Title page for ETD etd-07222011-150110


Type of Document Master's Thesis
Author Cranmer, Elizabeth Nadine
URN etd-07222011-150110
Title Effect of Urbanization on the Hyporheic Zone: Lessons from the Virginia Piedmont
Degree Master of Science
Department Environmental Engineering
Advisory Committee
Advisor Name Title
Hester, Erich T. Committee Chair
Moglen, Glenn E. Committee Member
Scott, Durelle Committee Member
Keywords
  • sediment
  • hydraulic conductivity
  • hyporheic
  • stream
  • urbanization
Date of Defense 2011-06-28
Availability restricted
Abstract
As the world’s population shifts toward living in cities, urbanization and its deleterious effects on the environment are a cause of increasing concern. The hyporheic zone is an important part of stream ecosystems, and here we focus on the effect of urbanization on the hyporheic zone from ten first-to-second-order streams within the Virginia Piedmont. We use sediment hydraulic conductivity and stream geomorphic complexity (vertical undulation of thalweg, channel sinuosity) as metrics of the potential for hyporheic exchange (hyporheic potential). Our results include bivariate plots that relate urbanization (e.g., total percent impervious) with hyporheic potential at several spatial scales. For example, at the watershed level, we observed a decrease in horizontal hydraulic conductivity with urbanization and an increase in vertical hydraulic conductivity, which ultimately results in a negligible trend from conflicting processes. Vertical geomorphic complexity increased with total percent impervious cover. This trend was somewhat unexpected and may be due to erosion of legacy sediment in stream banks. At the reach level, hydraulic conductivity increased and sinuosity decreased as the riparian buffer width increased; these trends are weak and are essentially negligible. The hydraulic conductivity results conform to expected trends and are a product of aforementioned concomitant processes. Our results emphasize the complexity of hydrologic and geomorphic processes occurring in urban stream systems at multiple scales. Overall, the watershed level effects enhancing hyporheic exchange, which is contrary to expectations. Given the importance of hyporheic exchange to stream function, further study is warranted to better understand the effects of urbanization.
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