Chapter 16.52 — FLOOD HAZARD REGULATIONS

The city council finds that:

(a) The National Flood Insurance Act of 1968, as amended, and federal regulations promulgated thereunder, require the city to adopt certain flood hazard regulations in conformance with standards established by the Flood Insurance Administration;

(b) The flood hazard areas of the city are subject to periodic inundation which may result in loss of life and property, impose health and safety hazards, disruption of commerce and governmental services, extraordinary public expenditures for flood protection and relief, and impairment of the tax base, all of which adversely affect the public health, safety, and general welfare; and

(c) These flood losses are often caused by the cumulative effect of obstructions in areas of special flood hazards which increase flood heights and velocities, and when inadequately anchored, damage uses in other areas. Uses that are inadequately floodproofed, elevated or otherwise

protected from flood damage also contribute to the flood loss.

(Ord. 3158 § 1 (part), 1979)

This chapter is adopted in order to comply with the National Flood Insurance Program (NFIP) (implementing the National Flood Act of 1968, as amended), and federal regulations adopted thereunder for the purpose of promoting public health, safety and general welfare and to minimize public and private losses due to flood conditions in specific areas by provisions designed:

(a) To protect human life and health;

(b) To minimize the need for costly flood control projects, and to supplement the effectiveness of such projects;

(c) To minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;

(d) To minimize prolonged business interruptions;

(e) To minimize damage to public facilities and utilities such as water and gas mains, electric, telephone and sewer lines, streets and bridges located in areas of special flood hazard;

(f) To help maintain a stable tax base by providing for the sound use and development of areas of special flood hazard so as to minimize future blight areas;

(g) To ensure that potential buyers are notified that property is in an area of special flood hazard; and

(h) To ensure that those who occupy the areas of special flood hazard assume responsibility for their actions.

(Ord. 4557 § 1, 1999: Ord. 3795 § 1, 1988: Ord. 3158 § 1 (part), 1979)

In order to accomplish its purposes, this chapter includes methods and provisions for:

(a) Restricting or prohibiting uses which are dangerous to health, safety, and property due to water or erosion hazards, or which result in damaging increases in erosion or in flood heights or velocities;

(b) Requiring that uses vulnerable to floods, including facilities which serve such uses, be protected against flood damage at the time of initial construction;

(c) Controlling the alteration of natural floodplains, stream channels, and natural protective barriers, which help accommodate or channel floodwaters;

(d) Controlling filling, grading, dredging, and other development which may increase flood damage; and

(e) Preventing or regulating the construction of flood barriers which will unnaturally divert floodwaters or which may increase flood hazards in other areas.

(Ord. 3158 § 1 (part), 1979)

(a) The definitions contained hereafter shall govern the interpretation of the terms defined for the purposes of this chapter, except where the context clearly requires otherwise. Words used in this chapter and not defined in this section shall be interpreted so as to give them the meaning they have in common usage and to give this chapter its most reasonable application.

(1) "Appeal" means a request for a review of the floodplain administrator's interpretation of any provision of this chapter or a request for a variance.

(2) "Area of shallow flooding" means a designated AO or AH zone on the Flood Insurance Rate Map. The base flood depths range from one to three feet; a clearly defined channel does not exist; the path of flooding is unpredictable and indeterminate; and velocity flow may be evident.

(3) "Area of Special Flood Hazard." See "Special flood hazard area."

(4) "Base flood" or "one hundred year flood" means the flood having a one percent chance of being equaled or exceeded in any given year.

(5) “Base flood elevation (BFE)” means elevation of flooding, including wave height, relative to the National Geodetic Vertical Datum (NGVD), North American Datum (NAVD) or other datum specified on the Flood Insurance Rate Map (FIRM) having a 1% chance of being equaled or exceeded in any given year.

(6) “Basement” means any area of the building having its floor subgrade (below ground level) on all sides.

(7) “Breakaway walls” means any type of walls, whether solid or lattice, and whether constructed of concrete, masonry, wood, metal, plastic or any other suitable building material which is not part of the structural support of the building and which is designed to break away under abnormally high tides or wave action without causing any damage to the structural integrity of the building on which they are used or any buildings to which they might be carried by floodwaters. A breakaway wall shall have a safe design loading resistance of not less than ten and no more than twenty pounds per square foot. Use of breakaway walls must be certified by a registered engineer or architect and shall meet the following conditions:

(A)  Breakaway wall collapse shall result from a water load less than that which would occur during the base flood; and

(B) The elevated portion of the building shall not incur any structural damage due to the effects of wind and water loads acting simultaneously

in the event of the base flood.

