Water Quality Impacts from Tidal Flooding in the Southern Chesapeake Bay

Title

Water Quality Impacts from Tidal Flooding in the Southern Chesapeake Bay

College

College of Sciences

Program

Ph.D. Oceanography

Publication Date

3-28-2019

Abstract

Little is known about the chemical and biological effects of flooding on adjacent aquatic environments. Terrestrial systems accumulate various types of compounds and debris that can potentially be carried in floodwaters into adjacent water bodies. In the Lower Chesapeake Bay, the incidence and duration of coastal flooding has increased due to the high relative rates of sea level rise in the region. While there are estimates of stormwater inputs into coastal systems, material (e.g., sediment, nutrients and contaminating bacteria) transported into the lower Chesapeake Bay as floodwaters recede have not been measured. Here, we report estimates of nutrient loads transported into a lower Chesapeake Bay sub-estuary in receding floodwaters during the 2017 King Tide (an extreme tide event). A total of 213 water samples were collected during the short time of the flood retreat. Particulate carbon and nitrogen (PCand PN, respectively), total suspended solids (TSS), and ammonium, nitrite, nitrate, urea, and phosphate concentrations where determined in all the samples while in 40 additional samples, Enterococcus abundance was determined. Water quality results were mapped with interpolations along the flooding extension. Inundation depths were extracted from GIS raster by computing difference with lidar-derived digital elevation model and water surface elevation for locations where water level sensors are located and water quality data were collected. Interpolation of the variables was done using Spline with Barriers, with a smoothing coefficient value of 0.2 and using a buffer line as an inland barrier, so that overland flood values are not interpolated over dry land. Interactive maps were built and loads were calculated based on these interpolations. The results of this study suggest that the nitrogen transported to adjacent estuarine systems during this single flooding event exceeded the total maximum annual load allocated for runoff to the Lafayette River sub-estuary alone.

Files

Water Quality Impacts from Tidal Flooding in the Southern Chesapeake Bay


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