Chapter 18.38
FP FLOODPLAIN OVERLAY
Sections:
18.38.010 Purpose.
18.38.020 Areas of special flood hazard.
18.38.030 Districts established.
18.38.040 Use of other base flood data.
18.38.050 Floodway subdistrict – Permitted uses.
18.38.055 One-hundred-year floodplain subdistrict – Permitted uses.
18.38.060 Five-hundred-year floodplain subdistrict.
18.38.070 Standards – Generally.
18.38.080 Standards – Fill.
18.38.090 Standards – Structures.
18.38.100 Standards – Utilities.
18.38.110 Repealed.
18.38.120 Standards – Storage of materials and equipment.
18.38.130 Standards – Additional.
18.38.010 Purpose.
It is the purpose of the floodplain (FP) overlay zone district to promote the public health, safety and general welfare, and to minimize flood losses by provisions designed to:
A. Restrict or prohibit uses which are dangerous to human health, safety or property in times of flood, or cause increased flood heights or velocities;
B. Require that uses vulnerable to floods, including public facilities which serve such uses, be provided with flood protection at the time of initial construction;
C. Alert individuals as much as possible of lands which are unsuited for intended purposes because of flood hazard; and
D. Encourage conservation of lands prone to flooding for their recreational, agricultural, educational and wildlife values, and to protect those lands from damage due to soil erosion.
(Ord. O95-035, Amended, 12/19/1995; Ord. 883, Added, 05/06/1984)
18.38.020 Areas of special flood hazard.
The areas of special flood hazard are identified by the Federal Emergency Management, Federal Insurance Administration, in a scientific and engineering report dated April 3, 1984, and entitled, “The Flood Insurance Study for the City of Tumwater.” The Flood Insurance Study and the Flood Insurance Rate Map are on file at Tumwater City Hall, 555 Israel Road SW, Tumwater, WA 98501.
(Ord. O2007-004, Amended, 09/04/2007; Ord. O95-035, Amended, 12/19/1995; Ord. 883, Added, 05/06/1984)
18.38.030 Districts established.
The floodplain district shall apply to all areas of the city and urban growth area which are subject to flooding, as defined on the most recent edition of the Federal Emergency Management Agency Flood Insurance Rate Map and Flood Boundary and Floodway Map and shall be indicated on the zoning map. This district is further divided into three subdistricts called the floodway, the one-hundred-year floodplain, and the five-hundred-year floodplain. Each of these subdistricts are described in this chapter as to their definition and function. These subdistricts are overlay districts that shall always apply in addition to another zoning district. Where regulations conflict, the more stringent shall apply.
(Ord. O2000-024, Amended, 02/06/2001; Ord. O2000-004, Amended, 07/18/2000; Ord. O95-035, Amended, 12/19/1995; Ord. 883, Added, 05/06/1984)
18.38.040 Use of other base flood data.
When base flood elevation data has not been provided in accordance with TMC 18.38.030, any base flood elevation and floodway data available from a federal, state or other source shall be obtained and utilized in order to apply the floodplain zoning district and administer the requirements related to flood hazard and floodway areas.
(Ord. O95-035, Amended, 12/19/1995; Ord. 1199, Amended, 07/18/1989; Ord. 883, Added, 05/06/1984)
18.38.050 Floodway subdistrict – Permitted uses.
A. The following open space uses shall be permitted, subject to the requirements of the zoning district in which the land is located; and provided, that no storage of materials or equipment or other development or substantial improvement, including structures, fill and support facilities, shall be allowed:
1. Agricultural uses, such as general farming, pasture, grazing, outdoor plant nurseries, horticulture, forestry, sod farming, and wild crops harvesting; and
2. Private and public recreational uses such as picnic grounds, wildlife and nature preserves, fishing areas, biking and horseback riding trails, and golf course greenways.