(8) “Coastal high hazard area” is the area subject to high velocity waters, including coastal and tidal and inundation or tsunamis. The area is designated on the Flood Insurance Rate Map as Zone V1 - V30, VE or V.

(9) “Design Flood Elevation (DFE)” means elevation of the design flood, including wave height, relative to the datum specified on the community's flood hazard map.

(10) “Development” means 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 bulk storage of equipment or materials.

(11) “Dry floodproofing” means a combination of measures that results in a structure, including the attendant utilities and equipment, being watertight with all elements substantially impermeable and with structural components having the capacity to resist flood loads.

(12) “Flood” or “Flooding” means a general and temporary condition of partial or complete inundation of normally dry land areas from (A) the overflow of floodwaters, (B) the unusual and rapid accumulation or runoff of surface waters from any source, and/or (C) the collapse or subsidence of land along the shore of a lake or other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels or suddenly caused by an unusually high water level in a natural body of water, accompanied by a severe storm, or by an unanticipated force of nature, such as flash flood or an abnormal tidal surge, or by some similarly unusual and unforeseeable event which results in flooding.

(13) “Flood Boundary and Floodway Map” means the official map on which the Federal Emergency Management Agency or Federal Insurance Administration has delineated both the areas of flood hazard and the floodway.

(14) “Flood control project” means a dam or barrier design and constructed to keep water away from or out of a specific area, including but not limited to levees, floodwalls and channelization.

(15) “Flood Insurance Rate Map” means the official map on which the Federal Emergency Management Agency or Federal Insurance Administration has delineated both the areas of special flood hazard and the risk premium zones applicable to the community.

(16) “Flood Insurance Study” means the official report provided by the Federal Insurance Administration that includes flood profiles, the Flood Insurance Rate Map, the Flood Boundary and Floodway Map, and the water surface elevation of the base flood.

(17) “Floodplain” or “flood-prone area” means any land area susceptible to being inundated by water from any flood.

(18) “Floodplain management” means the operation of an overall program of corrective and preventive measures for reducing flood damage, including but not limited to emergency preparedness plans, flood control works and floodplain management regulations.

(19) “Floodplain management regulations” means zoning ordinances, subdivision regulations, building codes, health regulations, special purpose ordinances (such as floodplain ordinance, grading ordinance and erosion control ordinance) and other applications of police power. The term describes such State of California or local regulations in any combination thereof, which provide standards for the purpose of flood damage prevention and reduction.

(20) “Floodproofing” means any combination of structural and nonstructural additions, changes or adjustments to non-residential structures which reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, structures and their contents.

(21) “Floodway” or “regulatory floodway” means 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 one foot.

(22) “Functionally dependent use” means a use which has an intended purpose that cannot be performed, unless it is located or carried out in close proximity to water. The term includes only docking facilities, port facilities that are necessary for the loading and unloading of cargo or passengers, and shipbuilding and ship repair facilities, but does not include long-term storage or related manufacturing facilities.

(23) “Highest adjacent grade” means the highest natural elevation of the ground surface prior to construction next to the proposed foundations of a structure.

(24) “Historic structure” means any structure that is listed individually in the National Register of Historic Places or in the State of California Register of Historical Resources or any structure that is listed individually in the current edition of the Palo Alto Master List of Structures on the Historic Inventory in Category 1 “Exceptional Building” or Category 2 “Major Building” or any structure that has been certified by the Keeper of the National Register as contributing to the historical significance of a registered historic district.

(25) “Hydrodynamic loads” means loads imposed on an object by water flowing against and around it.

(26) “Hydrostatic loads” means loads imposed on an object by standing mass of water.

(27) “Letter of map change (LOMC)” means an official determination issued by FEMA that amends or revises an effective Flood Insurance Rate Map or Flood Insurance Study through a Letter of Map Amendment (LOMA), Letter of Map Revision (LOMR) or Letter of Map Revision based on fill (LOMR-F).

(A)  “Letter of Map Amendment (LOMA)”: An amendment based on technical data showing the property was incorrectly included in a

designated special flood hazard area. A LOMA amends the current effective Flood Insurance Rate Map and establishes that a specific property, portion of a property, or structure is not located in a special flood hazard area.

(B)  “Letter of Map Revision (LOMR)”: A revision based on technical data that may show changes to flood zones, flood elevations, special flood

hazard area boundaries and floodway delineations, and other planimetric features.

