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Abstract Extreme precipitation during Hurricane Florence, which made landfall in North Carolina in September 2018, led to breaches of hog waste lagoons, coal ash pits, and wastewater facilities. In the weeks following the storm, freshwater discharge carried pollutants, sediment, organic matter, and debris to the coastal ocean, contributing to beach closures, algae blooms, hypoxia, and other ecosystem impacts. Here, the ocean pathways of land‐sourced contaminants following Hurricane Florence are investigated using the Regional Ocean Modeling System (ROMS) with a river point source with fixed water properties from a hydrologic model (WRF‐Hydro) of the Cape Fear River Basin, North Carolina's largest watershed. Patterns of contaminant transport in the coastal ocean are quantified with a finite duration tracer release based on observed flooding of agricultural and industrial facilities. A suite of synthetic events also was simulated to investigate the sensitivity of the river plume transport pathways to river discharge and wind direction. The simulated Hurricane Florence discharge event led to westward (downcoast) transport of contaminants in a coastal current, along with intermittent storage and release of material in an offshore (bulge) or eastward (upcoast) region near the river mouth, modulated by alternating upwelling and downwelling winds. The river plume patterns led to a delayed onset and long duration of contaminants affecting beaches 100 km to the west, days to weeks after the storm. Maps of the onset and duration of hypothetical water quality hazards for a range of weather conditions may provide guidance to managers on the timing of swimming/shellfishing advisories and water quality sampling.
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Participatory science for coastal water quality: freshwater plume mapping and volunteer retention in a randomized informational intervention
Among the biggest threats to coastal water quality are freshwater discharges. It is difficult to predict the spatial extent of freshwater plumes at marine beaches because processes governing mass transport in the surf zone are complex. Participatory science approaches could facilitate collecting shoreline data, although volunteer sampling campaigns can be challenged by data quality and volunteer retention. The goals of this study were to (1) work with volunteers to estimate safe swimming distances at beaches that receive polluted discharges, and (2) test whether informational feedback to volunteers increased retention. Forty-six volunteers participated over 12 weeks in 2019 by collecting 1452 salinity measurements at beaches near the mouths of two Central California freshwater discharges and completing participation surveys. These measurements resulted in 145 distinct estimates of safe swimming distances ( D 90 ), spanning a range of environmental conditions during rainy and dry periods. Median D 90 s were 150 and 100 m at San Pedro Creek south and north, and 490 and 330 m at San Lorenzo River west and east, respectively. D 90 was significantly associated with adjacent freshwater discharge rate at both discharges and tide level at one discharge. On average, the odds of volunteers conducting sampling decreased by 4% (95% CI: 1%, 7%) with each successive week. A randomized intervention providing repeated data feedback via email to volunteers did not affect their retention in the study.
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- Award ID(s):
- 1644300
- PAR ID:
- 10143453
- Date Published:
- Journal Name:
- Environmental Science: Processes & Impacts
- ISSN:
- 2050-7887
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9em00571d
