Chapter 21.10 FLOODPLAIN MANAGEMENT

RCW 35A.63.100 authorizes the Walla Walla city council, by ordinance or other action to the extent the Walla Walla city council deems necessary or appropriate, to implement or give effect to the comprehensive plan or parts thereof in developing the city of Walla Walla and in regulating the use of land. (Ord. 2015-12 § 2 (part), 2015).

21.10.020 Findings.

A. The flood hazard areas of Walla Walla County are subject to periodic inundation which may cause 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.

B. These flood losses are caused by past development practices, 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 flood proofed, elevated or otherwise protected from flood damage also contribute to the flood loss. (Ord. 2015-12 § 2 (part), 2015).

21.10.030 Purpose.

It is the purpose of this chapter to promote the 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 expenditure of public money and costly flood control 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 flood blight areas;

G. To insure that potential buyers are notified that property is in an area of special flood hazard; and

H. To insure that those who develop and occupy the areas of special flood hazard assume responsibility for their actions. (Ord. 2015-12 § 2 (part), 2015).

21.10.040 Methods and general provisions.

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 increase flood hazards in other areas. (Ord. 2015-12 § 2 (part), 2015).

21.10.050 Definitions.

Unless specifically defined in this section, words or phrases used in this chapter shall be interpreted so as to give them the meaning they have in common usage and to give this chapter its most reasonable application:

“Administrator” (known and referred to alternatively herein as the “development services director,” “development services manager,” “director,” or “zoning administrator”) means the director of the development services department or such other person to whom the city manager assigns the primary responsibility of administering and enforcing this code, and such other staff granted authority to act on behalf of director.

“Appeal” means a request for a review of the administrator’s interpretation of any provision of this chapter or a request for a variance.

“Area of shallow flooding” means a designated AO or AH zone on the flood insurance rate map (FIRM). 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. AO is characterized as sheet flow and AH indicates ponding.

“Base flood” means the flood having one percent chance of being equaled or exceeded in any given year.

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

“Development” for the purposes of administering this code means any manmade 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 the storage of equipment or materials, located within the area of special flood hazard.

“Elevated building” means, for insurance purposes, a nonbasement building that has its lowest elevated floor raised above ground level by foundation walls, shear walls, post, piers, pilings, or columns.

“Existing manufactured home park or subdivision” means a manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including, at a minimum, the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) is completed before the effective date of the adopted floodplain management regulations.

“Expansion to an existing manufactured home park or subdivision” means the preparation of additional sites by the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads).

“Flood” or “flooding” means a general and temporary condition of partial or complete inundation of normally dry land areas from the unusual and rapid accumulation of runoff of surface waters from any source.

“Flood insurance rate map (FIRM)” means the official map on which the Federal Insurance Administration has delineated both the areas of special flood hazards and the risk premium zones applicable to the community.

“Flood insurance study (FIS)” means the official report provided by the Federal Insurance Administration that includes flood profiles, the Flood Insurance Rate Maps, and the water surface elevation of the base flood.

“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.

“Lowest floor” means the lowest floor of the lowest enclosed area (including basement). An unfinished or flood resistant enclosure, usable solely for 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 such enclosure is not built so as to render that structure in violation of the applicable nonelevation design requirements of this code.

“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 connected to the required utilities. For floodplain management purposes “manufactured home” also includes park trailers, travel-trailers and other similar vehicles placed on a site for greater than one hundred eighty consecutive days. For insurance purposes, “manufactured home” does not include park trailers, travel trailers and other similar vehicles.

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

“New construction” means structures for which the “start of construction” commenced on or after the effective date of the ordinance codified in this chapter.

“New manufactured home park or subdivision” means a manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including, at a minimum, the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) is completed on or after the effective date of adopted floodplain management regulations.

“Obstruction” means any dam, wall, wharf, embankment, levee, dike, pile, abutment, projection, excavation, channel rectification, bridge conduit, culvert, building, wire, fence, rock travel, refuse, fill, structure or matter in, along, across, or projecting into any channel, watercourse, or regulatory flood hazard area which may impede, retard or change the direction of flow of water, either in itself or by catching or collecting debris carried by such water, or that is placed where the flow of water might carry the same downstream to damage of life or property.