(C)  “Letter of Map Revision (LOMR-F)”: A determination that a structure or parcel of land has been elevated by fill above the base flood

elevation and is, therefore, no longer located within the special flood hazard area. In order to qualify for this determination, the fill must have been permitted and placed in accordance with the community's floodplain management regulation.

(D) “Conditional Letter of Map Revision (CLOMR)”: A formal review and comment as to whether a proposed flood protection project or other project complies with the minimum NFIP requirements for such projects with respect to delineation of special flood hazard area. A CLOMR does not revise the effective Flood Insurance Rate Map or Flood Insurance Study, upon submission and approval of certified as-built documentation, a Letter of Map Revision may be issued by FEMA to revise the effective FIRM.

(28) “Lowest floor” means the lowest floor of the lowest enclosed area, including basement.

(A) An unfinished or flood resistant enclosure below the lowest floor that is usable solely for the 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 it conforms to the applicable non-elevation design requirements, including but not limited to:

  (1) The standard set forth in subdivision (3) of subsection (c) of Section16.52.130;

  (2) The anchoring standards set forth in subdivision (1) of subsection (a) of Section16.52.130;

  (3) The construction materials and methods standards set forth in subsection (b) of Section16.52.130; and

  (4) The standards for utilities set forth in Section16.52.140.

(B)  For residential structures, all subgrade enclosed areas are prohibited as they are considered to be basements. This prohibition includes

below-grade garages, storage areas and subfloor crawl spaces, except existing below-grade subfloor crawl spaces meeting the standards set forth in subsection (d) of Section 16.52.130.

(29) “Manufactured home” means 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 it is attached to the required utilities. The term does not include a recreational vehicle.

(30) “Manufactured home park or subdivision” means a parcel (or contiguous parcels) of land divided into two or more manufactured home lots for sale or rent.

(31) “Market value of the structure” means that value of a structure determined by estimating the cost to replace the structure in a new condition and adjusting that cost figure by the amount of depreciation which has accrued since the structure was constructed. The cost of replacement of the structure shall be based on a square foot cost factor determined by reference to a building cost estimating guide recognized by the building construction industry, as approved by the floodplain administrator. The amount of depreciation shall be determined by taking into account the age and physical deterioration of the structure and functional obsolescence, as approved by the floodplain administrator, but shall not include economic or other forms of external obsolescence. The use of replacement costs or accrued depreciation factors different from those contained in recognized building cost estimating guides may be approved at the discretion of the floodplain administrator only if such factors are included in a report prepared by an independent professional appraiser and supported by a written explanation of the differences.

(32) “Mean sea level” means, for purposes of the National Flood Insurance Program, 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.

(33) “New construction,” for floodplain management purposes, means structures for which the “start of construction” commenced on or after the effective date of floodplain management regulations adopted by this community, and includes any subsequent improvements to such structures.

(34) “Person” means an individual or his agent, firm, partnership, association or corporation, or agent of the aforementioned groups, or the State of California or its agencies or political subdivisions.

(35) “Recreational vehicle” means a vehicle which:

(A)  Is built on a single chassis;

(B)  Measures 400 square feet or less at its largest or widest horizontal projection;

(C)  Is designed to be self-propelled or permanently towable by a small truck;

(D)  Is designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, seasonal use camping or travel;

and

(E)  Incorporates a vehicle that is defined by the State of California as a camp trailer, camper, fifth-wheel travel trailer, or house car.

(36) “Remedy a violation” means to bring the structure or other development into compliance with the State of California or local floodplain management regulations, or, if this is not possible, to reduce the impacts of its noncompliance. Ways that impacts may be reduced include protecting the structure or other affected development from flood damages, implementing the enforcement provisions of this chapter or otherwise deterring future similar violations, or reducing federal or State of California financial exposure with regard to the structure or other development.

(37) “Riverine” means relating to, formed by, or resembling a river (including tributaries), stream, or brook.

(38) “Sand dunes” means naturally occurring accumulations of sand in ridges or mounds landward of the beach.

(39) “Special flood hazard area (SFHA)” means an area having special flood or flood-related erosion hazards, and shown on the Flood Insurance Rate Map as Zone A, AO, Al - A30, AE, AH, V1 - V30, VE or V.

(40) “Start of construction” includes substantial improvement and other proposed new development, and means the date on which the building permit was issued, provided the actual start of construction, repair, reconstruction, rehabilitation, addition, placement, or other improvement commenced within 180 days from the date of issuance of the permit. 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 stage 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 not part of the main structure. For a substantial improvement, the actual start of construction means the first alteration of any wall, ceiling, floor, or other part of a structure, whether or not that alteration affects the external dimensions of the structure.

