Ordinance 3676-19 - Laserfiche WebLink

4. Type Ns Stream.Those stream segments within the ordinary high water mark, including the periodically inundated areas of their associated wetlands, that are not Type 5,Type F, or Type Np streams.These include seasonal streams in which surface flow is not present for at least some portion of a year of normal rainfall that are not located downstream from any Type Np stream segment. B. Lakes. Silver Lake shall be protected as required by the shoreline master program.All other lakes shall be subject to the regulations in this chapter. B. Definitions. For the purposes of this chapter: 1. "Channel gradient" refers to a measurement over a representative section of at least five hundred stream channel, but excluding unusually wide areas of negligible gradient such as marshy or swampy areas, beaver ponds, and impoundments. Channel gradient may be determined utilizing stream profiles plotted from United States Geological Survey topographic maps (see Washington Forest Practices Board Manual, Section 23) or a more detailed survey specific to the project site and/or area. 2. "Intermittent" refers to those stream segments that normally go dry during a portion of a year of normal rainfall or greater. 3. "Normal rainfall" refers to rainfall that is at or above the mean of the accumulated rainfall record, based upon the water year,for the city as recorded at the Seattle Tacoma International Airport,or other local rainfall recording station recognized by the city. 4. "Perennial stream" refers to those stream segments that do not go dry at any time during a year of normal rainfall. 5. "Riparian corridor" means a perennial, intermittent, ephemeral stream or swale including its channel bottom, lower and upper banks,and area beyond the top of the upper bank which influences the stream through shading and organic matter input, and is influenced by the presence of water, particularly in regard to plant composition.The riparian corridor is the transitional area between aquatic and upland ecosystems and does not necessarily include the entire floodplain of a stream. 6. "Stream" refers to those areas, excluding erosion caused by the inappropriate discharge or rerouting of storm or surface water,where surface waters flow with sufficient volume,velocity, duration, and/or frequency to scour away leaf litter and other vegetative matter and/or scour away or prevent the growth of vegetation such that clear evidence of the passage of flow is present on the land areas, which remain lined with leaf litter or other vegetative matter, do not meet the criteria of a stream. Excavated or other artificial watercourses, including swales, roadside ditches, and irri.ation canals, arc not considered streams unless they arc used to convey water which flowed in a naturally defined channel prior to the creation of the artificial watercourse or are used by salmonid fish. C. Periodically inundated wetlands that fall within the stream classifications arc also subject to the wetland regulations of this chapter. Section 20.Section 17 of Ordinance 2909-06, as amended, (Zoning Code, Critical Areas, EMC 19.37.170), is hereby amended as follows: 19.37.170 Standard stream and lake buffer requirements. A. Standard Buffer Width. It is the goal of this chapter to preserve streams and their buffers in a natural condition to the maximum extent possible. 1. Buffers shall be measured from the top of the upper bank or, if that cannot be determined, from the ordinary high water mark as surveyed in the field. In braided channels and alluvial fans, the EMC Title 19.37 (Critical Areas) Page 45