“Recreational vehicle” means a vehicle (1) built on a single chassis; (2) four hundred square feet or less when measured at the largest horizontal projection; (3) designed to be self-propelled or permanently towable by a light duty truck; and (4) designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, camping, travel, or seasonal use.

“Special flood hazard area” means the land in the floodplain within a community subject to a one percent or greater chance of flooding in any given year.

“Start of construction” includes substantial improvement, and means the date the building permit was issued, provided the actual start of construction, repair, reconstruction, placement or other improvement was within one hundred eighty days of the permit date. 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. For a substantial improvement, the actual start of construction means the first alteration of any wall, ceiling, floor, or other structural part of a building, whether or not that alteration affects the external dimensions of the building.

“Structure” means a walled and roofed building, including a gas or liquid storage tank that is principally above ground. Manufactured homes are considered structures.

“Substantial damage” means damage of any origin sustained by a structure whereby the cost of restoring the structure to its before damaged condition would equal or exceed fifty percent of the market value of the structure before the damage occurred.

“Substantial improvement” means any repair, reconstruction or improvement of a structure, the cost of which equals or exceeds fifty percent of the market value of the structure either:

1. Before the improvement or repair is started; or

2. If the structure has been damaged and is being restored, before the damage occurred. For the purposes of this definition “substantial improvement” is considered to occur when the first alteration of any wall, ceiling, floor, or other structural part of the building commences, whether or not that alteration affects the external dimensions of the structure.

The term does not, however, include either:

1. Any project for improvement of a structure to comply with existing state or local health, sanitary, or safety code specifications which have been previously identified by the local code enforcement official and which are solely necessary to assure safe living conditions; or

2. Any alteration of a structure listed on the National Register of Historic Places or a State Inventory of Historic Places.

“Water-dependent” means a structure for commerce or industry that cannot exist in any other location and is dependent on the water by reason of the intrinsic nature of its operations. (Ord. 2015-12 § 2 (part), 2015).

21.10.060 Applicability.

This chapter shall apply to all areas of special flood hazards within the incorporated areas of the city of Walla Walla, Washington. (Ord. 2015-12 § 2 (part), 2015).

21.10.070 Special flood hazard area – Established.

The areas of special flood hazard, as may be annexed to the city of Walla Walla, identified by the Federal Insurance Administration in a scientific and engineering report entitled, “The Flood Insurance Study for the Unincorporated Areas in Walla Walla County,” dated January 18, 2002, or as amended, with accompanying flood insurance rate maps (FIRM) is adopted by reference and declared to be a part of this chapter. The flood insurance study and FIRM are on file at the development services department. (Ord. 2015-12 § 2 (part), 2015).

21.10.080 Compliance.

No structure or land which lies within the special flood hazard area shall be constructed, located, extended, converted or subdivided or altered without full compliance with the terms of this chapter and other applicable regulations. (Ord. 2015-12 § 2 (part), 2015).

21.10.090 Greater restrictions which apply.

The floodplain management rules herein are imposed in addition to those of the underlying district. Where standards conflict, whichever imposes the more stringent restrictions shall prevail. (Ord. 2015-12 § 2 (part), 2015).

21.10.100 Interpretations.

In the interpretation and application of this chapter per Section 20.02.090, 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 state statutes. (Ord. 2015-12 § 2 (part), 2015).

21.10.110 Liability disclaimer.

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 be increased by manmade or natural causes. This chapter shall not create liability on the part of the city of Walla Walla, 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. 2015-12 § 2 (part), 2015).

21.10.120 Development authorization.

A. A development permit shall be obtained before grading, utility work, construction, plat alteration, land division or other development begins within any area of special flood hazard established herein.

B. The permit shall be for all structures including manufactured homes, as set forth in the definitions, and for all other developments including fill and other activities, also set forth in the definitions.

C. Application for a development permit shall be made on forms furnished by the administrator and may include, but not be limited to: plans in digital format acceptable to the city 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. Specifically, the following information is required in addition to that otherwise specified in Chapter 20.46:

1. Elevation in relation to mean sea level, of the lowest floor (including basement) of all structures verified by a Washington State licensed surveyor;

2. Elevation in relation to mean sea level to which any structure has been flood proofed verified by a Washington State licensed surveyor;

3. Certification by a Washington State licensed professional engineer or architect that the flood proofing methods for any nonresidential structure meet the flood proofing criteria provided herein, and the International Building Code as may be amended and adopted by the city;

4. Description of the extent to which any watercourse will be altered or relocated as result of proposed development. (Ord. 2015-12 § 2 (part), 2015).

