Date of Award

Summer 8-2023

Document Type


Degree Name

Doctor of Philosophy (PhD)


Ocean & Earth Sciences



Committee Director

Margaret R. Mulholland

Committee Member

Jon Derek Loftis

Committee Member

Sophie Clayton

Committee Member

Tom R. Allen


Many coastal areas around the globe suffer from nutrient pollution and its environmental, social, and economic consequences. Nutrient inputs can come from point (e.g., the end of a pipe) and nonpoint sources, from which the former are better constrained as sampling need only be conducted at a discharge point. Given the temporal and spatially extensive nature of tidal flooding events, they can represent another type of nonpoint source of nutrients to adjacent water bodies heretofore, unexamined and quantified. Most studies examining impacts of tidal flooding have focused on threats to resources on land, such as urban infrastructure and human health and wetlands. However, little is known about water quality impairments to adjacent aquatic ecosystems that result from recurrent tidal flooding in urban areas as materials (e.g., sediment, nutrients, and contaminating bacteria) are transported into local and regional waterways as floodwaters recede. Here, I present a multi-year study that provides the first quantitative assessment of the spatial and temporal extent of nutrient and fecal material loading during tidal flooding. The first chapter describes the rationale behind this study and previous research on the topic; the second chapter covers in detail the first citizen science approach I used to collect multiple floodwater samples during a single flooding event; the third chapter is a summary of five years of that research and how results point to floodwater events as a nonpoint sources for dissolved nitrogen and phosphorous; the fourth chapter reports results from more frequent sampling at sentinel sites to establish variability in these nutrient loads; and the fifth, and last chapter, summarizes the importance of these results scientifically, but also societally, and with a discussion about future research needs. Overall, results indicate that tidal flooding events are quantitatively significant but previously unquantified sources of nutrients to adjacent water bodies that will increase as the intensity of flooding increases over time. Measurements of fecal indicators in floodwater samples suggest that there is also a health risk for people in contact with floodwaters. Results suggest that tidal flooding needs to be considered when establishing restoration goals and setting limits for nonpoint source loading of dissolved nutrients to the Chesapeake Bay.


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