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Hopkins, Kristina (2014) FROM SMALL WATERSHEDS TO REGIONS: VARIATION IN HYDROLOGIC RESPONSE TO URBANIZATION. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Urbanization leads to a decline in the quality of aquatic ecosystems through the alteration of the natural hydrologic cycle. Existing conceptual models specify impervious surfaces as the dominant driver of hydrologic changes because impervious surfaces significantly alter the amount and timing of water flowing through aquatic ecosystems. However, existing models oversimplify how a natural watershed becomes degraded during urbanization, minimizing the spatiotemporal variability of urban stressors.
Urbanization gradients and long-term watershed studies are two approaches used to characterize hydrologic changes associated with development. Both approaches were used to quantify variability in the type of hydrologic changes among nine U.S. cities and to assess the human- and natural-factors driving regional differences in hydrologic response. Hydrologic analysis indicated an increase in the frequency of high flow events across all nine urbanization gradients. However, the severity of hydrologic change varied among cities and was not driven by inter-city differences in developed land-cover or impervious surfaces among gradients. Instead, physiographic setting best explained inter-city variability. Cities with glacial histories had less hydrologic change relative to development intensity when compared to cities without glacial histories. Glacial history sets a template of physical features (i.e., low relief and high water-storage) that can provide hydrologic buffering to dampen the runoff signature of high flow events. In conjunction with gradients, long-term watershed studies were used to identify the timing of flow alterations. Hydrologic and development datasets were used to reconstruct the dynamics of urbanization in seven study watersheds in three U.S. cities. In a Pittsburgh watershed, a hydrologic model indicated urbanization lead to a 50% reduction in water yield through the inter-basin transfer of stream water and urban runoff. Additional long-term watershed studies demonstrated abrupt shifts in stream flow and temporal lags in hydrologic response. The magnitude of hydrologic shifts was proportional to development intensity, whereas the timing of hydrologic shifts depended on interactions with perturbations such as extreme weather events and construction projects. The results from both approaches were used to construct a framework describing the range of physical and hydrologic changes associated with development, as well as major mechanisms that drive hydrologic change.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBain, Danieldbain@pitt.eduDBAIN
Committee MemberElliott, Emilyeelliott@pitt.eduEELLIOTT
Committee MemberRamsey, Michaelmramsey@pitt.eduMRAMSEY
Committee MemberAbad, Jorgejabad@pitt.eduJABAD
Committee MemberMehling,
Date: 19 September 2014
Date Type: Publication
Defense Date: 10 July 2014
Approval Date: 19 September 2014
Submission Date: 4 August 2014
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 161
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Geology and Planetary Science
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Hydrology, impervious surfaces, land-cover change, runoff, stream flow, urbanization
Date Deposited: 19 Sep 2014 18:46
Last Modified: 19 Sep 2019 05:15


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