Chapter 16C.05.36
FLOODWAY USES

Sections:

16C.05.36.010    Permitted Uses.

16C.05.36.020    Prohibited Uses.

16C.05.36.010 Permitted Uses.

Permitted uses include any use permitted in the zoning district in accordance with YCC Title 19 of this code, provided that said use is in compliance with the flood hazard protection standards of Chapter 16C.05.28 and other applicable provisions of this title, and will have a negligible effect upon the floodway in accordance with the floodway encroachment provisions of Section 16C.05.36.020(2):

(1)    Surface mining, provided that the applicant can provide clear evidence that such uses will not divert flood flows causing channel-shift or erosion, accelerate or amplify the flooding of downstream flood hazard areas, increase the flooding threat to upstream flood hazard areas, or in any other way threaten public or private properties. When allowed, such removal shall comply with the provisions of Title 19 and the Yakima County Shoreline Management Master Program Regulations (Shoreline Master Program (Title 16D), where applicable);

(2)    Utility transmission lines, unless otherwise prohibited by this chapter; except that when the primary purpose of such a transmission line is to transfer bulk products or energy through a floodway en route to another destination, as opposed to serving customers within a floodway, such transmission lines shall conform to the following:

(a)    All utility transmission lines shall cross floodways by the most direct route feasible as opposed to paralleling floodways;

(b)    Electric transmission lines shall span the floodway with support towers located in flood fringe areas or beyond. Where floodway areas cannot be spanned due to excessive width, support towers shall be located to avoid high floodwater velocity and/or depth areas, and shall be adequately floodproofed;

(c)    Buried utility transmission lines transporting hazardous and nonhazardous materials, including but not limited to crude and refined petroleum products and natural gas, water and sewage, shall be buried a minimum of four feet below the maximum established scour of the waterway, as calculated on the basis of hydrologic analyses. Such burial depth shall be maintained horizontally within the hydraulic floodway to the maximum extent of potential channel migration as determined by hydrologic analyses. In the event potential channel migration extends beyond the hydraulic floodway, conditions imposed upon floodway fringe and special flood hazard areas shall also govern placement. All hydrologic analyses are subject to acceptance by Yakima County, shall assume the conditions of a one-hundred-year frequency flood as verified by the U.S. Army Corps of Engineers, and shall include on-site investigations and consideration of historical meander characteristics in addition to other pertinent facts and data. The use of riprap as a meander containment mechanism within the hydraulic floodway shall be consistent with the Yakima County Shoreline Management Master Program Regulations;

(d)    Beyond the maximum extent of potential channel migration, utility transmission lines transporting hazardous and nonhazardous materials shall be buried below existing natural and artificial drainage features. Burial depth in all agricultural areas requiring or potentially requiring subsurface drainage shall be a minimum of six feet as measured from ground surface to the top of the transmission line, or at other such depth as deemed necessary by on-site investigations performed by a qualified soils expert familiar with Yakima County soils. Burial depth in all other agricultural and nonagricultural floodway areas shall be determined on the basis of accepted engineering practice and in consideration of soil conditions and the need to avoid conflict with agricultural tillage;

(e)    Aboveground utility transmission lines, not including electric transmission lines, shall only be allowed for the transportation of nonhazardous materials where an existing or new bridge or other structure is available and capable of supporting the line. When located on existing or new bridges or other structures with elevations below the level of the one-hundred-year flood, the transmission line shall be placed on the downstream side and protected from flood debris. In such instances, site-specific conditions and flood damage potential shall dictate placement, design and protection throughout the floodway. Applicants must demonstrate that such aboveground lines will have no appreciable effect upon flood depth, velocity or passage, and shall be adequately protected from flood damage. If the transmission line is to be buried except at the waterway crossing, burial specifications shall be determined as in subsection (2)(c) of this section;

(f)    Aboveground utility transmission line appurtenant structures, including valves, pumping stations, or other control facilities, shall not be permitted in the floodway;