B. The following uses shall be permitted, provided the requirements listed in subsection A of this section shall not apply:
1. Utility support facilities as defined in TMC 18.04.637 and fish hatchery appurtenances in accordance with all applicable local, state, or federal regulations and the following requirements:
a. Any permitted structure shall be constructed and placed on the building site so as to offer the minimum obstruction to the flow of floodwater.
b. Whenever possible, structures shall be constructed with the longitudinal axis parallel to the direction of flood flow.
c. So far as practicable, structures shall be placed approximately on the same flood flow lines as those of adjoining structures.
d. All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure.
e. Any new construction in floodways shall not cause any measurable rise in base flood elevation.
f. All new and replacement water supply systems shall be floodproofed and designed to eliminate infiltration of floodwaters into the system.
g. New and replacement sanitary sewer systems shall be floodproofed and designed to eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters.
h. Floodproofing and sealing measures must be taken to ensure that toxic or hazardous substances are not displaced or released into the floodwaters.
i. Such facilities shall not be allowed unless it can be demonstrated that there are no other practicable alternatives.
j. To the extent possible, the aboveground impact of these types of facilities and appurtenances, especially when placed in open space areas, shall be minimized as to height and mass.
2. Protection, rehabilitation, restoration and reconstruction of existing sites, buildings, structures and objects significant in American and Washington prehistory, history, architecture, archaeology or culture.
(Ord. O2007-004, Amended, 09/04/2007; Ord. O2000-024, Amended, 02/06/2001; Ord. O2000-017, Amended, 09/19/2000; Ord. O95-035, Amended, 12/19/1995; Ord. 883, Added, 05/06/1984)
18.38.055 One-hundred-year floodplain subdistrict – Permitted uses.
The following uses shall be permitted, subject to the requirements of the zoning district in which the land is located:
A. Agricultural and aquacultural uses, such as general farming, pasture, grazing, outdoor plant nurseries, horticulture, fish hatcheries and related appurtenances and interpretive centers, forestry, sod farming, and wild crop harvesting.
B. Private and public recreational uses such as parks, picnic grounds, wildlife and nature preserves, fishing areas, biking and horseback riding trails, and golf course greenways and appurtenances.
C. Support facilities in accordance with all applicable local, state, or federal regulations and the requirements listed in TMC 18.38.050(B)(1)(a) through (i).
D. Protection, rehabilitation, restoration and reconstruction of existing sites, buildings, structures and objects significant in American and Washington prehistory, history, architecture, archaeology or culture.
E. In accordance with 44 C.F.R. 60.3, recreational vehicles placed on sites within the one-hundred-year floodplain shall be on the site for fewer than one hundred eighty consecutive days or be 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.
(Ord. O2007-004, Amended, 09/04/2007; Ord. O2000-024, Added, 02/06/2001)
18.38.060 Five-hundred-year floodplain subdistrict.
A. Permitted Uses. Permitted uses in the five-hundred-year floodplain subdistrict are all uses permitted in the underlying zoning district, provided all structures are elevated at least two feet above the base flood elevation unless otherwise specified hereinafter.
B. Development Proposals. All development proposals submitted pursuant to any local ordinance or state or federal statute shall be examined to determine whether all building sites proposed will be reasonably safe from flooding. The city shall require the following:
1. That as a part of any subdivision creating five or more lots, or any development comprising five or more acres, that base flood elevation data be an essential element of application, and
2. That all such proposals be consistent with the need to minimize flood damage.
C. Structures.
1. All new construction and substantial improvements to existing residential structures shall have the lowest floor (including basement) elevated at least two feet above the base flood elevation. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, unless they are 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 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 or exit of floodwaters.
2. All new construction and substantial improvements to nonresidential construction shall:
a. Have the lowest floor (including basement) elevated at least two feet above the base flood elevation; or
b. Together with attendant utility and sanitary facilities, be completely floodproofed to at 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 the effects of buoyancy. Designs and methods for meeting this requirement must be certified by a registered professional engineer or architect;
c. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection (C)(1) of this section.
