Drafter
Clerk 06/11/2014
Title
AN ORDINANCE establishing a demonstration project, as authorized under K.C.C. chapter 21A.55, for alluvial fan management pilot projects located outside areas of shoreline jurisdiction.
Body
BE IT ORDAINED BY THE COUNCIL OF KING COUNTY:
SECTION 1. Findings:
A. Alluvial fans occur where streams carrying sediment change from a steeper slope to a flatter slope and lose their capacity to move sediment and sediment drops out of the water column. Alluvial fans fill in the existing stream channel and force the stream to another location creating the characteristic fan shape over time. When a stream is forced out of its channel on developed alluvial fans, it damages infrastructure such as roads, structures and utilities, as well as flooding surrounding property.
B. Alluvial fans are the result of dynamic physical processes and in many cases provide beneficial ecosystem services such as multithreaded stream channels with slow-moving water and abundant food for rearing fish. For example, the alluvial fans of the Tolt and Raging rivers are very high priority salmon habitat. They are also a component of landslide hazard areas as defined in K.C.C. 21A.06.680 and are regulated under King County's critical areas regulations in K.C.C. chapter 21A.24.
C. Because much of the county's farmland is located in valley floors below relatively steep valley walls, many of the county's farms are impacted by alluvial fans. Alluvial fans fill agricultural drainage channels as a result of both normal ongoing deposition of sediment and larger episodic deposition events, which deposit upslope sediment and debris in agricultural fields.
D. In addition to being used for farming operations, many alluvial fans have been developed with residential structures or with infrastructure, or are used for recreational purposes.
E. King County's existing regulations and the lack of approved management practices make it difficult to remedy the im...

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