Ordinance 2909-06 - Laserfiche WebLink

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 and remains even in the absence of such flow. Sod -lined or other heavily vegetated swales and wetted 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 irrigation canals, are not considered streams unless they are 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 are also subject to the wetland regulations of this chapter. (This section shall be codified as EMC 19.37.160.) Section 17: Standard stream 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 top of the bank or ordinary high-water mark shall be determined so as to include the entire stream feature. 2. The standard buffer widths required by this chapter presume the existence of a relatively intact native vegetated community including native tree cover, shrub 39