Chapter 14.10
CHANNEL MIGRATION ZONES1
Sections:
14.10.010 Purpose.
Channel migration zones are identified by King County to reduce the risk of property or casualty loss due to stream bank destabilization, rapid stream incision, stream bank erosion, and shifts in location of stream channels. Figure 5, Special Flood Hazard Map2 identifies channel migration zones in the North Bend area. The city of North Bend does not regulate these channel migration zone areas. The city’s decision not to regulate the channel migration zones is based on the following facts:
The channel migration zones of the Middle Fork of the Snoqualmie River are identified as “avulsion” hazard channel migration areas associated with catastrophic flooding events by the 1996 King County Three Forks Snoqualmie River Channel Migration study. As such the potential channel migration would only occur in conjunction with a major flood event. In 2005, the flood insurance rate map was revised to incorporate and regulate the same general channel migration areas as floodways. The flood regulations provide substantially similar health and safety protection for the “avulsion” hazard channel migration areas, and the creation of duplicate, overlapping regulatory standards was not found to be in the best public interest by the city council.
The majority of the existing Silver Creek neighborhood affected by the channel migration zones of the Middle Fork of the Snoqualmie River is already developed in public open space ownership, or protected by existing public roadways that will likely be restored if ever damaged by a major flood event, including a channel migration by “avulsion.”
The remaining large parcels of land that may be developed in the Silver Creek neighborhood are likely to be reviewed under the SEPA process, and any channel migration zones of the Middle Fork of the Snoqualmie River identified as “avulsion” hazard channel migration areas that are not regulated by the flood regulations can be addressed and mitigated in the SEPA process.
The channel migration zones of the South Fork of the Snoqualmie River are identified as lateral migration hazard areas in the 1996 King County Three Forks Snoqualmie River Channel Migration study. The areas at risk are wholly located in the Tollgate Farm public open space purchased in part to protect them from development because of the risk associated with the critical areas on the property. As with the Silver Creek residential areas, the floodways on the 2005 FIRM cover similar areas to the channel migration areas and if any development was proposed on the public open space it likely would be reviewed under the SEPA process. In the SEPA process any avulsion channel migration zones of the South Fork or Middle Fork of the Snoqualmie River that are not regulated by the flood regulations could be addressed and mitigated. (Ord. 1243 Exh. B (part), 2006).
Prior legislation: Ords. 912, 929, 1048, 1053, 1088, 1166, 1171 and 1172.
See city website for current version.