13.13.040 Frequently flooded areas | Bothell Municipal Code

13.13.040 Frequently flooded areas.

A. Designation of Frequently Flooded Areas. Frequently flooded or special flood hazard areas are lands subject to a one percent or greater chance of flooding in any given year; otherwise known as the “100-year” flood or the “base” flood. These areas could include, but are not limited to, streams, lakes, wetlands and their associated floodplains, flood fringes or areas identified by the Federal Insurance Administration in a scientific and engineering report entitled “The Flood Insurance Study for King County, Washington and Incorporated Areas” dated March 30, 1998, and any revisions thereto, and “The Flood Insurance Study for Snohomish County, Washington, and Incorporated Areas,” dated November 8, 1999, and any revisions thereto, with accompanying FIRMs are hereby adopted by reference and declared to be part of this chapter. The flood insurance studies and FIRMs are on file at the office of the city clerk.

1. Frequently flooded or flood hazard areas are subject to periodic inundation which results in loss of life and property, 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. These flood losses are 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 or which are inappropriately located in the floodplain also contribute to the flood loss.

2. It is the intent of the city of Bothell, by way of this section, to reduce, minimize and/or prevent the public and private losses noted above and to promote the public health, safety and general welfare, through the regulation of development within frequently flooded areas designed to:

a. Restrict or prohibit 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. Require that uses vulnerable to floods, including facilities which serve such uses, be protected against flood damage at the time of initial construction;

c. Control and minimize the alteration of natural floodplains, stream channels and natural protective barriers which help accommodate or channel floodwaters;

d. Control filling, grading, dredging and other development which may increase flood damage; and

e. Prevent or regulate the construction of flood barriers which will unnaturally divert floodwaters or which may increase flood hazards in other areas.

1. Designation of the Local Flood Management Administrator. The public works director is the administrator. The public works director is appointed to administer and implement this section by reviewing permit applications in accordance with its provisions and providing final findings to the shoreline administrator who shall issue or deny the underlying shoreline permit based on said findings and consistency with all other provisions of the SMP.

2. Duties and Responsibilities of the Local Flood Management Administrator. Duties of the local flood management administrator shall include, but not be limited to:

(1) Review all permit applications within areas of special flood hazard to determine that the requirements of this chapter and this section have been satisfied;

(2) Review all permit applications within areas of special flood hazard to determine that all necessary permits have been obtained from those federal, state or local governmental agencies from which prior approval is required;

(3) Review all permit applications within areas of special flood hazard to determine if the proposed development is located in the floodway. If located in the floodway, assure that the encroachment provisions of subsection (G)(4)(l) of this section are met.

(1) When base flood elevation data has not been provided, the local flood management 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 fulfill the administrator’s duties and responsibilities under this chapter.

(2) Review of Building Permits. Where base flood elevation data has not been provided or is not available either through the flood insurance study or from another authoritative source, applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is the judgment of the city engineer and includes use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet above the highest adjacent grade in these zones may result in higher insurance rates.

D. Relationship to Other Critical Areas Regulations. In addition to the provisions of this section, requirements for buffers, sensitive area tracts, development setback lines, permitted alterations, mitigation and monitoring for a development proposal site on or adjacent to a flood hazard area shall be as established elsewhere in this chapter for the streams, wetlands, wildlife habitat conservation areas or other critical areas which form the constituent elements of the floodplain.

1. Where base flood data is provided through the flood insurance study or as required in subsection (C)(2)(b)(1) of this section, obtain and record the actual elevation (in relation to mean sea level) of the lowest floor (including basement) of all new or substantially improved structures, and whether or not the structure contains a basement.

2. For all new or substantially improved floodproofed structures in a special flood hazard area:

a. Verify and record the actual elevation in relation to sea level to which the structure was floodproofed.

b. Maintain the floodproofing certifications required by this section. The applicant must provide certification by a professional civil engineer or land surveyor licensed in the state of Washington of the actual as-built elevation of the lowest floor, including basement (in relation to mean sea level), and, if applicable, the actual as-built elevation to which the structure is floodproofed. If the structure has a basement, this must be indicated.

c. Maintain for public inspection all records pertaining to the provisions of this section.

F. Other Agencies. In all flood hazard areas, the city of Bothell shall honor all existing contractual obligations with any federal agency.

1. Any activities in a special flood hazard area as defined by this chapter shall require the appropriate shoreline permit and shall be subject to the requirements of this section.

a. Notify adjacent communities and the state Department of Ecology prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration.

b. Require that maintenance is provided within the altered or relocated portion of said watercourse so that the flood-carrying capacity is not diminished.

3. Interpretation of FIRM Boundaries. Make interpretations where needed, as to exact location of the boundaries of the areas of special flood hazards. The person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation as provided for elsewhere in this chapter.

4. General Standards. In all areas of special flood hazards, the following standards are required:

a. In areas where a regulatory floodway has not been designated, no new construction, substantial improvements, or other development (including fill) shall be permitted within zone AE on the community’s FIRMs, unless it is demonstrated that the cumulative effect of the proposed development when combined with all other existing development will not increase the water surface elevation of the base flood more than six inches at any point within the community.

(1) All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure;

(2) All manufactured homes must likewise be anchored to prevent flotation, collapse, or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors, or as otherwise provided in FEMA’s “Manufactured Home Installation in Flood Hazard Areas” guidebook.

