Thesis (Ph.D.)--York University, 2005. Graduate Programme in Education. / Typescript. Includes bibliographical references (leaves 170-179). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://proquest.umi.com/pqdweb?index=0&did=1126759811&SrchMode=1&sid=22&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1195575878&clientId=5220

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Appendix A: Standard errors of annual discharge and change in reservoir content data from selected stations in the lower Colorado River streamflow-gaging station network, 1995-99 (Water-resources investigations report no.01-4240) Includes bibliographical references (leaf 44).

Thesis (Ph. D.)--Oregon State University, 1993. / Typescript (photocopy). Includes bibliographical references (leaves 155-173). Also available via the World Wide Web.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 128-136). Also available via the Internet.

Thesis (M.S.)--Oregon State University, 1990. / Typescript (photocopy). Includes bibliographical references (leaves 88-100). Also available via the World Wide Web.

Thesis (Ph.D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 325-365) Also available in print.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 148-163).

No description available.

This dissertation is a study of the relationships between nitrogen (N) availability and spiraling (the paired processes of nutrient cycling and advective transport) in stream ecosystems. Anthropogenic activities have greatly increased rates of N loading to aquatic ecosystems. However, streams may be important sites for retention, removal, and transformation of N. In order to identify controls on NO3-N spiraling in anthropogenically impacted streams, I examined relationships among NO3-N spiraling and a suite of chemical, physical, and biological variables in streams spanning a gradient of N concentration. Across all streams, gross primary production (GPP) accounted for most NO3-N demand. Uptake of NO3-N was also related to GPP but was limited by N availability when N concentrations were low. A combination of GPP and NO3-N explained 80% of the variance in uptake. In chapter 3, I conducted a series of short-term nutrient releases in which streamwater NO3-N concentration was incrementally elevated to identify conditions leading to saturation of uptake capacity. Four of six study streams showed signs of N limitation whereas there was no significant change in uptake with increasing NO3-N amendment in two streams, suggesting N saturation. Proximity to saturation was generally correlated to N concentration but was also predicted by the ratio of N:P. My results suggest complex relationships between N spiraling and availability that depend on resident biota and other limiting factors. In chapter 4, I examined nutrient spiraling methodology by comparing differences between ambient and amendment-derived NO3-N spiraling metrics. I quantified spiraling metrics during a short-term NO3-N amendment and under ambient conditions using a stable isotope (15NO3-N) tracer. Uptake lengths measured during amendments were consistently longer than ambient uptake lengths. Amendment-derived NO3-N uptake velocity and uptake were underestimated relative to ambient conditions. Using a technique to estimate ambient uptake length extrapolated from the relationship between uptake length and nutrient amendment concentration for a series of amendments at different concentrations, I found that extrapolated uptake lengths were generally better predictors of ambient uptake lengths than amendment-derived uptake lengths but the technique was less effective in high N streams that showed signs of weak N limitation. / Ph. D.

The stream restoration industry has been growing since the addition and modification of Section 404 to the Clean Water Act. Many projects follow the guidelines of Natural Channel Design and use in-stream structures to stabilize stream channels. Post-project monitoring rarely exceeds 3-5 years, and the lack of guidance, funding, and pre-restoration data prevents meaningful post-project assessment of the design techniques. The Virginia Tech Stream Research, Education, and Management (StREAM) Lab is a research facility where a stream restoration project was completed along 1.3 km of Stroubles Creek in 2010. The study site provides a unique opportunity to compare the use of three restoration treatments with different intensities of restoration actions. Following exclusion of cattle from all three sites, the first treatment reach was left to naturally revegetate (Treatment 1) and along Treatment 2 the streambanks were re-graded to a 3:1 slope and replanted. An additional inset floodplain was constructed within the active channel of Treatment 3. Pre-restoration data, including topographic surveys and erosion pin measurements, provided a baseline for quantification of morphological response 11 years post-restoration. This project utilized as-built survey data from 2010 and a follow-up survey in 2021. The spatial data were analyzed to quantify important stream metrics: cross-sectional area, width, maximum depth, hydraulic depth, and width-to-depth ratio. Overall, the percent change per year of each metric decreased substantially following the restoration, indicating an increase in stability. While Treatment 3 continues to show minor erosion on average (+3.3% in area, +3.2% in width, and +11.2% in maximum depth), Treatments 1 (excluding cross section 5) and 2 decreased on average in area (-3.4% and -18.6%) and hydraulic depth (-13.3% and -10.8%). Treatment 1 eroded by an average of 11.7% in width compared to a decrease of -13.4% in Treatment 2 and an increase in 3.2% in Treatment 3. Comparisons of each treatment to Virginia Mitigation Banking Standards indicated Treatment 1 met the fewest number of criteria, followed by Treatment 2 and then Treatment 3, indicating that hard structures are not necessary to meet mitigation bank standards, even in urban watersheds. In an urban, incised channel with cattle impacts, re-grading the streambanks, actively planting woody riparian vegetation, and incorporating an inset floodplain will accelerate the establishment of channel stability, as compared to the more passive approach of simply removing cattle access to the channel. / Master of Science / The stream restoration industry has been growing since the addition and modification of Section 404 to the Clean Water Act. Specific design models, such as Natural Channel Design which focuses heavily on preventing the stream from moving using stone and wood structures, guide many projects. Post-project monitoring rarely exceeds 3-5 years, and the lack of guidance, funding, and pre-restoration data prevents meaningful post-project assessment of the design techniques. The Virginia Tech Stream Research, Education, and Management (StREAM) Lab is a research facility in which human interactions in the Stroubles Creek Watershed can be evaluated. A stream restoration project was completed on Stroubles Creek at the StREAM Lab property in 2010. This project provides a unique opportunity to compare three different intensities of restoration actions. Following exclusion of cattle from all three sites, plants were left to naturally regrow in the first treatment reach and Treatment 2 re-shaped the banks to a gentler slope and replanted. Like Treatment 2, an additional inset floodplain was constructed within the active channel of Treatment 3. Pre-restoration data, including topographic surveys and bank erosion measurements provided a baseline for quantification of physical response 11 years post-restoration. This project utilized survey data from immediately post-restoration in 2010, and a follow-up survey in 2021. The surveys were analyzed using AutoCAD Civil3D and cross-sectional area, width, maximum depth, hydraulic depth (area/top width), and width-to-depth ratio were calculated. Overall, the percent change per year of each metric decreased substantially following the restoration, indicating an increase in stability. While Treatment 3 continues to show minor erosion (+3.3% in area, +3.2% in width, and +11.2% in maximum depth), Treatments 1 (excluding cross section 5) and 2 decreased on average in area (-3.4% and -18.6%) and hydraulic depth (-13.3% and -10.8%). Treatment 1 eroded by an average of 11.7% in width compared to a decrease of -13.4% in Treatment 2 and an increase in 3.2% in Treatment 3. Comparisons of each treatment to Virginia Mitigation Banking Standards indicated Treatment 3 met the highest number of criteria, followed by Treatment 2 and then Treatment 1, indicating that hard structures are not necessary to meet mitigation bank standards, even in urban watersheds. In an urban, incised channel with cattle impacts, regrading the streambanks, actively planting woody riparian vegetation, and incorporating an inset floodplain will accelerate the establishment of channel stability, as compared to the more passive approach of simply removing cattle access to the channel.