Assessing Water Quality from Highway Runoff at Selected Sites in North Carolina with the Stochastic Empirical Loading and Dilution Model (SELDM)
Dates
Publication Date
2019-05-15
Time Period
1900
Time Period
2015
Citation
Weaver, J.C., Granato, G.E., and Fitzgerald, S.A., 2019, Assessing water quality from highway runoff at selected sites in North Carolina with the Stochastic Empirical Loading and Dilution Model (SELDM): U.S. Geological Survey data release, https://doi.org/10.5066/F7V69HV8.
Summary
In 2013, the U.S. Geological Survey (USGS) in partnership with the U.S. Federal Highway Administration (FHWA) published a new national stormwater quality model called the Stochastic Empirical Loading Dilution Model (SELDM). The model is optimized for roadway projects but in theory can be applied to a broad range of development types. SELDM is a statistically-based empirical model pre-populated with much of the data required to run the application successfully. The model uses Monte Carlo methods as opposed to deterministic methods to generate a wide range of possible discharge and precipitation inputs from the upstream basin and highway site. SELDM is particularly useful for stormwater managers in its ability to provide the statistical [...]
Summary
In 2013, the U.S. Geological Survey (USGS) in partnership with the U.S. Federal Highway Administration (FHWA) published a new national stormwater quality model called the Stochastic Empirical Loading Dilution Model (SELDM). The model is optimized for roadway projects but in theory can be applied to a broad range of development types. SELDM is a statistically-based empirical model pre-populated with much of the data required to run the application successfully. The model uses Monte Carlo methods as opposed to deterministic methods to generate a wide range of possible discharge and precipitation inputs from the upstream basin and highway site. SELDM is particularly useful for stormwater managers in its ability to provide the statistical probability of a water-quality standard exceedance downstream of a stormwater discharge location over the course of a long period of record. SELDM supports a variety of best management practices (BMPs), which the user can apply to the stormwater discharge and evaluate the subsequent instream water-quality benefit. This functionality makes the model well suited for supporting BMP-specific cost/benefit analyses.
In 2015, the North Carolina Department of Transportation (NCDOT) initiated a partnership with USGS to enhance the national SELDM model with additional NC-specific data to improve the model’s predictive performance across the State. Specific USGS data incorporated into the NC-enhanced SELDM model included selected North Carolina streamflow data as well as water-quality transport curves for selected constituents. Streamflow statistics (based on data through the 2015 water year) were computed for 266 selected continuous-record streamgages and updated in the StreamStatsDB, which is accessible to users from the USGS StreamStats application for North Carolina. Instantaneous streamflow data available at 30 selected continuous-record streamgages across North Carolina with drainage areas ranging from 4.12 to 63.3 square miles were used to develop site-specific recession ratio statistics at these sites. Using data through the 2016 water year, water-quality transport curves were developed for 27 streamgages for the following constituents: suspended sediment concentration, total nitrogen, total phosphorus, turbidity, copper, lead, and zinc.
The NCDOT identified NC highway-runoff water-quality and quantity data available from non-USGS sources (compiled by a private NCDOT contractor). These data were reviewed by USGS and – where deemed acceptable – were uploaded into the FHWA Highway-Runoff Database, the data warehouse and preprocessor for SELDM (Granato and Cazenas, 2009; Smith and Granato, 2010). Based on the analysis techniques documented by Granato (2014) in a national BMP study and using available water-quality sample data from selected highway-runoff and BMP site pairs, performance data from the NC highway-runoff research reports were analyzed and incorporated into the NC SELDM model for three BMP types.
As part of the NC SELDM study, simulations using the NC SELDM model were completed to demonstrate example impacts and evaluations of stormwater runoff on downstream water quality at six hypothetical upstream basin and highway sites across the State.
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Related External Resources
Type: Citation
Weaver, J.C., Granato, G.E., and Fitzgerald, S.A., 2019, Assessing water quality from highway runoff at selected sites in North Carolina with the Stochastic Empirical Loading and Dilution Model (SELDM): U.S. Geological Survey Scientific Investigations Report 2019–5031, 99 p., https://doi.org/10.3133/sir20195031.
Granato, G.E., 2009, Computer programs for obtaining and analyzing daily mean streamflow data from the U.S. Geological Survey National Water Information System Web Site: U.S. Geological Survey Open-File Report 2008–1362, 123 p., 5 appendixes, CD-ROM, available at https://pubs.usgs.gov/of/2008/1362/
The purpose of this USGS data release is to publish NC SELDM streamflow statistics and summary statistics of physical and chemical data in support of the information provided in the above-referenced report.
This data release consists of two data sets, "NC SELDM streamflow statistics..." and "NC SELDM summary statistics for physical and chemical data...".
The tables that are uploaded for the "NC SELDM streamflow statistics for 266 streamgages across North Carolina" sub-section are primarily the support files for the StreamStatsDB update that was completed when the report was approved. The SELDM streamflow statistics were calculated using the Get National Water Information System Streamflow (Q) (GNWISQ) and Streamflow (Q) Statistics (QSTATS) computer programs developed and described by Granato (2009, appendixces 1 and 4). This is discussed near the end of the "Prestorm streamflow statistics" section in the above-referenced report. A large table of selected site attributes and StreamStats basin characteristics that were compiled for the 266 streamgages is also provided as a part of this data release. A ReadMe file is also included in the sub-section of the data release.
The tables that are uploaded for the "NC SELDM summary statistics for physical and chemical data at NC highway-runoff and bridge-deck sites" sub-section of the data release support the statewide medians table (Table 7) discussed within the "Simulating highway-runoff quality" section in the above-referenced report. This is a .csv file for each of the 11 constituents referenced in Table 11. Descriptions of the data fields (or columns) in the .csv tables are provided at the top of each .csv file. A ReadMe file is also included in the sub-section of the data release.