(41) “Structure” means a walled and roofed building, including but not limited to a gas or liquid storage tank, that is principally above ground, as well as a manufactured home.

(42) “Substantial damage” means damage of any origin sustained by a structure, whereby the cost of restoring the structure to its original damage-free condition would equal or exceed fifty percent of the market value of the structure before the damage occurred.

(43) “Substantial improvement” means any reconstruction, rehabilitation, addition, or other proposed new development of a structure, the cost of which equals or exceeds fifty percent of the market value of the structure before the start of construction of the improvement. This term includes a structure which has incurred substantial damage, regardless of the actual repair work to be performed.

The term shall not include:

(A) Any project, or any portion of a project, for improvement of a structure undertaken in response to a finding by the local code enforcement

official that there are existing violations of State of California or local health, sanitary, or safety code specifications which render the structure unfit for human occupancy; or

(B) Any alteration of an historic structure, provided that the alteration will not result in the termination of a structure’s continued designation as

an historic structure; or

(C) Any project, or any portion of a project, for improvement of a structure that is required to comply with the Americans with Disabilities Act of 1990 (42 U.S.C. Section 12101 et.seq.).

(44) “Variance” means a grant of relief from the requirements of this chapter which permits construction in a manner that would otherwise be prohibited by this chapter.

(45) “Violation” means 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 in this chapter is presumed to be in violation until such time as that documentation is provided.

(46) “Wet floodproofing” means a floodproofing method that relies on the use of flood damage-resistant materials and construction techniques in areas of a structure that are below the elevation required by this standard by intentionally allowing those areas to flood.

(Ord. 5566 § 3, 2022: Ord. 4824 § 1, 2004: Ord. 4557 § 2, 1999: Ord. 3795 § 2, 1988: Ord. 3158 § 1 (part), 1979)

This chapter shall apply to all areas of special flood hazards within the jurisdiction of the city.

(Ord. 3158 § 1 (part), 1979)

The areas of special flood hazard identified by the Federal Insurance Administration of the Federal Emergency Management Agency in the Flood Insurance Study, dated June 2, 1999, the accompanying Flood Insurance Rate Map, and all subsequent amendments and revisions thereto, are hereby adopted by reference and declared to be a part of this ordinance. The areas of special flood hazard that are identified in the Flood Insurance Study and depicted in the attendant mapping are the minimum surface areas of land to which the ordinance codified in this chapter will apply. The Flood Insurance Study may be supplemented by a study or studies for other areas which will allow the implementation of this ordinance and which are recommended to the city council by the floodplain administrator. The Flood Insurance Study and the Flood Insurance Rate Map shall be made available for inspection at the department of public works of the City of Palo Alto, 250 Hamilton Avenue, Palo Alto, California.

(Ord. 4557 § 3, 1999: Ord. 3795 § 3, 1988: Ord. 3158 § 1 (part), 1979)

No structure or land shall hereafter be constructed, located, extended, converted or altered without full compliance with the terms of this chapter and other applicable regulations. Violations of the provisions of this chapter by failure to comply with any of its requirements (including violations of conditions and safeguards established in connection with conditions) shall constitute a misdemeanor. Nothing herein shall prevent the city from taking such lawful action as is necessary to prevent or remedy any violation.

(Ord. 3795 § 4, 1988: Ord. 3158 § 1 (part), 1979)

A community's base flood elevations may increase or decrease resulting from physical changes affecting flooding conditions. As soon as practicable, but not later than six months after the date such information becomes available, the City shall notify FEMA of the changes by submitting technical or scientific data. Such submission is necessary so that, upon confirmation of those physical changes affecting flooding conditions, risk premium rates and flood plain management requirements will be based upon current data.

(Ord. 5566 § 4, 2022)

This chapter is not intended to repeal, abrogate, or impair any existing easements, covenants, or deed restrictions. However, where this chapter and another ordinance, easement, covenant, or deed restriction conflict or overlap, whichever imposes the more stringent restrictions shall prevail.

(Ord. 3158 § 1 (part), 1979)

In the interpretation and application of this chapter, all provisions shall be:

(a) Considered as minimum requirements;

(b) Liberally construed in favor of the governing body; and

(c) Deemed neither to limit nor repeal any other powers granted under provisions of law.

