The Local Impacts of Road Crossings on Puget Lowland Creeks

Abstract

Urbanization in the Puget Sound region continues to place mounting strain on natural fluvial systems. As one component of urbanization, the road network is commonly recognized to be a significant stressor of physical stream-channel processes. Several studies have considered the effects of forest roads on creeks in mountainous and/or logged areas, but few have examined the impacts of road crossings on lowland creeks, where most urban development is concentrated. This project provides an analysis of the local effects of road crossings on Puget Lowland creeks. This analysis was conducted through three interrelated studies having four objectives: 1) developing methods for measuring local road-crossing impacts to physical channel conditions; 2) determining specific physical processes and conditions altered by road crossings; 3) determining what road-crossing characteristics contribute to downstream alterations; and 4) assessing the significance of local road-crossing impacts relative to basin-wide urbanization impacts.