Date of Award

2017

Document Type

Thesis

Department

Geography

First Advisor

Heejun Chang

Subjects

Daylighting, Land use management -- Oregon -- Portland, Watershed management, Stream ecology -- Oregon -- Portland

DOI

10.15760/honors.373

Abstract

Over the last 150 years, many urban areas have seen streams disappear underground into sewer systems and pipes. Stream burial, the rerouting of open channels to pipes and culverts, has a strong positive correlation with urban development. Patterns of development contributing to stream burial include the building of freeways, roads, sewer infrastructure, and residential housing. This study uses a combination of archival analysis, spatial analysis, and statistical methods to determine the patterns and impacts of stream burial in Portland, Oregon. Urban stream deserts have been identified in many metropolitan areas and can be defined as areas with dense urban development that have lost all hydrological connectivity. This study discusses the history of stream burial in Portland, delineates Portland's urban stream desert and identifies ecological impacts associated with stream burial. Spatial analysis shows the hotspots of stream deserts are concentrated in east Portland where both impervious areas and pipes are highly co-present. Water quality analysis is conducted by comparing five urban subwatersheds with varying degrees of burial and identifying the differences in water quality between upstream open channels and downstream buried reaches. While the ecological impacts of stream burial are not uniform, it can be argued that there is a relationship between stream burial and stream degradation. The results from the available data show significant differences between the upstream and downstream sites in three streams for several water quality parameters, and two streams that showed very little difference between upstream and downstream sites. The streams with the greatest variance in land use across the subwatershed had the most significant changes in water quality between the upstream and downstream sites. This study concludes by looking at stream daylighting as an option for both ecological restoration and social benefits. Recent efforts to design around existing nature and daylight streams in urban environments have contributed to improved water quality, increased biodiversity, community engagement, and reduced strain on aging sewer infrastructure.

Comments

An undergraduate honors thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in University Honors and Geography.

Persistent Identifier

http://archives.pdx.edu/ds/psu/20223

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