(Ord. 3158 § 1 (part), 1979)

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 than those upon which these regulations are based can and will occur on rare occasions. Flood heights may be increased by manmade or natural causes. This chapter does not imply that land outside the areas of special flood hazards or uses permitted within such areas will be free from flooding or flood damages. This chapter shall not create liability on the part of the city, any officer or employee thereof, the State of California, or the Federal Insurance Administration of the Federal Emergency Management Agency, for any flood damages that result from reliance on this chapter or any administrative decision lawfully made thereunder. All persons performing any construction within the city should and are advised to determine to their own satisfaction the level of flood protection in addition to that required by this chapter necessary or desirable to insure protection of their property.

(Ord. 4557 § 4, 1999: Ord. 3158 § 1 (part), 1979)

A development permit shall be obtained before construction or development begins within any area of special flood hazard established by Section

Applications for a development permit shall be made with the chief building official on forms consistent with those provided by the

floodplain administrator and upon such application as may be specified by the chief building official. In the case of any construction or development for which a permit such as a building, electrical, plumbing or grading permit is otherwise required by this title, that permit shall constitute the development permit for the project and no separate application shall be required. In such event, the provisions of this chapter shall be complied with and the course of issuance of such permit and such permit shall be conditioned upon such provisions as may be required by this chapter. In addition to any other requirements, the chief building official may require the submission of such materials as are necessary to insure compliance with the provisions of this chapter, which may include, but shall not be limited to: plans in duplicate drawn to scale showing the nature, location, dimensions and elevations of the area in question; existing or proposed structures, fill, storage of materials, drainage facilities; and the location of the foregoing. In all cases, the following information shall be required:

(a) A site plan, including but not limited to:

(1) For all proposed structures, spot ground elevations at building corners and twenty-foot or smaller intervals along the foundation footprint, or one-foot contour elevations throughout the building site;

  (2) The proposed locations of water supply, sanitary sewers, and utilities; and

  (3) The base flood elevation from the Flood Insurance Study or the Flood Insurance Rate Map, or both, to the extent available;

(b) The foundation design details, including but not limited to:

  (1) The proposed elevation in relation to mean sea level, of the lowest floor, including basement, of all structures;

  (2)  For a crawl-space foundation, the location and total net area of foundation openings as required in this ordinance and applicable Federal

Emergency Management Agency technical bulletins, including but not limited to, TB 1 and TB 7; and

  (3)  For foundations placed on fill, the location and height of the fill, and compaction requirements (compacted to ninety-five percent using the

Standard Proctor Test method);

(c)  Proposed elevation in relation to mean sea level to which any nonresidential structure will be floodproofed, as required in subdivision (3) of

subsection (c) of Section 16.52.130 and applicable Federal Emergency Management Agency Technical Bulletins, including but not limited to TB 3;

(d)  All appropriate certifications listed in subsection (d) of Section16.52.120; and

(e) A description of the extent to which any watercourse will be altered or relocated as a result of the proposed development.

(Ord. 5566 § 5, 2022: Ord. 4557 § 5, 1999: Ord. 3795 § 5, 1988: Ord. 3158 § 1 (part), 1979)

The city engineer is appointed to administer and implement this chapter by granting or denying development permits in accordance with its provisions, and shall be known as the floodplain administrator. The duties and responsibilities of the floodplain administrator shall include but not be limited to the following:

(a) Permit review.

(1) Review all development permits to determine that the permit requirements of this chapter have been satisfied;

(2) All other required state and federal permits have been obtained;

(3) The site is reasonably safe from flooding; and

(4) The proposed development does not adversely affect the carrying capacity of areas where base flood elevations have been determined but a floodway has not been designated. For purposes of this chapter, "adversely affects" means that the cumulative effect of the proposed development when combined with all other existing and anticipated development will increase the water surface elevation of the base flood more than one foot at any point.

(b) Use of Other Base Flood Data. When base flood elevation data have not been provided, in accordance with Section16.52.060, the floodplain administrator shall obtain, review, and reasonably utilize any base flood elevation and floodway data available from a federal, state or other source, in order to administer the standards of construction, standards for utilities, standards for subdivisions, standards for manufactured homes, provisions relating to floodways and provisions relating to coastal high hazard areas provided in this chapter.

(c) Whenever a watercourse is to be altered or relocated:

(1) Notify adjacent communities, the Santa Clara Valley Water District, and the California Department of Water Resources prior to such alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration of the Federal Emergency Management Agency; and

(2) Require that the flood-carrying capacity of the altered or relocated portion of the watercourse is maintained.