21.10.130 Administrator designated.

The administrator as defined herein is appointed to administer and implement this chapter by granting or denying development permit applications in accordance with its provisions. (Ord. 2015-12 § 2 (part), 2015).

21.10.140 Administrator duties.

Duties shall include, but not be limited to, the following:

A. Permit Review.

1. Review all development permits to determine that all necessary permits have been obtained from those federal, state or local governmental agencies from which prior approval is required.

2. Review all development permits to determine if the proposed development is located in the floodway. If located in the floodway assure that the provisions of Section 21.10.260 are met.

B. Use of Other Base Flood Data. When base flood elevation data has not been provided (in A and V zones) in accordance of the provisions of this title, the director 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 this title.

C. Information to Be Obtained and Maintained.

1. Where base flood elevation data is provided through the flood insurance study, FIRM, or required as in subsection B of this section, obtain and record the actual (as-built) 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 flood proofed nonresidential structures where base flood elevation data is provided through the FIS, FIRM, or as required by this title:

a. Obtain and record the elevation (in relation to mean sea level) to which the structure was flood proofed.

b. Maintain the flood proofing certifications required in Section 21.10.120(C)(3).

3. Maintain for public inspection all records pertaining to the provisions of this chapter.

D. Alteration of Watercourses.

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

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

E. Interpretation of FIRM Boundaries. Make interpretations where needed, as to exact location of the boundaries of the areas of special flood hazards (for example, where there appears to be a conflict between a mapped boundary and actual field conditions). The person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation as provided in Section 21.10.100. (Ord. 2015-12 § 2 (part), 2015).

21.10.150 Flood protection standards – General.

The following standards in Sections 21.10.160 through 21.10.280 are required in all areas of special flood hazards. (Ord. 2015-12 § 2 (part), 2015).

21.10.160 Anchoring.

All anchoring shall be as prescribed by the International Building Code as amended and adopted by the city.

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

B. All manufactured homes shall be anchored to resist flotation, collapse or lateral movement by providing over-the-top and frame ties to ground anchors, and shall be installed using methods and practices that minimize flood damage. (Ord. 2015-12 § 2 (part), 2015).

21.10.170 Construction materials.

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

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

C. Electrical, heating, ventilation, plumbing and/or 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. (Ord. 2015-12 § 2 (part), 2015).

21.10.180 Utilities.

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

B. Water wells shall be located on high ground that is not in the floodway in accordance with WAC 173-160-171;

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

D. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding. (Ord. 2015-12 § 2 (part), 2015).

21.10.190 Subdivision.

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

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

C. All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage.

D. Base flood elevation data shall be provided for subdivision proposals and other proposed development which contain at least fifty lots or five acres (whichever is less). (Ord. 2015-12 § 2 (part), 2015).

21.10.200 Building permit review.

Where base flood elevation data is not available either through the flood insurance study, FIRM, 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 a local judgment and includes use of historical data, high water marks, photographs of past flooding, or similar information where available. Necessary information to make the local judgment will need to be provided by the applicant at the discretion of the administrator such as a Washington State licensed surveyor providing an elevation certificate. (Ord. 2015-12 § 2 (part), 2015).

21.10.210 Residential construction.

A. New construction and substantial improvement of any residential structure or accessory structure shall have the lowest floor, including basement, elevated to or above one foot above base flood elevation.

B. 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 Washington State licensed professional engineer or architect or must meet or exceed the following minimum criteria:

1. A minimum of two openings have a total area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided.

2. The bottom of all openings shall be no higher than one foot above grade.

3. Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwaters. (Ord. 2015-12 § 2 (part), 2015).

21.10.220 Nonresidential construction.

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

A. Be flood proofed so that below one foot or more above the base flood level the structure is watertight with walls substantially impermeable to the passage of water;

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

C. Be certified by a Washington State licensed professional engineer or architect that the standards of this section are satisfied. Such certifications shall accompany the application.

D. Nonresidential structures that are elevated, not flood proofed, must meet the same standards for space below the lowest floor as described in Section 21.10.210. (Ord. 2015-12 § 2 (part), 2015).