(Ord. O2007-004, Amended, 09/04/2007; Ord. O2000-024, Amended, 02/06/2001; Ord. O95-035, Amended, 12/19/1995; Ord. 1199, Amended, 07/18/1989; Ord. 1157, Amended, 06/21/1988; Ord. 883, Added, 05/06/1984)
18.38.070 Standards – Generally.
The standards set out in TMC 18.38.080 through 18.38.130 shall apply in the five-hundred-year floodplain subdistrict.
(Ord. O2000-024, Amended, 02/06/2001; Ord. O95-035, Amended, 12/19/1995; Ord. 883, Added, 05/06/1984)
18.38.080 Standards – Fill.
A. Any fill or materials proposed to be deposited must be shown to have a beneficial purpose and the amount thereof not greater than is necessary to achieve that purpose, as demonstrated by a plan submitted by the owner showing the uses to which the filled land will be put and the final dimensions of the proposed fill or other materials.
B. Such fill or other materials shall be protected against erosions by rip rap, vegetative cover, or bulk heading.
C. Structures may be allowed to be constructed on fill if the first floor or basement floor is two feet above the base flood elevation. The fill shall be no lower than two feet above the base flood elevation at least fifteen feet beyond the limits of any structure or building erected thereon.
D. No fill may be allowed which, acting above or in concert with other conditions, may increase flood hazards to other property.
(Ord. O95-035, Amended, 12/19/1995; Ord. 1157, Amended, 06/21/1988; Ord. 883, Added, 05/06/1984)
18.38.090 Standards – Structures.
A. Structures shall not be constructed for human habitation unless they can be designed as to have the habitable portion of the structure above the designated base flood elevation and the foundation constructed in such a manner as to withstand such inundation.
B. Any permitted structure shall be constructed and placed on the building site so as to offer the minimum obstruction to the flow of floodwater.
1. Whenever possible, structures shall be constructed with the longitudinal axis parallel to the direction of flood flow.
2. So far as practicable, structures shall be placed approximately on the same flood flow lines as those of adjoining structures.
C. All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure.
(Ord. O95-035, Amended, 12/19/1995; Ord. 883, Added, 05/06/1984)
18.38.100 Standards – Utilities.
A. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system.
B. New and replacement sanitary sewer systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters.
C. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
D. Construction of new support facilities may be allowed within the five-hundred-year floodplain subdistrict if no alternative site is available. Any facilities constructed within the five-hundred-year floodplain subdistrict shall have the lowest floor elevated a minimum of two feet above the level of the base flood elevation of the site. Additionally, floodproofing and sealing measures must be taken to ensure that toxic or hazardous substances are not displaced or released into the floodwaters. To the extent possible, access routes shall be elevated to or above the level of the base floodplain.
(Ord. O2000-024, Amended, 02/06/2001; Ord. O95-035, Amended, 12/19/1995; Ord. 1199, Amended, 07/18/1989; Ord. 883, Added, 05/06/1984)
18.38.110 Repealed.
(Ord. O2005-011, Amended, 07/05/2005; Ord. O2000-024, Amended, 02/06/2001; Ord. O95-035, Amended, 12/19/1995; Ord. 1199, Amended, 07/18/1989; Ord. 1157, Amended, 06/21/1988; Ord. 883, Added, 05/06/1984)
18.38.120 Standards – Storage of materials and equipment.
A. Storage or processing of materials that are buoyant, flammable, explosive or could be injurious to human, animal or plant life in time of flooding, is prohibited.
B. Storage of other materials or equipment may be allowed if not subject to major damage by floods and if firmly anchored to prevent flotation, or shall be readily removed from the area within the limited time available after flood warning.
(Ord. O95-035, Amended, 12/19/1995; Ord. 883, Added, 05/06/1984)
18.38.130 Standards – Additional.
The floodproofing standards contained in the U.S. Army Corps of Engineers publication entitled “Flood-Proofing Regulations,” EP 1165-2-314, dated June 1972, shall be employed within the floodplain overlay district where floodproofing is required.
(Ord. O2000-024, Amended, 02/06/2001; Ord. O95-035, Amended, 12/19/1995; Ord. 883, Added, 05/06/1984)