marshasa@onid.orst.edu

My research interests include cumulative impacts of land use conversion on hydrologic storage and runoff, sustainable development, urban storm water management, wetland hydrology, and environmental flows. 

Personal interests include native plant gardening, telemark skiing, road and mountain biking, whitewater kayaking, and canoeing.

Environmental flows refer to the range of stream flows necessary to sustain native aquatic ecosystems.  Several factors, including dam regulation, irrigation withdrawals and land cover change, have been implicated in modification of environmental flows.   Of these factors, the conversion of vegetated land to impervious surfaces can modify the timing, duration, magnitude and frequency of flow events, resulting in altered channel geometry, aquatic species composition, and sediment transport.  Across the United States, many agricultural lands are ceded for urban development in order to accommodate a growing human population.  While agricultural lands are often associated with ecological disturbance (e.g. excess nutrients, pesticides and sediment; invasive species), they can offer a set of ecosystem services and hydrological variability distinct from nearby urban areas.  Past research has focused on selected hydrologic components in tandem with land cover change, but few studies have used a consistent set of ecologically meaningful hydrologic parameters to detect major hydrologic changes with land use conversion across a larger geographic region.  Using meta-analysis techniques and Indices of Hydrologic Alteration, we compare a set of environmental flows parameters across agricultural-urban land use gradients in order to better understand how change in managed land use influences the hydrology and ecology of small, urbanizing lowland stream systems across the US.  We then propose a set of metrics that are reliable in detecting flow regime alteration associated with agricultural to urban land conversion.