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 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 understory and ground cover. If the existing buffer is unvegetated, sparsely vegetated, or vegetated with invasive species, the buffer width shall be increased as required by this section.
3. Except as otherwise provided by EMC 19.37.050, the following minimum buffers of native vegetation shall apply to streams based upon stream classification:
|
Stream Classification (Type) |
Standard Buffer: Intact Native Vegetation |
Standard Buffer: Unvegetated; Sparsely Vegetated; or Vegetated with Invasive Species |
|---|---|---|
|
Type S |
100 feet |
150 feet |
|
Type F |
100 feet |
150 feet |
|
Type Np |
50 feet |
75 feet |
|
Type Ns |
50 feet |
75 feet |
B. Standard Buffer Width Increase. The city shall require increased buffer widths as necessary to protect streams when the stream is particularly sensitive to disturbance, or the development poses unusual impacts and the increased buffer width is necessary to protect the critical areas described in this subsection. Circumstances which may require buffers beyond minimum requirements include, but are not limited to, the following:
1. When the minimum buffer for a stream extends into an area with a slope of greater than twenty-five percent, the buffer shall be the greater of:
b. Twenty-five feet beyond the point where the slope becomes twenty-five percent or less;
2. The stream reach affected by the development proposal serves as critical fish habitat for spawning or rearing as determined by the city using information from resource agencies including, but not limited to, the Washington State Department of Fish and Wildlife, U.S. Fish and Wildlife Service, and recognized tribal nations;
3. The stream or adjacent riparian corridor is used by species listed by the federal government or the state as endangered, threatened, rare, sensitive, or monitored, or provides critical or outstanding actual or potential habitat for those species, or has unusual nesting or resting sites such as heron rookeries or raptor nesting or lookout trees;
4. The land adjacent to the stream and its associated buffer is classified as a geologically hazardous or unstable area;
5. Increased buffer width is necessary to effectively include the riparian corridor of the stream.
C. Standard Stream Buffer Width Reduction with Enhancement. The planning director may, using the review process as described in EMC Title 15, Local Project Review Procedures, reduce the standard stream buffer width only when there has previously been substantial legal alteration of the stream and/or buffer on the subject lot or adjoining lots resulting in the existing buffer being unvegetated, sparsely vegetated, or vegetated with nonnative invasive species and when buffer enhancement is provided per the following criteria. Where buffer reduction with enhancement is permitted by this chapter, it shall be limited to portions of buffers that have minimal functions due to prior legal alteration.
1. The planning director shall only allow a buffer width reduction when the proposal includes a critical area and buffer enhancement plan that improves the functions of the buffer and the critical area.
2. A mitigation/enhancement plan shall be prepared in accordance with this chapter.
3. If a limited portion of the buffer has been previously legally altered and meets the criteria in this section, a buffer width reduction may be approved for that portion of the required buffer only.
4. The following criteria shall be used to determine when a required buffer is degraded and substantial legal alterations are present:
a. The required buffer area has been graded or substantially altered and has not been substantially revegetated (i.e., the buffer is covered with gravel, impervious surface, mowed lawn, or is vegetated with primarily invasive species such as reed canary grass, Himalayan blackberry, purple loosestrife, or other nonnative invasive species covering more than seventy-five percent of the buffer area).
b. Substantial clearing of the buffer was authorized and substantial revegetation with native species has not occurred.
c. A buffer that has been logged in the past but that has been revegetated with an overstory of willow, cottonwood, alder, evergreen, or mixed evergreen/deciduous overstory, and an understory shrub layer of noninvasive species does not constitute substantial alteration.
D. Riparian Wetland. Any stream adjoined by a riparian wetland shall have the buffer which applies to the wetland, unless the stream buffer requirement is more protective, in which case the stream buffer requirement shall apply.
E. Lake Buffers. Lakes have the following buffers of native vegetation:
If a wetland or stream occurs along the fringe of a lake, the buffer shall be the greater of that required for the lake or for the wetland or stream.
F. Buffers for Restored Stream Channels. When a culverted portion of a stream is proposed to be restored to an open channel, the buffer width shall be determined by the director following review of a critical area study. The study must include an analysis of the buffer width necessary to protect water quality and habitat functions of the stream.
G. Riparian Corridors. When a development is proposed on a lot with a disturbed riparian corridor, the city shall require that the habitat be enhanced by creating more diversity and eliminating any source of degradation, including, but not limited to:
1. Vegetative plantings of native or preferred wildlife food species;
2. Construction of nesting islands or installation of nesting boxes;
3. Removal of pollutant sources or fish movement blockages; or
4. Other actions necessary to enhance the viability of the riparian corridor for the benefit of wildlife habitat. (Ord. 3676-19 § 20, 2019; Ord. 2909-06 § 17, 2006.)