Fecal bacteria contamination of floodwaters and a coastal waterway from tidally-driven stormwater network inundation
Data files
Apr 05, 2024 version files 317.62 MB
Abstract
Inundation of coastal stormwater networks by tides is widespread due to sea-level rise (SLR). The water quality risks posed by tidal water rising up through stormwater infrastructure (pipes and catch basins), out onto roadways, and back out to receiving water bodies are poorly understood but may be substantial given that stormwater networks are a known source of fecal contamination. In this study, we (1) documented temporal variation in concentrations of Enterococcus spp. (ENT), the fecal indicator bacteria standard for marine waters, in a coastal waterway over a two-month period and more intensively during two perigean spring tide periods, (2) measured ENT concentrations in roadway floodwaters during tidal floods, and (3) explained variation in ENT concentrations as a function of tidal inundation, antecedent rainfall, and stormwater infrastructure using a pipe network inundation model and robust linear mixed effect models. We find that ENT concentrations in the receiving water body vary as a function of tidal stage and antecedent rainfall, but also site-specific characteristics of the stormwater network that drains to the waterbody. Tidal variables significantly explain measured ENT variance in the waterway, however, runoff drove higher ENT concentrations in the receiving waterway. Samples of floodwaters on roadways during both perigean spring tide events were limited, but all samples exceed thresholds for safe public use of recreational water. These results indicate that inundation of stormwater networks by tides could pose public health hazards in receiving water bodies and on roadways, which will likely be exacerbated in the future due to continued SLR.
README: Fecal bacteria contamination of floodwaters and a coastal waterway from tidally-driven stormwater network inundation
https://doi.org/10.5061/dryad.sxksn039s
Description of the data and file structure
This dataset includes four data types:
Water quality data: Enterococcus spp. (ENT) concentrations enumerated using the IDEXX Enterolert standard protocol with the Quanti-tray 2000 (IDEXX, ASTM Method D6503-99). Data from baseline conditions are in the file idexx_baseline.csv; data from perigean conditions are in the file idexx_perigean.csv, and all data including floodwater ENT concentrations are in the file idexx_all.csv. The columns include the following:
- Sample ID: Unique sample identifier for water collection laboratory analysis.
- Datetime: Date and time stamp of when the water sample was collected in Eastern Standard Time (EST).
- Date: Date stamp of when the water sample was collected in EST.
- Time: Time stamp of when the water sample was collected in EST.
- Month: Month of when the water sample was collected in EST.
- Location: Original names of sample locations or QAQC samples.
- Sample Type: Identifier for the campaign corresponding to the sample (i.e., Daily, King Tide, Street). No QAQC samples are in this dataset.
- MPN: Bacteria concentration in Most Probable Number per 100 mL of sample.
- Tidal Period: Whether the sample occurred during non-perigean spring tide conditions (Baseline) or during perigean spring tide conditions (King Tide).
- Paired: Identifier of laboratory duplicates.
Rainfall data: Rainfall data includes daily (rain_daily.csv) and hourly (rain_hourly.csv) rainfall totals obtained from the Michael J Smith Airport weather station located approximately a mile north of Front Street in Beaufort, NC (North Carolina State Climate Office, station ID: KMRH). Calculations of derived variables (rainfall totals of 3, 6, 12, 24, 36, 48, and 72 hours prior to sample collection) are outlined in the R Markdown file.
Tidal water level data: Tidal data includes water levels obtained from the NOAA Tides and Currents Station ID: 8656483, located in Beaufort, NC. The data were downloaded by month (CO-OPS_8656483_lst_mhhwft_2206.csv, CO-OPS_8656483_lst_mhhwft_2207.csv, CO-OPS_8656483_lst_mhhwft_2208.csv) and in feet. The files include predicted water levels (predicted by NOAA based on tide variation) and verified water levels (observations by NOAA). Processing of the data included compiling the monthly data into one data frame and converting the units to meters. Calculations of derived variables (tidal height, time since last high tide, and height of last high tide) are outlined in the R Markdown file.
Inputs for the pipe network model: The pipe network model was created and run using the package bathtub (described in: Gold, A.C., Brown, C.M., Thompson, S.P., Piehler, M.F., 2022. Inundation of Stormwater Infrastructure Is Common and Increases Risk of Flooding in Coastal Urban Areas Along the US Atlantic Coast. Earth’s Future, 10(3): e2021EF002139). Data needed to run the model includes shapefiles of the pipe network and elevation rasters of the site location. The pipe shapefile is bft_storm_lines_subset.shp. The structure shapefiles are pipe_ends.shp, junction_boxes.shp, drop_inlets.shp, and catch_basins.shp. The DEMs are NC_NAVD_MHHW.tif and DEMs/NOAA_CONED_DEM.tif. The coordinate system for all spatial data is NAD83(2011) / North Carolina (ftUS).
Sharing/Access information
Links to other publicly accessible locations of the data:
- Rainfall: North Carolina State Climate Office, https://climate.ncsu.edu/
- Tidal water levels: https://tidesandcurrents.noaa.gov/
Code/Software
Code for reproducing all analyses presented in the Carr et al. (2024), GeoHealth, article are included in supplement_manuscript_code.Rmd. All code was prepared in R. The code makes use of the following packages:
For data wrangling and statistical analysis:
- tidyverse
- lubridate
- janitor
- VulnToolkit
- robustlmm
- performance
- parameters
For the pipe network model:
- bathtub
- sf
- fasterize
- raster