Presentation Title

Putting beavers into urban streams to improve water quality

Streaming Media

Start Date

2-3-2021 11:55 AM

End Date

2-3-2021 12:05 PM

Abstract

While many different watershed management strategies have been implemented to improve water quality, relatively few studies empirically tested the combined effects of different strategies on water quality in relation to land cover changes using long-term empirical data at the sub-basin scale. Using 10 years of TSS data, we examined how the conversion of wetland, wetland fragmentation, beaver dams, and Best Management Practices (BMPs) are related to wet season TSS concentrations for the 12 sub-basins of the Tualatin River basin in the Portland metropolitan region. We used geographic information systems, Fragstat, and correlation analysis to identify the direction of land cover change, degree of wetland fragmentation, and the strength of the relationship between TSS change and explanatory variables. Our findings show that, regardless of urban development, there was some improvement in TSS concentrations, with increases in wetland size and the presence of beaver dams, particularly during the mid-wet season when flows were highest. Other BMPs effectively reduced TSS concentrations for the early and late-wet seasons when flows were not as high as in the middle wet-season. Aggregated wetlands were more effective for improving water quality than smaller disaggregated wetlands of similar total area when combined with beaver dams and BMPs. The findings offer important practical policy implications for urbanizing watersheds that seek to improve water quality with development.

Subjects

Hydrology, Land/watershed management, Water quality

Persistent Identifier

https://archives.pdx.edu/ds/psu/35502

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Mar 2nd, 11:55 AM Mar 2nd, 12:05 PM

Putting beavers into urban streams to improve water quality

While many different watershed management strategies have been implemented to improve water quality, relatively few studies empirically tested the combined effects of different strategies on water quality in relation to land cover changes using long-term empirical data at the sub-basin scale. Using 10 years of TSS data, we examined how the conversion of wetland, wetland fragmentation, beaver dams, and Best Management Practices (BMPs) are related to wet season TSS concentrations for the 12 sub-basins of the Tualatin River basin in the Portland metropolitan region. We used geographic information systems, Fragstat, and correlation analysis to identify the direction of land cover change, degree of wetland fragmentation, and the strength of the relationship between TSS change and explanatory variables. Our findings show that, regardless of urban development, there was some improvement in TSS concentrations, with increases in wetland size and the presence of beaver dams, particularly during the mid-wet season when flows were highest. Other BMPs effectively reduced TSS concentrations for the early and late-wet seasons when flows were not as high as in the middle wet-season. Aggregated wetlands were more effective for improving water quality than smaller disaggregated wetlands of similar total area when combined with beaver dams and BMPs. The findings offer important practical policy implications for urbanizing watersheds that seek to improve water quality with development.