PatapscoBack River SWMM Model

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Patapsco/Back River SWMM Model

• Part I - Hydrology
• Maryland Department of the Environment

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Patapsco/Back River Watershed
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Storm Water Management ModelSWMM

• Selection Criteria
• Primarily Urban Runoff Model (wet weather flow)
• Existing studies available
• Existing parameterization information available
• Multiple Buildup/Washoff Functions
• Limited parameters
• Stakeholder involvement
• Credibility (EPA)

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SWMM Blocks

• Rainfall
• Hourly
• Runoff
• Urban/Non-Urban
• Infiltration (Horton)
• Buildup/Wash off
• USLE

• Transport
• Point Source
• Baseflow
• Postprocessing
• Temporal Load
• Event Mean Concentration

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Hydrology Calibration Methodology

• Parameterization
• Linked to topographic/physiographic information
• Physically based
• Flow Comparison
• Daily Cumulative
• Daily Frequency
• Monthly
• Seasonal
• Annual
• Analysis
• Statistical Error
• Correlation

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Land use

• Maryland Office of Planning (1997)
• Farm Services Agency and
• Agricultural Census Data

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Land Use Aggregation
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SWMM/HSPF Model Segmentation
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Soils

• Soil Data Sources
• BCI SSURGO
• BCO - County GIS
• AA Ragan
• Carroll Ragan
• Howard - Ragan

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Channel X-Section

• Jones Falls
• Overbank extracted
• from DEM
• Main Section From Surveyed Channel Info

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X-Section Editing for SWMM
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Precipitation

• Stations (2)
• Advantages
• Quality of Data
• Reduces averaging of rainfall intensity
• Disadvantages
• Minimal spatial variability of rainfall
• Edits for year 2001

• Meteorological data obtained from CBP Watershed
  Model (Region V)

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SWMM Baseflow Methodology

• 10 USGS Gauges for Analysis
• (1/1/92 9/30/01)
• Complete Time Series (5 Gauges)
• Partial Time Series (5 Gauges)
• 1992 1996 (regression)
• 1996 2001
• Baseflow Separation
• (USGS HYDSEP)
• Normalize Baseflow by Area

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SWMM Wet Weather Flow Comparison
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USGS Calibration Stations

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Patapsco/Back River Hydrology Calibration

• Jones Falls (HSPF / SWMM)
• Gwynns Falls (HSPF / SWMM)
• Patapsco River (HSPF / SWMM / CBP)
• Back River (SWMM)

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Jones Falls Hydrology Calibration
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Gwynns Falls Hydrology Calibration
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Patapsco River Hydrology Calibration
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Back River Hydrology Calibration
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Hydrology Calibration Monthly Statistical Summary
Simulation End Date 12/31/98
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Hydrology Calibration Annual Statistical Summary
Simulation End Date 12/31/98
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HSPF/SWMM Calibration Summary Conclusions

• Reasonable error and correlation with gauge data
• Models support overall trends of monthly, season
  and annual flows