cee5734_week13_2011

cee5734_week13_2011 - CEE 5734 Urban Hydrology and...

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Glenn E. Moglen Department of Civil & Environmental Engineering Virginia Tech Water Quality, Nutrient Loading, BMPs, and Best BMP Strategies CEE 5734 – Urban Hydrology and Stormwater Management Week 13

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Questions Logistics for remainder of semester Nutrient Loading apart from SWMM Schueler’s “Simple Method” Example: Chesapeake Bay Program BMPs: Background Example Chesapeake Bay Program BMP optimization Today’s Agenda
Also called “PLOAD” method by EPA Developed by Tom Schueler for MWCOG (1987) Document and summary supplied. Pluses: It’s “simple” It’s widely used Minuses: Maybe it’s too simple Very sensitive to assumed concentrations Avoids real-world complexities Scale? Simple Method

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Runoff coefficient based on imperviousness Simple Method / EPA PLOAD Method

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C U values… From Schueler (1987) document
Simple Method – EMC Values – “PLOAD” Document

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Other values and assumptions Assumptions to make Simple Method / PLOAD go: P = 40 inches/year (good for most of Virginia) P J = 0.9 (default) R VU : based on previous equation. Imperviousness from this TR-55 or other source C U : based on Schueler 1987 or PLOAD appendices A U : calculated from maps or by GIS using standard methods
Example: Given: 2.4 mi 2 watershed is 50% new suburban (assume 38% imp.), 20% business (assume 85% imp.), and 30% forest (assume 0% imp.). Assume annual P = 40 inches Find: Annual Nitrogen load Simple Method

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Based on previous table, we determine: *C U values from Schuler (1987) Simple Method Land Use Area (ac) Imp. (%) R vu C U * (mg/l of N) Load (lbs/year) Unit Load [lbs/(ac-yr)] Residential 1.2 38 0.392 2.0 7.7 6.4 Commercial 0.48 85 0.815 2.17 6.9 14.4 Forest 0.72 0 0.05 0.78 0.23 0.32 Sum 15 lbs/yr
Bay-wide model based on HSPF model Produces output at “segment” level based on somewhat sparse modeling data “edge” modeling “as delivered to Bay” modeling

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cee5734_week13_2011 - CEE 5734 Urban Hydrology and...

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