South Fork Snoqualmie Levee System Improvements

Overview

King County is conducting scientific analysis of the river dynamics, both geology and flooding, along the levied section of the South Fork Snoqualmie River (SFS) to identify areas of weakness or concern within the levee system and define alternative actions to address them.

The South Fork Snoqualmie Levee System Improvements project is identified in the 2006 King County Flood Hazard Management Plan. The project aims to strengthen the existing levee system to provide enhanced flood protection and reduce flood hazards in the heavily developed parts of the City of North Bend.

Timeline

Project Start - January 2010
Phase One Planning - February 2010
Phase Two Pre-Project Design and Feasibility
Phase Three Project Design
Phase Four Construction

Background

The upper Snoqualmie Valley has seen its share of floods over its developed history. We are in the process of analyzing the best way to optimize mitigation dollars within the Upper Snoqualmie basin which includes the North, South and Middle forks as well as the main stem Snoqualmie River. Our efforts for the south fork are focused on the levied system stretching from River Mile 2 to 7 upstream of I-90 to the river crossing at the Snoqualmie Valley Trail.

Extensive geotechnical deficiencies have been observed on the existing levee system along both banks of the South Fork Snoqualmie River through North Bend and the surrounding unincorporated areas. These problems can compromise the flood protection benefits of the levee system.

Interim activities

Post flood Inspection and repairs which require permitting and mitigation.
Maintenance and monitoring of existing levee system.
Flood warning center coordination and communication.

Goals

Improve performance of the levee system while minimizing environmental impacts and reducing long term costs of the flood hazard management through this reach.

For general project questions contact Chrys Bertolotto, Project Manager, River and Floodplain Management Section