Assessing potential effects of highway runoff on receiving-water quality at selected sites in Oregon with the Stochastic Empirical Loading and Dilution Model (SELDM)

Abstract

Map showing Murder Creek at Interstate 5 (Pacific Highway), near Albany, Oregon ...15 9. Map showing Wall Creek at Interstate 5 (Pacific Highway), near Ashland, Oregon ......16 10. Graphs showing the stochastic populations of dilution factors for highway runoff or best management practices (BMP) discharge showing the effect of BMP treatments and upstream flow assumptions on the simulated dilution factors for Tryon Creek at Interstate 5

Assessing water quality from highway runoff at selected sites in North Carolina with the Stochastic Empirical Loading and Dilution Model (SELDM)

“…SELDM uses precipitation statistics to stochastically simulate the number, volume, and duration of runoffgenerating events and the time between events. Storm-event precipitation statistics define the characteristics of each storm event and the number of events in the simulation (Risley and Granato, 2014). SELDM uses the EPA definition of a runoff-generating event, which is based on hourly precipitation values, a minimum precipitation volume of 0.1 inch (in.…”

“…For example, sediment concentrations on the order of magnitude of 1,000,000 milligrams per liter (mg/L) occur in the southwestern United States but would not be expected to occur in North Carolina (in the absence of wildfires, landslides, or improperly managed development). Risley and Granato (2014) discussed possibilities for generating extreme values and noted that although there are solubility limits for purely dissolved constituents carried within sediment-laden streamflows, concentrations of whole water (total) constituents are not so limited because concentrations associated with the sediment phase of a whole water sample can be large.…”

“…Simulations using the North Carolina-enhanced SELDM are described to demonstrate methods for providing risk-based information about potential effects of stormwater runoff on downstream water quality and the potential for mitigating those risks by using BMPs. Risley and Granato (2014) demonstrated example SELDM applications at six highway sites in Oregon, with highway catchment areas ranging from 3.85 to 11.83 acres and upstream-basin drainage areas ranging from 0.16 to 6.56 mi 2 . These example simulations provided information about potential effects of runoff at specific sites, but the lessons learned may not be transferable to other basins in the State.…”

“…The U.S. Geological Survey (USGS) in cooperation with the Federal Highway Administration (FHWA) developed the Stochastic Empirical Loading and Dilution Model (SELDM) to provide the tools and techniques necessary for simulating the effects of stormwater runoff on downstream water quality (Granato, 2013;Risley and Granato, 2014). SELDM uses Monte Carlo methods to generate a stochastic (randomly determined) population of the concentrations, flows, and loads of stormwater constituents needed to implement a mass-balance model for the site of interest, often a highway catchment, and the basin upstream from the stormwater outfall to assess the risk for adverse effects of runoff.…”

Estimating Risks for Water-Quality Exceedances of Total-Copper from Highway and Urban Runoff under Predevelopment and Current Conditions with the Stochastic Empirical Loading and Dilution Model (SELDM)

“…The average of 71 total-hardness concentrations measured in the Charles River at Dover (USGS station 01103500) was about 37.4 milligrams per liter (mg/L). Total-hardness concentrations tend to decrease with increasing streamflow (Granato and others, 2009;Risley and Granato, 2014), so a water-quality transport curve was developed to model total-hardness concentrations in stormflow. A water-quality transport curve is a relation between stormflow volumes and constituent concentrations (Granato, 2006;2013a, Granato andothers, 2009).…”