(d) Obtain and maintain for public inspection and make available as needed:

(1) The certifications required in subdivision (1) of subsection (c) of Section16.52.130 (Lowest floor elevations);

(2) The certification required in paragraph (C) of subdivision (2) of subsection (c) of Section16.52.130 (Elevation or floodproofing of nonresidential structures);

(3) The certification required in paragraph (B) of subdivision (3) of subsection (c) of Section16.52.130 (Wet floodproofing standard);

(4) The certified elevation required in subsection (b) of Section 16.52.150 (Subdivision standards);

(5) The certification required in subsection (a) of Section 16.52.170 (Floodway encroachments); and

(6) The information required in subsection (f) of Section16.52.180 (Coastal construction standards).

(e) Make interpretations where needed, as to the exact location of the boundaries of the areas of special flood hazards. Where there is an apparent conflict between a mapped boundary and the actual field conditions, grade and base flood elevations shall be used to determine the boundaries of the special flood hazard area. The person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation as provided hereinafter.

(f) Take action to remedy violations of this chapter as specified in Section16.52.070.

(Ord. 4557 § 6, 1999: Ord. 3795 § 6, 1988: Ord. 3158 § 1 (part), 1979)

In all areas of special flood hazards the following standards are required:

(a)  Anchoring.

  (1)  All new construction and substantially improved structures shall be anchored to prevent flotation, collapse or lateral movement of the

structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.

  (2)  All manufactured homes shall meet the anchoring standards of Section 16.52.160.

(b) Construction Materials and Methods.

  (1)  All new construction and substantially improved structures shall be constructed with flood-resistant materials as specified in applicable

Federal Emergency Management Agency Technical Bulletins, including but not limited to TB 2, and utility equipment resistant to flood damage.

  (2)  All new construction and substantially improved structures shall be constructed using methods and practices that minimize flood damage.

  (3)  All new construction and substantially improved structures 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.

  (4)  Require within Zones AH or AO, adequate drainage paths around structures on slopes to guide floodwaters around and away from

proposed structures.

(c)  Elevation and Floodproofing.

  (1)  In residential new construction and substantial improvement of any residential structure, the lowest floor, including basement:

    (A)  In an AO zone, shall be elevated to a height above the highest adjacent grade of not less than the depth number specified in feet on the

Flood Insurance Rate Map plus 1 foot, or not less than 3 feet above the highest adjacent grade if no depth number is specified;

    (B)  In an A zone, shall be elevated at least two feet above the highest adjacent grade if no depth number is specified or one foot above the

base flood elevation, whichever is higher; or

   (C)  In all other zones, including Coastal A zones shall be elevated at least one foot above the base flood elevation.

   (D) Basement floors that are below grade on all sides shall be elevated to or above base flood elevation plus 1 foot, or design flood

elevation, whichever is higher.

    (E)  Garages and carport floors shall comply with one of the following:

          (i)  They shall be elevated to or above the elevations required above in (A), (B) and (C) or

           (ii)  They shall be at or above grade on all but one side of the structure and allow the automatic flow of floodwater into and out of the

garage or carport. Where a garage or carport shall solely be used parking, building access or storage.

Upon the completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered professional engineer or surveyor, and verified by a community official to be properly elevated. Such certification and verification shall be provided to the floodplain administrator.

(2) Nonresidential new construction and any substantially improved nonresidential structure shall either be elevated to conform with subdivision (1) of this subsection (c) or, together with attendant utility and sanitary facilities:

    (A)  Shall be floodproofed below the minimum elevation required in subdivision (1) above so that the structure is watertight with walls

substantially impermeable to the passage of water;

    (B)  Shall possess structural components capable of resisting hydrostatic and hydrodynamic loans and effects of buoyancy; and

   (C)  Shall be certified by a registered professional engineer that the standards of this subdivision are satisfied. The certification shall be

provided to the floodplain administrator.

   (D)  Shall provide a flood emergency plan that includes maintenance and operation requirements. The plan shall be approved by the

floodplain administrator. Plans shall be recorded as a covenant.

  (3)  All new construction and substantially improved structures, with fully enclosed areas below the lowest floor (excluding basements) that

are usable solely for the 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. Designs for meeting this requirement shall comply with the guidelines set forth in the applicable Federal Emergency Management Agency technical bulletins, including but not limited to TB 1 and TB 7, and shall meet or exceed the following minimum criteria:

    (A)  Possess a minimum of two openings on different sides of each enclosed area. If a building has more than one enclosed area, each area

shall have openings with the total net area of nonengineered openings of not less than one square inch for every square foot of enclosed area, where the enclosed area is measured on the exterior of the enclosure walls. The bottom of all openings shall be no higher than one foot above the higher of the final interior grade or floor and the finished exterior grade immediately under each opening. Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwaters into and out of the enclosed areas and shall be accounted for in the determination of the net open area; or

    (B) Be certified by a registered professional engineer or architect. Construction documents shall include a statement by a registered design

professional that the design of the openings will provide for equalization of hydrostatic flood forces on exterior walls by allowing for the automatic entry and exit of floodwaters as specified on Section 2.7.2.2 of ASCE 24.

