall be anchored to resist flotation, collapse or lateral movement, by providing over-the-top ties and frame ties to ground anchors.

C. Over-the-top ties shall be provided at each of the four corners of the manufactured home, with two additional ties per side at intermediate locations, except that manufactured homes less than fifty feet long shall require only one additional tie per side.

D. Frame ties shall be provided at each corner of the home, with five additional ties per side at intermediate points, except that manufactured homes less than fifty feet long shall require only four additional ties per side.

E. All components of the anchoring system shall be capable of carrying a force of four thousand eight hundred pounds.

F. Any additions to the manufactured home, such as porches, cabanas and the like, shall be similarly anchored.

(Ord. 1307 § 1 (part), 2008)

A. All new subdivisions proposals and other proposed development, including proposals for manufactured home parks and subdivisions, greater than fifty lots or five acres, whichever is the lesser, shall:

1. Identify the Special Flood Hazard Areas (SFHA) and Base Flood Elevations (BFE).

2. Identify the elevations of lowest floors of all proposed structures and pads on the final plans.

3. If the site is filled above the base flood elevation, the following 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 floodplain administrator:

a. Lowest floor elevation.

b. Pad elevation.

c. Lowest adjacent grade.

B. All subdivision proposals and other proposed development shall be consistent with the need to minimize flood damage pursuant to all applicable flood regulations.

C. 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.

D. All subdivisions and other proposed development shall provide adequate drainage to reduce exposure to flood hazards.

(Ord. 1307 § 1 (part), 2008)

(Ord. No. 1413, § 2, 6-7-2016)

A. All manufactured homes that are placed or substantially improved, with Zones A, A1-30, AO, AH, and AE as designated on the FIRM, on sites located:

1. Outside of a manufactured home park or subdivision;

2. In a new manufactured home park or subdivision;

3. In an expansion to an existing manufactured home park or subdivision; or

4. In an existing manufactured home park or subdivision on a site upon which a manufactured home has incurred "substantial damage" as the result of a flood, shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to or above a level equal to the base flood elevation plus one foot of freeboard and be securely anchored to an adequately anchored foundation system to resist flotation collapse and lateral movement in accordance with Section 16.04.700.

B. All manufactured homes that are placed or substantially improved on sites located within Zones V1-30, V, and VE as designated on the FIRM will meet the requirements of subsection (A) of Section 16.04.710.

C. All manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within Zones A, A1—30, AO, AH, AE, V1—30, V, and VE as designated on the FIRM that are not subject to the provisions of subsection (A) of Section 16.04.710 will be elevated so that either:

1. The lowest floor of the manufactured home is at or above a level equal to the base flood elevation plus one foot of freeboard; or

2. The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are at or above a level equal to the base flood elevation plus one foot of freeboard, and securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement in accordance with Section 16.40.700.

(Ord. 1307 § 1 (part), 2008)

(Ord. No. 1475, § 2, 4-19-2022)

A. All recreational vehicles placed on sites within Zones A, A1-30, AO, AH, and AE as designated on the FIRM will either:

1. Be on the site for fewer than one hundred eighty consecutive days;

2. Be fully licensed and ready for highway use, meaning that each 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

3. Meet the permit requirements of this chapter and the elevation and anchoring requirements for manufactured homes in Section 16.04.710.

B. Recreation vehicles placed on sites within Zones V1-30, V and VE as designated on the FIRM will meet the requirements of subsection (A) of Section 16.04.715.

(Ord. 1307 § 1 (part), 2008)

New residential construction, and any substantial improvement and/or repairs of substantial damage to existing residential buildings and structures, within a special flood hazard area, shall have the lowest floor, including basement, elevated to or above a level equal to the base flood elevation plus one foot of freeboard. The floodplain administrator shall be provided the elevation relative to MSL of the lowest floor, including basement, certified by a registered professional engineer or surveyor on FEMA form 81-31 prior to issuance of a certificate of occupancy.

(Ord. 1307 § 1 (part), 2008)

(Ord. No. 1475, § 3, 4-19-2022)

New nonresidential construction and substantial improvement of any commercial, industrial or other nonresidential structure within a special flood hazard area shall:

A. Have the lowest floor, including basement elevated to or above a level equal to the base flood elevation plus one foot of freeboard. The floodplain administrator shall be provided the elevation relative to MSL of the lowest floor including basement certified by a registered professional engineer or surveyor on FEMA form 81-31 prior to issuance of a certificate of occupancy; or

B. Meet all of the following criteria:

1. Be floodproofed so that the structure is watertight with walls substantially impermeable to the passage of water below a level equal to the base flood elevation, plus one foot of freeboard, utilizing practices and principles described in technical bulletins TB 1-93, TB 3-93, and TB 7-93;

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

3. The floodplain administrator shall be provided the level of floodproofing certified by a registered professional engineer or architect on FEMA form 81-65 that the standards of this subsection are satisfied prior to issuance of a certificate of occupancy.