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

(2) All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.

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

(1) Utilities shall be located in the 100-year floodplain only when no other physically feasible location is available.

(2) All new and replacement water supply systems, when permitted in the 100-year floodplain, shall be designed to minimize or eliminate infiltration of floodwaters into the system.

(3) Installation of new sanitary sewage systems in the 100-year floodplain shall be prohibited unless a waiver is granted by the applicable department of public health. If a waiver is granted, the system shall be designed to minimize or eliminate infiltration of floodwaters into the system and discharge from the system into floodwaters.

(4) Installation of replacement sanitary sewage systems within the 100-year floodplain shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters.

(5) On-site waste disposal systems, when permitted in the 100-year floodplain, shall be located to avoid impairment to them or contamination from them during flooding.

(6) Construction of sewage treatment facilities in the 100-year floodplain shall be prohibited.

(7) Utility transmission lines transporting hazardous substances within the 100-year floodplain shall be buried at a minimum depth of four feet below the maximum depth of scour for the base flood as predicted by a professional civil engineer licensed in the state of Washington and shall achieve sufficient negative buoyancy so that any potential for flotation or upward migration is eliminated.

e. Critical facilities shall not be constructed in the 100-year floodplain.

f. Construction of livestock manure storage facilities and associated nonpoint source water pollution facilities shall not be constructed in the 100-year floodplain.

(1) New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated one foot above base flood elevation;

(2) Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or 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) 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;

(B) The bottom of all openings shall be no higher than one foot above grade;

(C) Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwaters.

h. Nonresidential Construction. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall either have the lowest floor, including basement, elevated one foot above the level of the base flood elevation; or together with attendant utility and sanitary facilities shall:

(1) Be floodproofed so that below one foot above the base flood level the structure is watertight with walls substantially impermeable to the passage of water.

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

(3) Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the official as set forth elsewhere in this section.

(4) Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection (G)(4)(g) of this section.

(5) Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the floodproofed level.

i. Manufactured Homes. All manufactured homes to be placed or substantially improved within Zones A, AE, and X shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is one foot above the base flood elevation and be securely anchored to an adequately anchored foundation system in accordance with the provisions of subsection (G)(4)(b) of this section.

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

(2) Subdivisions, short subdivisions, and binding site plans shall follow these requirements:

(A) New building lots shall contain 5,000 square feet or more of buildable land outside the 100-year floodplain and building setback lines shall be shown on the face of the plat to restrict permanent structures to this 5,000-square-foot or greater area;

(B) All public utilities and facilities such as sewer, gas, electrical and water systems shall be located and constructed consistent with subsection (G)(4)(d) of this section;

(D) Where base flood elevation data has not been provided or is not available from another authoritative source, it shall be generated for subdivision proposals and other proposed developments which contain at least 50 lots or five acres, whichever is less;

(E) Base flood data and flood hazard notes shall be shown on the face of the recorded plat, including, but not limited to, the base flood elevation, required flood protection elevations, and the boundaries of the 100-year floodplain; and

(F) The following note shall appear on the face of the recorded plat for all affected lots:

NOTICE

Lots and structures located within flood hazard areas may be inaccessible by emergency vehicles during flood events. Residents and property owners should take appropriate advance precautions.

k. Floodways. Located within areas of special flood hazard 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 this subsection is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section.

(3) Construction or reconstruction of residential structures is prohibited within designated floodways, except for (A) repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; and (B) repairs, reconstruction or improvements to a structure, the cost of which does not exceed 50 percent of the market value of the structure either (1) before the repair, reconstruction, or improvement is started, or (2) if the structure has been damaged, and is being restored, before the damage occurred. Any project for improvement of a structure to correct existing violations of state or local health, sanitary, or safety toward specifications which have been identified by the local code official and which are the minimum necessary to assure safe living conditions or to structures identified as historic places shall not be included in the 50 percent.

l. Encroachments. The cumulative effect of any proposed development, when combined with all other existing and anticipated development, shall not increase the water surface elevation of the base flood more than six inches at any point.

m. Compensatory Storage. New development shall not reduce the effective flood storage volume of the regulatory floodplain. A development proposal shall provide compensatory storage if grading or other activity eliminates any effective flood storage volume. Compensatory storage shall:

(1) Provide equivalent volume at equivalent elevations to that being displaced. For this purpose, “equivalent elevation” means having similar relationship to ordinary high water and to the best available 10-year, 50-year and 100-year water surface profiles;

(2) Be hydraulically connected to the source of flooding; and

(3) Provide compensatory storage in the same construction season as when the displacement of flood storage volume occurs and before the flood season begins.

(4) Be graded and vegetated to allow fish access during flood events without creating fish stranding areas.

n. Recreational Vehicles. Recreational vehicles placed on sites will be required to either:

(1) Be on the site for fewer than 180 consecutive days; and

(2) Be fully licensed and ready for highway use, on its wheels or jacking system, be attached to the site only by quick disconnect type utilities and security devices and have no permanently attached additions; or

(3) Meet the requirement of subsection (G)(4)(b) of this section and the elevation and anchoring requirements for manufactured homes. (Ord. 2112 § 3 (Exh. C), 2013).