21.10.230 Recreational vehicles.

A. Recreational vehicles occupancy and use limitations shall be as provided in Section 20.180.090.

B. Recreational vehicles placed on sites are required to either:

1. Be fully licensed and ready for highway use, on wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, have no permanently attached additions, and be on the site for fewer than 180 consecutive days; or

2. Meet the requirements of Section 21.10.240 and the elevation and anchoring requirements for manufactured homes. (Ord. 2015-12 § 2 (part), 2015).

21.10.240 Manufactured homes.

All manufactured homes to be placed or substantially improved on sites shall:

A. Be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated one foot or more above the base flood elevation;

B. Be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement; and

C. Be placed and installed in compliance with the International Building Code and other applicable chapters of the Walla Walla Municipal Code. (Ord. 2015-12 § 2 (part), 2015).

21.10.250 AE and A1-30 zones with base flood elevations but no floodways.

In areas with base flood elevations (but a regulatory floodway has not been designated), no new construction, substantial improvements, or other development (including fill) shall be permitted within zones A1-30 and AE on the community’s FIRM, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation (compensatory flood storage analysis) of the base flood more than one foot at any point within the community. (Ord. 2015-12 § 2 (part), 2015).

21.10.260 Floodways.

Located within areas of special flood hazard established in this code 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 increase erosion potential, the following provisions apply:

A. Prohibit encroachments, including fill, new construction, substantial improvements, and other development within the floodway unless certification by a registered professional engineer is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels during the occurrence of the base flood discharge.

B. Construction or reconstruction of residential structures is prohibited within designated floodways, except for:

1. Repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; and

2. Repairs, reconstruction or improvements to a structure, the cost of which does not exceed fifty percent of the market value of the structure either (a) before the repair, or reconstruction is started, or (b) 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 code specifications which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions, or to structures identified as historic places, may be excluded in the fifty percent.

C. If subsection A of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of Sections 21.10.150 to 21.10.280.

D. Water-dependent utilities and other installations which by their very nature must be in the floodway (such as, but not limited to, bridges, flood control works, revetments, retaining walls, drainage structures, or other structures necessary to promote the public’s health, safety, and welfare) can be permitted; provided, that the applicant shall provide evidence that a floodway location is necessary, that it will not cause an adverse impact to adjacent, cross-channel or downstream properties, and that the proposal is consistent with other provisions of this title.

E. Traditional agricultural use or recreational facilities that do not require the installation of utilities or structures can be permitted; provided, that said use is in compliance with the flood hazard protection standards of Sections 21.10.150 to 21.10.280, and relevant local, state and federal regulations. (Ord. 2015-12 § 2 (part), 2015).

21.10.270 Shallow flooding areas.

Shallow flooding areas appear on FIRMs as AO zones with depth designations. The base flood depths in these zones range from one to three feet above ground where a clearly defined channel does not exist, or where the path of flooding is unpredictable and where velocity flow may be evident. Such flooding is usually characterized as sheet flow. In these areas, the following provisions apply:

A. New construction and substantial improvements of residential structures and manufactured homes within AO zones shall have the lowest floor (including basement) elevated above the highest adjacent grade to the structure, one foot or more above the depth number specified in feet on the community’s FIRM or at least two feet above the highest adjacent grade to the structure if no depth number is specified. An elevation certificate, prepared by a Washington State licensed surveyor, is required to be submitted and then verified in the field once the structure is constructed.

B. New construction and substantial improvements of nonresidential structures within AO zones shall either:

1. Have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, one foot or more above the depth number specified on the FIRM, or at least two feet if no depth number is specified, recorded on an FEMA elevation certificate; or

2. Together with attendant utility and sanitary facilities, be completely flood proofed to or above that level so that any space below that level is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. If this method is used, compliance shall be certified by a Washington State licensed professional engineer or architect.

C. Require adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures. (Ord. 2015-12 § 2 (part), 2015).

21.10.280 Appeal.

Decisions by the administrator to grant or deny issuance of a development authorization subject to this chapter may be appealed to the hearing examiner in accordance with Chapter 20.38, Closed Record Decisions and Appeals. (Ord. 2015-12 § 2 (part), 2015).