30.62B.330 Erosion hazard areas - Channel migration zones

30.62B.330 Erosion hazard areas - Channel migration zones.

(1) This section establishes specific standards and requirements for development activities, actions requiring a project permit or clearing in channel migration zones adjacent to the following rivers:

River Name	River Sections (mi)
North Fork Skykomish River	0.00 - 8.64
North Fork Stillaguamish River	0.00 - 35.18
Pilchuck Creek	0.00 - 6.96
Pilchuck River	0.00 - 36.17
Sauk River	All
Skykomish River	0.00- 29.15
Snohomish River & Sloughs	All
Snoqualmie River	0.00 - 5.41
South Fork Skykomish River	0.00 - 6.71
South Fork Stillaguamish River	0.00 - 43.07
Stillaguamish River & Sloughs	All
Sultan River	0.00 - 7.64
Wallace River	0.00 - 7.71

(2) The department may require a channel migration zone study when a development activity or action requiring a project permit is proposed to occur in areas where evidence indicates channel migration is likely, in accordance with the following requirements:

(a) The study shall be conducted in accordance with Section 2 of the Forest Practices Board Manual (Title 222 WAC), Standard Methods for Identifying Bankfull Channel Features and Channel Migration Zones, November, 2004, except that areas behind natural or manmade features which limit channel migration that allow fish passage shall not be included in the channel migration zone;

(b) The study shall be performed under the direction of a qualified professional with experience in fluvial geomorphology or river hydraulics;

(i) a determination of the presence of channel migration, and if present, the delineation of the channel migration zone;

(ii) an analysis of the impacts of potential channel migration on the proposed development activity; and

(iii) an analysis of the impacts of the proposed development activity on the channel migration zone.

(3) Channel Migration Zone (CMZ) standards and requirements.

All development activities, actions requiring a project permit and clearing are prohibited in the channel migration zone, except as provided below:

(a) removal of hazardous trees;

(b) new utility facilities based on the following requirements;

(i) pipelines shall be bored 10 feet beneath the thalweg scour depth of the river within the CMZ;

(ii) surface utilities such as power transmission lines shall be located away from the current channel if feasible; and if not feasible, foundations within the CMZ shall be designed as in-channel structures if determined by the department to be necessary;

(c) new public bridges and transportation structures when no other feasible alternative exists or the alternative would result in unreasonable and disproportionate costs;

(d) boat ramps;

(e) normal maintenance or repair of existing flood control and bank stabilization structures, buildings, roads, bridges and utilities;

(f) shoreline and bank stabilization and flood protection measures pursuant to the general requirements contained SCC 30.62B.320(2);

(g) habitat restoration and enhancement projects;

(h) mitigation banks; and

(i) public parks intended to create or preserve open space, provide public access to shorelines of statewide significance, or provide passive recreation opportunities. For the purposes of this subsection, passive recreation may include, but is not limited to, memorials, interpretive facilities, seasonal primitive camping, and soft surface trails, as well as support infrastructure for those amenities, such as parking. All development subject to this subsection shall meet the following specific performance standards and be designed, to the greatest extent possible, to not inhibit channel migration:

(i) total impervious surface area shall not exceed the lesser of 10 percent of the site area or two acres;

(ii) the maximum footprint of any individual building shall not exceed 600 square feet, and the aggregate square footage of buildings on the site shall not exceed 2,400 square feet; and

(iii) improvements shall be removed or relocated if at any time the ordinary high water mark of the river channel is within two years of the average migration rate distance of such improvements. (Added by Amended Ord. 06-061, Aug. 1, 2007, Eff date Oct. 1, 2007; Amended by Amended Ord. 15-034, Sept. 2, 2015, Eff date Nov. 1, 2015; Amended by Ord. 19-022, June 26, 2019, Eff date July 8, 2019).