(Ord. 1307 § 1 (part), 2008)

A. All new construction and substantial improvements, 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 floodwaters.

B. Designs for meeting this requirement must either be certified by a registered professional engineer or architect, or meet or exceed the following minimum criteria:

1. Either 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, valves or other coverings or devices, provided that they permit the automatic entry and exit of floodwaters; or

2. Nonresidential structures may meet the floodproofing requirements of Section 16.04.730 of this code.

(Ord. 1307 § 1 (part), 2008)

The following restrictions shall apply to all proposed activities within any riparian zone:

A. The proposed activity will not, with regard to the riparian zones along a channel, remove more than the following:

1. A native tree eighteen inches DBH per one hundred linear feet of riparian zone on each side of the floodplain, or

2. Three native trees twelve inches DBH per one hundred linear feet of riparian zone on each side of the floodplain, or

3. Six native trees six inches DBH per one hundred linear feet of riparian zone on each side of the floodplain, or

4. Five hundred square feet of vegetation in riparian zones beyond ten feet from the top of the bank, or

5. The temporary removal of a portion of riparian vegetation not more than fifteen feet wide beyond ten feet from the top of the bank, where replanting of such strip is a part of the project; and

B. The proposed activity will not involve the locating of any facility or structure within ten feet from the top of the bank; and

C. Will not result in a cut or fill slope that would remain unprotected by slope reseeding and bank stabilization replanting at the end of the project, thereby making the slope susceptible to erosion.

(Ord. 1307 § 1 (part), 2008)

No structure or facility shall be constructed, located, extended, converted or altered without full compliance with the provisions of this chapter as it may be amended from time to time, and all other applicable regulations.

(Ord. 1307 § 1 (part), 2008)

Neither the issuance of a permit nor compliance with the conditions thereof, nor with the provisions of this chapter, shall act to relieve any person from any responsibility otherwise imposed by law; nor shall the issuance of any permit hereunder serve to impose any liability or obligation upon the county, its officers or employees, for any injury or damage to persons or property. A permit issued pursuant to this chapter shall not relieve the permittee of the responsibility of securing and complying with all other permit requirements and procedures which may be required by any other law, rule or regulation.

(Ord. 1307 § 1 (part), 2008)

The degree of flood protection required by this chapter is considered reasonable for regulatory purposes, and is based on scientific and engineering considerations. Larger floods can and will occur on rare occasions. Flood heights may also be increased by man-made or natural causes. This chapter is not intended as, and does not imply nor represent a guarantee that land outside the base floodplain areas, or uses permitted within such areas, will be free from flooding or flood damages. This chapter shall not create any liability on the part of the county, any officer or employee thereof, or the Federal Insurance Administration, for any flood damages that result from reliance on this chapter or any administrative decision lawfully made thereunder.

(Ord. 1307 § 1 (part), 2008)

In addition to any other procedure or remedy provided by law, if work coming within the purview of this chapter is performed without a valid permit having first been obtained, the floodplain administrator, or his authorized representative, may personally serve a written notice on the permittee, or mail such notice, postage prepaid and return receipt requested, to the address at which, in the opinion of the floodplain administrator, such notice is most likely to be received by the permittee. Such notice shall state the nature of the violation, and shall direct the permittee to immediately cease operations. Such notice shall also direct that the permittee have plans and specifications prepared in a form acceptable to the floodplain administrator in order to rectify the situation. Following approval by the floodplain administrator of the plans, the permittee shall abate the condition constituting the violation within ten days after notice is received. Such notice shall also provide that if the permittee fails to abate the violation, the county may do so, in which event the permittee shall be liable for all cost of such abatement, including but not limited to reimbursement for staff time and reasonable attorney's fees.

(Ord. 1307 § 1 (part), 2008)

The floodplain administrator shall notify the owner in writing of a violation of this chapter by means of a compliance letter directing the owner to remedy the violation. If the owner does not remedy the violation, in accordance with the notice described in Section 16.04.800 and pursuant to Section 16.04.400, the floodplain administrator shall so report to the board; and if directed by the board, the floodplain administrator shall abate the violation. Such abatement may be accomplished either by county work forces or by others under contract with the county. The permittee involved shall be liable to the county for all costs incurred in such abatement, including but not limited to reasonable attorney's fees.

(Ord. 1307 § 1 (part), 2008)

If it appears to the floodplain administrator that an emergency exists because of a violation of the provisions of this chapter, then without following the procedures established by Sections 16.04.800 and 16.04.810 of this chapter, the floodplain administrator may, with approval of the board, order all work necessary to remove, abate or mitigate the emergency. The floodplain administrator may do the work with county work forces, or may contract to have such work done. In either case, the floodplain administrator shall keep a record of the costs of the work and charge such cost to the owner of the parcel involved, who shall be obligated to reimburse the county.

(Ord. 1307 § 1 (part), 2008)

The cost of any work done by the county pursuant to this chapter shall be repaid to the county by the owner of the parcel where the violation occurred. If the charges or costs incurred are not paid within sixty days after notice thereof is mailed to the owner, the amount of the charge, plus accrued interest at the rate of seven percent per year from the date of mailing of the charges, shall be added to the next regular tax bill sent to the owner by the county tax collector, and shall be collected in the manner fixed by law for the collection of taxes generally; or, in the alternative, recovery may be had through civil action.

(Ord. 1307 § 1 (part), 2008)

It shall be unlawful and a misdemeanor for any person to perform any work described in Section 16.04.560 of this chapter without a valid permit first having been obtained.

(Ord. 1307 § 1 (part), 2008)