This project integrates analysis of remote-sensing data, field surveys and mapping, and fluvial models to test hypotheses of the fundamental controls on stream form and process in the deglaciated landscape of northern New England. Rivers in regions covered by late Pleistocene continental glaciers evolve through a combination of bedrock erosion, availability and transport of bedload, and ecological succession. Stream morphology, and therefore habitat suitability, varies in the downstream direction, depending on local sedimentary sources and sinks. Historical land-use change from deforestation to riparian protection further influences fluvial processes. At present, motivated by the near extirpation of Atlantic salmon in Maine, non-profit groups and government agencies are working to reverse fluvial habitat degradation by stabilizing watershed sediment inputs and removing dams. However, these restoration efforts are typically guided by geomorphic studies of salmon rivers in other regions. This proposal seeks to understand the trajectory of landscape response to changes in land use, and develop and test spatial numerical models that relate stream physical processes to habitat quality.
Airborne laser swath mapping (ALSM) will expand the advances made in quantitative geomorphology using digital elevation models (DEMs) over the past 15 years. ALSM surveys yield high-resolution measurements of "bare-earth" topography, thickness of forest cover, and water depth over entire watersheds. This study will collect ALSM data from three watersheds in Maine and use channel morphologic measurements as input for numerical models of transport processes. These spatial models will be tested through comparison to field surveys, geological and ecological mapping, fish-population datasets, and past conditions using historical aerial photographs.
Teams of undergraduate and Master's students will conduct the research, working together on each of the watersheds using field, geospatial, and numerical methods. Each student will have a role within the team that evolves to eventual production and presentation of research projects. Multi-year student involvement will ensure strong professor-student, graduate-undergraduate, and undergraduate-undergraduate mentoring. The proposed research is directly relevant to ongoing ecosystem restoration projects in northern New England. All phases of this study will include direct outreach by students and the PI to share results and methods with land managers, watershed restoration non-profit groups, high school students, and other scientists from a variety of fields in forums from field workshops to national meetings. These efforts will include specific recommendations, based on research findings, for optimizing future restoration projects. Through interactions with community-based groups, students will gain an appreciation for the challenges of land-management decision-making processes. This exchange between students and stakeholders will ensure that the research has a strong societal and scientific impact.
This project was an integrated analysis of remote-sensing data, field surveys and mapping, and fluvial models to test hypotheses of the fundamental controls on stream form and process in the deglaciated landscape of northern New England. Rivers in regions covered by late Pleistocene continental glaciers evolve through a combination of bedrock erosion, availability and transport of bedload, and ecological succession. Stream morphology, and therefore habitat suitability, varies in the downstream direction, depending on local sedimentary sources and sinks. Historical land-use change from deforestation to riparian protection further influences fluvial processes. At present, motivated by the near extirpation of Atlantic salmon in Maine, non-profit groups and government agencies are working to reverse fluvial habitat degradation by stabilizing watershed sediment inputs and removing dams. However, these restoration efforts are typically guided by geomorphic studies of salmon rivers in other regions. This proposal worked to understand the trajectory of landscape response to changes in land use, and develop and test spatial numerical models that relate stream physical processes to habitat quality. The project participants used high-resolution digital topographic data from three low-relief watersheds in Maine to understand the evolution of channel form and habitat quality in response to deglaciation and land-use changes. The study demonstrated the power of using new digital elevation data to study channel processes. High-resolution topographic datasets allow geomorphologists to make measurements of channel form (e.g., slope, width) over entire watersheds, at a resolution previously available over smaller lengths of streams via time-consuming field surveys. These factors dictate flow and transport processes, and their spatial variability influences the distribution and quality of riparian habitat. Large suites of morphologic measurements enabled us to collect statistically robust datasets to test process-based models of the controls on channel form as climate and land use changes. One specific research outcome from this project was to provide stream practitioners with tools to evaluate which parts of a given watershed will benefit most from restoration, based on knowledge of stream processes and history, via analysis of lidar DEMs. The first step in this process was a careful, field-based analysis of the controls on river substrate mobility in key locations in the study river systems, which was published in Geomorphology in 2008. The second step was to understand controls (e.g., bedrock geology, glacial history, land use) on the variability of channel processes and morphology via longitudinal field-based stream surveys. A manuscript published in River Research and Applications in 2011 worked in this direction by quantitatively comparing channel morphology and salmon habitat characteristics of a river in Maine with one in northern New Brunswick. The third step was the development of algorithms to make geomorphic measurements from high-resolution geospatial data, as explored in a 2009 Eos article. The fourth step was model development and testing, which was presented in a 2013 Geological Society of America Bulletin article. Broader Impacts The project research team consisted of Masters students (entering through third year) and undergraduate students (first through fourth year). The evolving group worked together extensively in the field during the summers of 2007-2013, and continued to meet regularly during the academic years at Boston College. Student mentoring was central to the goals of this project. Project Masters and Bachelors students made more than 20 presentations (poster and oral) at various scientific and management conferences, were co-authors on seven peer-reviewed publications. We held a field workshop where project students worked with high-school students from Washington Academy in East Machias, Maine. In addition, the student participants and the PI worked actively to keep watershed non-profit groups informed of our progress and findings by making presentations at meetings (such as the Maine Water Conference and NSF-sponsored Diadromous Species Restoration Research Network meetings), seeking involvement of interested volunteers during field operations, and leading field trips. The scientific findings of this study have already had a direct effect on how watershed groups spend their resources, which is a key measure of project success. This study also developed process-based geographic information systems models that aid in identification of channel reaches that are good candidates for habitat restoration based on their predicted ability to transport sediment.
