Using Regional Data Sets to Study Source to Sink Sedimentary Processes

• Main Author: Gunnell, John
• Format: Thesis
• Language: English
• Published: The University of North Carolina at Chapel Hill University Libraries 2016
• Subjects: Northwest Atlantic
• Online Access: https://dx.doi.org/10.17615/469e-fx03; https://cdr.lib.unc.edu/concern/dissertations/rr171x68r?locale=en

The study of sediment provenance, transport, and deposition encompasses a diverse set of geomorphological settings and processes. For a variety of reasons, “source to sink” sedimentary systems have historically been difficult to characterize due to operational limitations of the scientists studying them. Consequently, these systems are understood through the comparison of small-scale observational case studies. This lack of quantitative unity between studies has stymied attempts at building generalizable theory. The purpose of this dissertation is to reevaluate some longstanding intuitions in the field of sedimentary geomorphology by taking a broader vantage and integrating observations from expansive regional scopes into unified frames of reference. This undertaking has revealed important insights about the behavior of several source to sink systems that would not have been noticeable if they were studied in a narrower context. An overview of these insights by chapter is as follows: Chapter 1: As would traditionally be expected, coastal emergent wetland inventories showed significant individual correlations with respect to wave energy and relief. Terrestrial sediment flux to the ocean, on the other hand, apparently only contributes to large scale wetland abundance when present above a threshold quantity. This suggests that estuarine processes in the vicinity of wetlands play a larger role in promoting marsh abundance than fluvial sediment supply does. Chapter 2: Despite the complex cascade of expected landscape responses to urbanization, suspended sediment yields of U.S. Piedmont streams consistently were an order of magnitude higher in watersheds with spatial indices of extensive population growth and urban development. Chapter 3: A comparison between modeled and measured sediment properties of marsh cores along the Northwest Atlantic coast showed that the contemporary modeling paradigm of marsh accretion can occasionally reproduce actual marsh soil characteristics. Nevertheless, rapidly subsiding Louisiana marshes as well as marshes with extreme values in organic matter density systematically deviated from modeled expectations. Current models fail to parameterize potentially important aspects of accretion and compressibility in a large number of wetlands across the United States, casting doubt on our current capacity to reasonably predict marsh vertical response to accelerated sea level rise in a variety of locations.