A Historical Analysis of Habitat Alterations in the Snohomish River Valley, Washington Since the Mid-19th Century: Implications for Chinook and Coho Salmon

Abstract

EXECUTIVE SUMMARY This report addresses salmonid habitat quantity and smolt production capacity in the Snohomish River estuary, floodplain and main stem from a historical perspective. The Snohomish River basin, located northeast of Seattle, Washington, is the second largest Puget Sound drainage. The Snohomish River, formed by the convergence of the Skykomish and Snoqualmie rivers, flows for 34 kilometers through a broad alluvial floodplain and estuary before entering Possession Sound between the Tulalip Indian Reservation and the city of Everett. Beginning in the mid-19th century, settlers cleared, drained, ditched and diked the Snohomish River valley. Snag boats removed wood obstructions to facilitate steamboat navigation. The cumulative impact of these actions has been dramatic losses and widespread degradation of salmonid habitat. Habitat loss and degradation, in turn, has reduced salmonid production capacity in the Snohomish River basin. Restoration and reconnection of lost habitat will play a major role in the recovery of threatened stocks. Understanding the type and extent of habitat loss is a fundamental component of restoring salmon runs. The historical context clarifies the causes of decline, provides a reference for desired future conditions and allows land managers to set clear goals for restoring lost and degraded habitats. Primary objectives of this report are: 1) to describe and quantify salmonid habitat alterations in the Snohomish River valley over the last 150 years; 2) to assess the impact of modified habitat conditions on the production potential of chinook (Oncorhynchus tshawytscha) and coho salmon (Oncorhynchus kisutch); 3) and to inform and guide the development of a restoration strategy through historical analysis. ...