Chapter 17.075 — FLOODPLAIN (F) OVERLAY ZONE

The floodplain (F) overlay zone is intended to restrict, prohibit or condition development within hazardous floodplain areas to assure that the type and intensity of use are consistent with the protection and preservation of people, property and significant resources. This zone includes those areas where grading of land may endanger public health and safety due to erosion and those areas possibly subject to flooding or inundation from stormwater.

A.1. Where permitted consistent with Section 17.075.020.4 below, any proposed development within the (F) overlay zone must submit proof at the time of application to the city, that their project complies with FEMA regulations for construction within one hundred year flood zone boundaries, and finished floor elevations are one foot above the projected one hundred-year flood line, or submit engineering data guaranteeing that the property is outside the one hundred year flood plain.

2. When base flood elevation data has not been provided in accordance with (A)(1), the city engineer 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 the standards of this overlay zone and provide the developer with an estimated based flood elevation. When uses are subject to potential flooding, but adequate data does not exist, the following criteria shall be used:

a. Single family use will be required to elevate the lowest floor of any structure to no less than two feet above natural grade when base flood data does not exist;

b. Multiple family (five or more) and commercial uses will be required to have all proposals establish the one hundred year base flood elevation before consideration of the preliminary plan for development.

B. Development in the one hundred-year floodplain shall not be permitted unless the applicant substantiates to the city that the development is protected from such flooding. No new fill, structure or other obstruction shall be placed or constructed within a Floodway unless a detailed hydrologic study has been prepared and approved by the city engineer ensuring that the structure will not obstruct, in any way, passing floodwaters, by such measures as elevated structures on piers, or pilings.

C. Public facilities and bridges that have to be built within the one hundred year floodplain zone shall be elevated to a minimum level of two feet above the one hundred-year floodlines.

D. No structures shall be located within the stream channel except (a) those structures necessary for flood control purposes which are found to be the only possible alternative to protect existing structures and property from flood hazards in the floodplain; (b) bridges when supports are located outside critical habitat areas; and (c) pipelines, when no alternative route is feasible; and (d) new underground utility transmission lines, when no alternative route is feasible.

E. No concrete channelization or other alterations of natural stream beds are permitted, except where necessary to protect existing facilities or bridges and where it is found that no other feasible alternative exists.

F. No new development shall be allowed in the floodplain overlay zone which will contribute to flood hazards on the same or other properties, or require flood control works for flood protection. Development within the floodplain overlay zone, in areas where a regulatory floodway is not designated, will only be permitted when the applicant has provided engineering technical data and facts which demonstrate that the cumulative effect of the proposed

development, when combined with all other 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; or establish a setback front the stream bank equal to five times the width of the stream at the top of the bank or twenty feet on each side from the top of the bank, whichever is greater, or where the development is built-up on pilings or where other similar measures are utilized which the city shall determine will not increase flood levels.

G. Within the Pismo Marsh/Meadow Creek Riparian and Creek Corridor, east of the railroad right of way, no additional structural development including diking, dredging, or filling is permitted below the forty-five feet contour line. Only those structures necessary to provide flood protection for existing structures, or to protect the public health and safety, and where no other feasible method of flood protection is possible, or the primary purpose of the project is the improvement of fish and wildlife habitat, shall be permitted. All permitted development which substantially alters any natural landform shall incorporate the best mitigation measures feasible to minimize the adverse environmental impacts of such development.

H. New development above the forty-five foot contour line north of Pismo Marsh/Meadow Creek shall be limited to that which is compatible with marsh preservation and shall be sited and designed to ensure that such development will not result in adverse impacts due to additional sediment, runoff and other disturbances.

I. Runoff from any project which drains to the marsh within Meadow Creek watershed or to Pismo Creek within the city limits shall not exceed the volume rate of flow or particulate content of runoff from the land in its natural and undisturbed state.

J. The city shall maintain and make available for public inspection the standards and criteria needed for flood insurance policies.

K. All new construction and substantial improvements within the floodplain when allowable by these standards shall be anchored to prevent flotation, collapse or lateral movement of the structure.

L. All new construction and substantial Improvements shall be constructed with materials and utility equipment resistant to flood damage, and use methods and practices that minimize flood damage.

M. Where elevating new non-residential construction and substantial improvements in conformance with the standards in this ordinance is infeasible, flood proofing to the base flood elevation must occur. Example, of flood proofing including, but are not limited to:

1. Installation of water tight doors, bulkheads and shutters;

2. Reinforcement of walls to resist water pressure;

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

4. Addition of mass or weight to structure to resist flotation;

5. Armor protection of all fill materials from scour and/or erosion;

6. Certification by a registered professional engineer or architect that the standards of this subsection are satisfied.

N. All new and replacement water supply and sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the system and discharge from systems into flood waters.

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

P. All new mobile homes and additions to mobile homes in existing parks subject to flooding shall be set on permanent foundation by anchoring the unit to resist flotation, collapse, or lateral movement by one of the following methods:

1. By providing an anchoring system designed to withstand horizontal forces of fifteen pounds per square foot and uplift forces of nine pounds per square foot; or

2. By the anchoring of the unit's system, designed to be in compliance with the Department of Housing and Urban Development Mobile Home Construction and Safety Standards; or

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

As set forth in the city's floodplain overlay zone regulations, certification meeting the standards above is required of the installer or state agency responsible for regulating the placement, installation, and anchoring of individual mobile home units.

Q. For areas within the floodplain but outside of the floodway, the following standards are required for (a) mobile homes not placed in mobile home parks or subdivisions, (b) new mobile home parks or subdivisions, (c) expansions to existing mobile home parks or subdivisions, and (d) repair, reconstruction, or improvements to existing mobile home parks or subdivisions that equals or exceeds fifty percent of the value of the streets, utilities, and pads before the

repair, reconstruction, or improvement commenced.

FLOOD CHANNEL SCHEMATIC DRAWING

U.S. DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT FEDERAL INSURANCE ADMINISTRATION

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

2. All mobile 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 a minimum of one foot above the base flood level. If elevated on pilings:

• a. The lots shall be large enough to permit steps, pilings, parking and other necessary accessory uses;

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

• c. Reinforcement shall be provided for pilings more than six feet above ground level.

• R. No mobile home shall be placed in a floodway, except in an existing mobile home park or existing mobile home subdivision.

S. Specific buffer setback standards for developments adjacent to Pismo Marsh/Meadow Creek and Pismo Creek are contained in the specific planning Area segments of the general plan/local coastal program land use plan and shall be applied as a condition of development.

T. All actions taken under this overlay zone shall be consistent with the relevant goals, policies and programs of the general plan/local coastal program land use plan.

U. All applicable criteria contained in Title 44, Emergency Management and Assistance, Chapter 1--Federal Emergency Management Agency, Section 60.3 (c), (d), and (e) if not included in the above regulations, is adopted by reference.