Understanding the impacts of land cover change on water quality in an urbanized stream

Abstract

The heavily urbanized Johnson Creek watershed in the Portland, Oregon metropolitan region has experienced degraded water quality and historic mismanagement for decades. This paper reviews previous work on urbanized watersheds as well as studies that have explored Johnson Creek itself. Analysis of those previous studies is used to determine the present water quality within Johnson Creek and aims to predict how development and restoration will impact future water quality. While tracking water quality, stream temperature, total suspended solids (TSS), land cover metrics, extent of development, and canopy cover, this research expatiates on the effect of rising temperatures, the need for more responsive sediment transport, and increased spatial development within all portions of the watershed. Ultimately, this author has concluded that increased sunlight exposure through solar radiation loads on streams as a result of human-generated disturbances is a significant cause of stream temperature warming and the deterioration of water quality. Despite numerous and long-standing efforts for public-private cooperative stream restoration, the water quality in the Johnson Creek watershed continues to deteriorate. [Key Words] Water Quality, Land Cover Change, Urban Stream, Stream Restoration, Johnson Creek