Dissertation/Thesis Abstract

Dynamics of Channel Complexity and Nitrate Retention in Upper Fanno Creek, Oregon
by Bean, Robert Allen, M.S., Portland State University, 2012, 83; 1518608
Abstract (Summary)

This study investigates the relationship between channel complexity and nutrient spiraling along 31 reaches of an urbanized watershed in Portland, Oregon. Much research shows that urbanization has an effect on watershed hydrology and nutrient loading at the watershed scale for various sized catchments. However, the flux of nutrients over short reaches within a stream channel has been less studied because of the effort and costs associated with fieldwork and subsequent laboratory analysis of the surface water samples. In this study I measure channel complexity and uptake velocity of nitrate to determine if this relationship is indicative of a healthy, functioning stream. I take field measurements and samples to determine the complexity and uptake velocity of each reach. Using ion-selective electrodes, the fluxes of nitrate were measured within each reach; when combined with channel geometry and velocity measurements these measurements allow for the transformation of nitrate fluxes into spiraling metrics. Results show that 18 of the 31 reaches had uptake velocity. Discharge and sinuosity were positively correlated with nitrate uptake velocity. Complexity and nitrate concentration were negatively correlated with nitrate uptake velocity. Grass landcover was positively correlated with nitrate uptake velocity and negatively correlated with nitrate concentration. These results indicate that land use and channel complexity both are related to the in-stream processing of nitrate. The implication of this study is that channel complexity is an important driver of nutrient flux in an urban watershed, and that this technique can be applied in future studies to better characterize water quality of stream channels over short reaches to entire catchments.

Indexing (document details)
Advisor: Lafrenz, Martin
Commitee: Chang, Heejun, Harvey, Thomas
School: Portland State University
Department: Geography
School Location: United States -- Oregon
Source: MAI 51/02M(E), Masters Abstracts International
Source Type: DISSERTATION
Subjects: Hydrologic sciences, Biogeochemistry, Geomorphology
Keywords: Channel complexity, Fluvial geomorphology, Nitrate, Riparian function, River restoration, Transient storage
Publication Number: 1518608
ISBN: 9781267609649
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