   (C)  Openings shall be not less than 3 inches in any direction in the plane of the wall.

   (D)  Openings shall be permitted to be installed in doors and windows; doors and windows without installed openings do not meet the

requirement of this section.

  (4)  Manufactured homes shall also meet the standard in Section 16.52.160.

(d) Existing Residential Below Grade Subfloor Crawl Spaces. Notwithstanding the provisions of subsection (c)(1) for existing residential structures, existing below-grade subfloor crawl spaces shall be allowed to remain beneath substantially improved structures provided all other standards of construction set forth in Section 16.52.130 and the following conditions are met:

  (1) The lowest floor of the living space of the existing structure is at the elevation required under subsection (c) above;

  (2) The below-grade crawl space shall be backfilled to the maximum extent possible without violating Uniform Building Code requirements for

minimum crawl space height;

  (3) The crawl space grade is not more than two feet below the lowest adjacent grade outside the foundation;

  (4) The height of the crawl space, measured from the interior grade of the crawl space to the top of the foundation wall, does not exceed four

feet;

  (5)  There is an adequate drainage system capable of removing floodwaters from the interior area of the crawl space within seventy-two hours

after the flood event; and

  (6) The expected velocity of the floodwaters at the site does not exceed five feet per second.

(e)  Prohibition of Residential Basement Construction.

  (1)  For residential structures located within a Special Flood Hazard Area:

    (A) No new basements shall be constructed; and

    (B) No existing basements shall be expanded.

(Ord. 5580 § 1, 2023: Ord. 5566 § 6, 2022: Ord. 4824 § 2, 2004: Ord. 4557 § 7, 1999: Ord. 3795 § 7 (part), 1988)

(a) 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.

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

(Ord. 3795 § 7 (part), 1988)

(a) All preliminary subdivision proposals shall identify the special flood hazard area and the elevation of the base flood.

(b) All subdivision plans will provide the elevation of proposed structure(s) and pad(s). If the site is filled above the base flood elevation, the lowest floor and final pad elevations shall be certified by a registered professional engineer or surveyor and provided to the floodplain administrator.

(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.

(e) All subdivisions shall provide adequate drainage to reduce exposure to flood hazards.

(Ord. 4557 § 8, 1999: Ord. 3795 § 7 (part), 1988)

All new and replacement manufactured homes and additions to manufactured homes on foundations in flood hazard areas or coastal high-hazard areas shall:

(a) Be elevated so that the lowest floor elevation meets requirements specified in sections16.52.130 and 16.52.180 as applicable; and

(b)  Be securely anchored to a permanent foundation system to resist flotation, collapse or lateral movement in accordance with ASCE 24.

(Ord. 5566 § 7, 2022: Ord. 3795 § 7 (part), 1988)

(a) All recreational vehicles placed onsite within Zones A, A1 - A30, AH, and AE on the Flood Insurance Rate Map will either:

(1) Be located on the site for fewer than 180 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

(2) Meet the permit requirements of Sections 16.52.110 and 16.52.120 and the elevation and anchoring for manufactured homes requirements of

Located within areas of special flood hazard established in Section16.52.060 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 shall apply:

(a) Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.

(b) If subsection (a) of this section is satisfied, all new construction and substantial improvements shall comply with all other applicable flood hazard reduction provisions of Section 16.52.130, 16.52.150, 16.52.160 and 16.52.180.

(Ord. 4557 § 10, 1999: Ord. 3795 § 7 (part), 1988)

Within coastal high hazard areas established in Section 16.52.060 the following standards shall apply:

(a)  All new construction and substantial improvements shall be elevated on adequately anchored pilings or columns and securely anchored to

such pilings or columns so that the lowest horizontal portion of the structural members of the lowest floor (excluding the pilings or columns, grade beams and bracing) is elevated to or above the base flood elevation plus 1 foot or design flood elevation, whichever is higher. Wind loading values used shall be those required by applicable state or local building standards.

(b)  All new construction and other development shall be located on the landward side of the reach of mean high tide.

