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The Stochastic Empirical Loading and Dilution Model (SELDM) for stormwater-quality risk analyses

SELDM, a data-driven model, calculates storm & annual loads using Monte Carlo methods. It supports NEPA process & facilitates decision-making. Estimate risks & BMP effects with long-term simulations.

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The Stochastic Empirical Loading and Dilution Model (SELDM) for stormwater-quality risk analyses

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  1. The Stochastic Empirical Loading and Dilution Model (SELDM) for stormwater-quality risk analyses By Gregory E. Granato and Susan C. Jones

  2. SELDM was tested and/or reviewed by 43 professionals from USGS, USEPA, USFWS, and 16 state agencies

  3. SELDM is the Stochastic Empirical Loading and Dilution Model • Stochastic—Uses Monte Carlo methods to create a sample of events representing combinations of flows concentrations and loads • Empirical—Based on data and statistics rather than pure theory • Loading—Provides storm and annual loads • Dilution—Mixing of upstream and highway indicates chance of exceeding a target value

  4. SELDM uses a simple mass balance approach to calculate flows, concentrations, and loads by storm and by year

  5. SELDM is designed to facilitate the NEPA process

  6. Supports the Environmental Decision-Making Process Ecoregion/ Rain Zone • First Level: Regional Inputs • Hydrologic Similarity • Ecoregions: pre-storm flow, precipitation, QW • Rain Zones: precipitation • Second Level: Nearby Sites • Hydrologic Similarity • Proximity • Third Level: User-Defined Statistics from Data Collected On Site • Expensive • Delays: one or more years of data collection Nearby Site(s) User Defined Analysis/ Analyte

  7. The HRDB provides highway-runoff flow and quality data version 1.0.0b will have 39 sites, 1,140 storms, and 25,087 EMCs from NC

  8. SELDM uses pre-loaded precipitation, upstream flow, and water-quality data. Values can be selected by region or by proximity to your site of interest

  9. The drainage area, basin length, and mean basin slope are physiographic basin properties

  10. The total impervious area (TIA), which is the fraction or percentage of anthropogenic impervious surfaces in a basin, is the primary anthropogenic basin property

  11. SELDM uses a “Black Box” approach to model flow reduction, hydrograph extension and concentration reduction from BMP(s)

  12. SELDM has a GUI with a series of forms Documentation Analyst Project Analysis Site and Region Highway Grid Ecoregion Upstream Basin Hydrology Rv Streamflow Precipitation Lake Basin Water Quality Highway Upstream Downstream BMP Run Analysis

  13. Long-term simulations are used to estimate risks of exceeding concentrations by using available data

  14. Long term simulationas also indicate the effect of BMPs on the risk for water-quality exceedances in discharges

  15. Simulating upstream stormflow, highway runoff, and BMP discharge indicates the downstream effects

  16. SELDM can be used to estimate annual loads with and without BMPs for a site or by acre

  17. The web site has links to reports, software, and SELDM version 1.0.2 at https://doi.org/10.5066/F7BG2M33

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