Date of Award

Fall 12-21-2018

Level of Access

Open-Access Thesis

Language

English

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

Advisor

Sean Smith

Second Committee Member

Damian Brady

Third Committee Member

Hamish Greig

Additional Committee Members

Shaleen Jain

Bob Prucha

Andrew Reeve

Abstract

This dissertation summarizes research examining watershed processes across Northern New England, with an emphasis on the Central and Coastal regions of Maine. The research presented here focuses on the linkages between watershed geomorphic conditions, climate, and surface flow regimes driving stream channel hydraulic conditions and bed dynamics governing channel geometry. The geologic and human history of the landscape provides the context in which earth surface processes are examined within the dominant physiographic settings in Maine to describe vulnerabilities to climate change. Results are summarized to support the development of sustainability solutions for forecasted watershed management problems by natural resource management agencies and communities.

The research components of this dissertation were developed through stakeholder engagement to identify regional water resource sustainability problems. Physical watershed processes affecting stream flow and sediment transport conditions are fundamental to stakeholder concerns. This research examines the influence from human activities, climate, and earth surface processes associated with erosion from ice and water flows on modern surface hydrology and fluvial geomorphology in the region. Research targets are organized relative to scientific principles and contemporary watershed management approaches relevant to stakeholder interests related to water quality, aquatic habitat, recreation, and coastal fisheries.

This research is framed by geo-spatial analyses organized to examine Northern New England landscape conditions linked to patterns of surface water flow. The approach uses dominant geologic, soil, topographic, and land cover conditions as independent variables, providing a tool for scaling observations in reference watersheds and evaluating the transferability of information guiding selection of watershed management practices across the region. River discharge measurement data within representative assemblages are analyzed to evaluate the implications of varied landscape conditions to surface water flow regimes. Stream channel hydraulic geometry is quantified to relate surface flows, stream channel conditions, and the history of glaciation and human activities affecting watershed processes.

Flow regime responses to forecasted climate change in varied landscape settings are estimated using numerical watershed hydrologic simulations. Modeling results suggest that changes to annual snow pack conditions will have the most substantial influence on surface flows. Base, mid-range, and peak flows have varied responses governed by surface water storage, snow pack dynamics, and rainfall patterns. The impact of the predicted surface flow changes on stream channel sedimentary environments are quantified by coupling simulated flow time series with a sediment transport model. Results indicate that changes to sediment dynamics affecting stream hydraulics and channel stability may result from forecasted climate changes in the region.

Research objectives and outcomes are framed to support the development of sustainability solutions to watershed management challenges related to public safety, water quality, and aquatic habitat conservation. The process of designing the project approach with input from stakeholders and evaluating outcomes from quantitative analyses improves understanding of how multiple factors governing earth surface processes operating over varied time scales combine to create varied hydrologic and geomorphic responses to watershed land use and climate changes in the Northern New England region. The prediction of measurable alterations to streams in evaluated settings provide rationale for development of watershed management strategies in response to future land use and climate changes. Varied vulnerabilities to changes suggest that customized management approaches will be necessary as some stream systems will be more responsive than others. The development of an approach for parsing the landscape into Geomorphic Response Units (GRUs) demonstrated by this research provides a basis for designing a statewide approach for implementing strategies for watershed management that considers varied vulnerabilities to land use and climate changes in the region. This work provides tools for the stakeholder community to evaluate the applicability of management techniques across the region and knowledge of water resource vulnerabilities as they relate to landscape conditions and climate.

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