(c) All new construction and substantial improvements shall have the space below the lowest floor free of obstructions or constructed with breakaway walls. Such temporarily enclosed space shall not be used for human habitation and will be usable solely for parking of vehicles, building access or storage.

(d)   Fill shall not be used for structural support of buildings.

(e) Manmade alteration of sand dunes which would increase potential flood damage is prohibited.

 (f) The floodplain administrator shall obtain and maintain the following records:

  (1)  Certification by a registered engineer or architect that a proposed structure complies with subsection (a) of this section; and

  (2) 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.

(Ord. 5566 § 8, 2022: Ord. 4557 § 11, 1999: Ord. 3795 § 7 (part), 1988)

(a) The city manager or her designee shall hear and decide appeals and requests for variances from the requirements of this chapter.

(b) The city manager shall hear and decide appeals when it is alleged there is an error in any requirement, decision, or determination made by the floodplain administrator in the enforcement or administration of this chapter.

(c) In passing upon such applications, the city manager shall consider all technical evaluations, all relevant factors, standards specified in other sections of this chapter, and:

(1) The danger that materials may be swept onto other lands to the injury of others;

(2) The danger of life and property due to flooding or erosion damage;

(3) The susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the existing individual owner and future owners of the property;

(4) The importance of the services provided by the proposed facility to the community;

(5) The necessity to the facility of a waterfront location, where applicable;

(6) The availability of alternative locations for the proposed use which are not subject to flooding or erosion damage;

(7) The compatibility of the proposed use with existing and anticipated development;

(8) The relationship of the proposed use to the Comprehensive Plan and floodplain management program for that area;

(9) The safety of access to the property in time of flood for ordinary and emergency vehicles;

(10) The expected heights, velocity, duration, rate of rise, and sediment transport of the floodwaters expected at the site; and

(11) The costs of providing governmental services during and after flood conditions, including maintenance and repair of public utilities and facilities such as sewer, gas, electrical, and water system, and streets and bridges.

(d) Upon consideration of the factors of subsection (c) of this section and the purposes of this chapter, the city manager may attach such conditions to the granting of variances as she deems necessary to further the purposes of this chapter.

(e) The floodplain administrator shall maintain the records of all appeal actions and report any variances to the Federal Insurance Administration upon request.

(Ord. 4557 § 12, 1999: Ord. 3795 § 7 (part), 1988)

(a) Variances may be issued, as follows:

(1) For new construction, substantial improvement, and other proposed new development to be erected on a lot of one-half acre or less in size contiguous to and surrounded by lots with existing structures constructed below the base flood level, provided that the procedures of Sections 16.52.110, 16.52.120, 16.52.130, 16.52.140, 16.52.150, 16.52.160, 16.52.170 and 16.52.180 of this ordinance shall be fully considered, and, as the lot size increases beyond one-half acre, the technical justifications required for issuing the variance shall increase; and

(2) For new construction and substantial improvements and for other development necessary for the conduct of a functionally dependent use provided that the provisions of subsections (a) through (c) of this section are satisfied and that the structure or other development is protected by methods that minimize flood damages during the base flood and create no additional threats to public safety.

(b) Variances shall not be issued within any designated floodway if any such increase in flood levels during the base flood discharge would result.

(c) Variances shall be issued only upon:

(1) A showing of good and sufficient cause; and

(2) A determination that:

(A) The variance is reasonably necessary, considering the flood hazard, to afford relief;

(B) The failure to grant the variance would result in exceptional hardship to the applicant; and

(C) The granting of a variance will not result in increased flood heights, additional threats to public safety, extraordinary public expense, create nuisances, cause fraud on or victimization of the public, or conflict with existing local laws or ordinances.

(d) Any applicant to whom a variance is granted shall be given written notice over the signature of a community official that:

(1) The issuance of a variance to construct a structure below the base flood elevation could result in a substantial increase in the cost of flood insurance; and

(2) Any construction below the base flood elevation could increase the risk to life and property.

(e) A copy of the notice shall be recorded by the floodplain administrator in the office of the Santa Clara county recorder and shall be recorded in a manner so that it appears in the chain of title of the affected parcel of land.

(f) The floodplain administrator will maintain a record of all variance actions, including the essential facts supporting their issuance, and the administrator shall report on the variances that are issued in the city of Palo Alto's biennial report that is submitted to the Federal Insurance Administration of the Federal Emergency Management Agency.

(Ord. 4557 § 13, 1999: Ord. 3795 § 7 (part), 1988)