(g)    Where a floodway has not been determined by preliminary Corps of Engineers’ investigations or official designation, a floodway shall be defined by qualified engineering work by the applicant on the basis of a verified one-hundred-year flood event;

(3)    Construction or reconstruction of residential structures only as authorized in Section 16C.05.36.020(3);

(4)    Improvements to existing residential structures that are not substantial improvements per Section 16C.02.395; provided, the improvement complies with the requirement set forth in Section 16C.05.36.020(2);

(5)    Water-dependent utilities and other installations which by their very nature must be in the floodway. Examples of such uses are: dams for domestic/industrial water supply, flood control and/or hydroelectric production; water diversion structures and facilities for water supply, irrigation and/or fisheries enhancement; floodwater and drainage pumping plants and facilities; hydroelectric generating facilities and appurtenant structures; structures and nonstructural uses and practices; provided, that the applicant shall provide evidence that a floodway location is necessary in view of the objectives of the proposal, and provided further that the proposal is consistent with other provisions of this title and the Shoreline Management Master Program (YCC Title 16D). In all instances of locating utilities and other installations in floodway locations, project design must incorporate floodproofing and otherwise comply with subsection (2) above;

(6)    Dikes, provided that the applicant can provide evidence that:

(a)    Adverse effects upon adjacent properties will not result relative to increased floodwater depths and velocities during the base flood or other more frequent flood occurrences,

(b)    Natural drainage ways are minimally affected in that their ability to adequately drain floodwaters after a flooding event is not impaired,

(c)    The proposal has been coordinated through the appropriate diking district where applicable, and that potential adverse effects upon other affected diking districts have been documented;

(7)    Roads and bridges, subject to the regulations of subsection (2) above.

(Ord. 5-2017 § 2(C) (Exh. 1) (part), 2017: Res. 80-2016 (Exh. A) (part), 2016; Ord. 13-2007 §1 (Exh. A)(16C.05.36.010), 2007).

16C.05.36.020 Prohibited Uses.

The following uses/developments are prohibited in the floodway:

(1)    Any structure, including manufactured homes, designed for, or to be used for human habitation of a permanent nature;

(2)    All encroachments, including fill, new construction and other development unless certification by a registered professional engineer is provided demonstrating through hydrologic and hydraulic analysis performed in accordance with standard engineering practice that the effect of the subject encroachment together with the cumulative effects of all similar potential encroachments shall not materially cause water to be diverted from the established floodway, cause erosion, obstruct the natural flow of water, reduce the carrying capacity of the floodway, or result in any increase in flood levels during the occurrence of the base flood discharge;

(3)    Construction or reconstruction of residential structures 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 fifty percent of the assessed value of the structure either (i) before the repair, reconstruction or improvement is started, or (ii) if the structure has been damaged and is being restored, before the damage occurred. Work done on structures to correct existing violations of existing health, sanitary or safety codes, or to structures identified as historic places shall not be included in the fifty percent. If subsection (2) of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of Chapters 16C.05.20 through 16C.05.72, including those set forth in subsection (5) below;

(4)    The construction or storage of any object subject to flotation or movement during flood level periods;

(5)    The following uses, due to their high degree of incompatibility with the purpose of establishing and maintaining a functional floodway, are specifically prohibited:

(a)    The filling of wetlands, except as authorized under Chapter 16C.06 (Fish and Wildlife Habitat and the Stream Corridor System) and Chapter 16C.07 (Wetlands) of this title;

(b)    Solid waste landfills, dumps, junkyards, outdoor storage of vehicles and/or materials;

(c)    Damming or relocation of any watercourse that will result in any downstream increase in flood levels during the occurrence of the base flood discharge;

(6)    The listing of prohibited uses in this section shall not be construed to alter the general rule of statutory construction that any use not permitted is prohibited.

(Ord. 5-2017 § 2(C) (Exh. 1) (part), 2017: Ord. 13-2007 §1 (Exh. A)(16C.05.36.020), 2007).