Chapter 20.49
FP FLOODPLAIN OVERLAY ZONES

Sections:

20.49.000    FP zones.

20.49.005    Description and purpose.

20.49.010    Permitted and conditionally permitted uses – FPM zone.

20.49.015    Development and performance standards – FPM zone.

20.49.030    Permitted and conditionally permitted uses – FPB zone.

20.49.035    Development and performance standards – FPB zone.

20.49.040    Floodplain waivers.

20.49.045    Warning and disclaimer of liability.

20.49.000 FP zones.

The following FP floodplain overlay zones are established. Properties so designated shall be subject to the provisions contained in this chapter:

FPM     Floodplain management overlay zone

FPB     Floodplain basin overlay zone

(Ord. 2147 Exh. A, 1987).

20.49.005 Description and purpose.

The FP floodplain management overlay zones are intended to protect lives and property improvements from flood hazards, preserve the integrity of the floodway to carry floodwaters, preserve riparian vegetation along watercourses and prevent displacement of floodwaters onto other properties. As overlay zones, they establish development regulations in addition to those prescribed by the underlying zone in which the property is located. In addition to this intent, each FP zone has its own specific and unique intent as follows:

(1) FPM Floodplain Management Overlay Zone. The FPM zone is intended to apply to those lands within the floodplain subject to inundation by a 100-year flood. It includes lands within both the floodway and floodway fringe. This area is also referred to as the “area of special flood hazard” under the provisions of Chapter 21.06 PMC.

(2) FPB Floodplain Basin Overlay Zone. The FPB zone is intended to apply to those lands subject to frequent, but shallow inundation by storm waters, including the 100-year flood. Such lands typically have poor surface drainage, but are not typically located immediately adjacent to the floodway. This area is also referred to as the “area of shallow flooding” under the provisions of Chapter 21.06 PMC. (Ord. 2147 Exh. A, 1987).

20.49.010 Permitted and conditionally permitted uses – FPM zone.

(1) Regulations governing uses in the underlying zone shall apply to properties in the FPM zone.

(2) Within an identified floodway, no buildings or structures shall be permitted except bridges, culverts, dikes and similar structures necessary to the construction or entrance of highways, roads, streets or access routes intersecting or crossing a floodway.

(3) Flood-control facilities or any construction necessary for the protection of floodways or to prevent erosion of or damage to adjoining nonfloodway lands, or any construction necessary for the conservation of channelization of floodwaters or watercourses shall be permitted in the FPM zone. (Ord. 2147 Exh. A, 1987).

20.49.015 Development and performance standards – FPM zone.

The following development and performances standards apply to properties located in the FPM zone. Determining compliance with these standards shall be the responsibility of the city engineer:

(1) Buildings, structures and manufactured homes within the FPM zone shall be constructed so that the lowest habitable floor is situated at least one foot above the adjacent predicted elevation of the surface of the floodwaters of the 100-year flood, or otherwise floodproofed to prevent inundation of said lowest habitable floor.

(2) Buildings, structures and manufactured homes within the FPM zone shall be constructed and/or installed so as to prevent flotation, collapse or lateral movement. Anchoring systems for manufactured homes and portable structures shall be capable of carrying a force of 4,800 pounds or a wind force of 90 miles per hour or greater.

(3) All new and replacement water supply and sanitary sewer systems shall be designed to prevent infiltration of floodwater. Sanitary sewers shall be further designed to ensure continuing discharge in the event of flooding. On-site sanitary effluent disposal systems are prohibited.

(4) Buildings, structures, manufactured homes, filling and/or grading conducted within an identified floodplain shall not obstruct the floodway or watercourse so as to inhibit its ability to transport floodwaters. Nor shall such improvements be permitted so as to increase floodwater depth, volume, velocity or severity to other properties. The city engineer may require, in connection with any proposal for development within the FPM zone (including but not limited to filling, grading, land division, and building construction), the submittal of technical documentation, prepared by a registered professional engineer and acceptable to the city engineer demonstrating that the proposed development will not increase floodwater depth, volume, velocity or severity to other properties. (Ord. 2147 Exh. A, 1987).

20.49.030 Permitted and conditionally permitted uses – FPB zone.

Regulations governing uses in the underlying zone shall apply to properties in the FPB zone. (Ord. 2147 Exh. A, 1987).

20.49.035 Development and performance standards – FPB zone.

The following development and performance standards shall apply to properties in the FPB zone. Determining compliance with these standards shall be the responsibility of the city engineer:

(1) Buildings, structures or manufactured homes within the FPB zone shall have the lowest habitable floor elevated above the grade of the building site. Nonresidential building sites shall be filled to an elevation of at least one foot above the elevation of the crown of the highest adjacent public street for at least 15 feet beyond the perimeter of said building or structure. Residential structures shall have the lowest floor, including the basement, elevated above the highest adjacent grade of the site. Greater depth of fill may be required if such fill is necessary to ensure positive drainage from the site to the city’s storm drainage system.

(2) Except as provided for in subsection (1) of this section, buildings, structures, manufactured homes, filling and/or grading on properties in the FPB zone shall be designed so as to prevent displacement of floodwaters or increase the severity of floodwaters to other properties. The city engineer may require, in connection with any proposal for development within the FPB zone (including but not limited to filling, grading, land division, and building construction), the submission of technical documentation, prepared by a registered professional engineer and acceptable to the city engineer demonstrating that the proposed development will not increase floodwater depth, volume, velocity or severity to other properties.

(3) Where hazardous floodwater velocities are determined to occur, appropriate floodproofing measures shall be implemented in the design of the development. (Ord. 2196 § 5, 1989; Ord. 2147 Exh. A, 1987).

20.49.040 Floodplain waivers.

The public works director is authorized to waive the provisions of this chapter provided the following criteria can be met, where applicable:

(1) The subject property is found not to be within the 100-year floodplain or flood hazard area or subject to frequent storm water inundation;

(2) The strict compliance with the regulations set forth in PMC 20.49.015 or 20.49.035 is neither necessary nor practical to assure that the description and purpose of the floodplain overlay zones, as described in PMC 20.49.005, is achieved;

(3) That strict compliance with the regulations set forth in PMC 20.49.015 or 20.49.035 would prevent reconstruction, rehabilitation, or restoration of improvements and/or property listed on the National Register of Historic Places or the Washington State Inventory of Historical Places.

In consideration of applications for floodplain waiver, the public works director shall require the submission of technical documentation, prepared by a registered engineer and acceptable to the public works director, which explains how the proposal complies with the criteria set forth in this section. The public works director shall approve, modify or deny any such application for floodplain waiver within 30 days of submission of a sufficient application. The decision of the public works director may be appealed to the board of adjustment as an interpretation review pursuant to Chapter 20.87 PMC. All actions of the public works director and board shall be made in writing and include the facts which cause such actions to comply with the applicable criteria of this section. (Ord. 2268 § 34, 1991; Ord. 2147 Exh. A, 1987).

20.49.045 Warning and disclaimer of liability.

The degree of flood protection required by this chapter is considered reasonable for regulatory purposes and is based on scientific and engineering documentation and considerations. Larger floods 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 FP zones 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 or the Federal Insurance Administration, for any flood damages that result from reliance on this chapter or any administrative decision lawfully made under this chapter. (Ord. 2147 Exh. A, 1987).