1. Patapsco/Back River SWMM Model Part I - Hydrology Maryland Department of the Environment

2. Patapsco/Back River Watershed

3. Storm Water Management Model SWMM 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)

4. SWMM Blocks Rainfall –Hourly Runoff –Urban/Non-Urban –Infiltration (Horton) –Buildup/Wash off –USLE Transport –Point Source –Baseflow Postprocessing –Temporal Load –Event Mean Concentration

5. Hydrology Calibration Methodology Parameterization –Linked to topographic/physiographic information –Physically based Flow Comparison –Daily Cumulative –Daily Frequency –Monthly –Seasonal –Annual Analysis –Statistical Error –Correlation

6. Land use Maryland Office of Planning (1997) Farm Services Agency and Agricultural Census Data

7. Land Use Aggregation

8. SWMM/HSPF Model Segmentation

9. Soils Soil Data Sources –BCI – SSURGO –BCO - County GIS –AA – Ragan –Carroll – Ragan –Howard - Ragan

10. Channel X-Section Jones Falls Overbank extracted from DEM Main Section From Surveyed Channel Info

11. X-Section Editing for SWMM

12. 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)

13. 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

14. SWMM Wet Weather Flow Comparison

15. USGS Calibration Stations

16. Patapsco/Back River Hydrology Calibration Jones Falls (HSPF / SWMM) Gwynns Falls (HSPF / SWMM) Patapsco River (HSPF / SWMM / CBP) Back River (SWMM)

17. Jones Falls Hydrology Calibration

24. Gwynns Falls Hydrology Calibration

25. Patapsco River Hydrology Calibration

30. Back River Hydrology Calibration

35. Hydrology Calibration Monthly Statistical Summary * Simulation End Date 12/31/98

36. Hydrology Calibration Annual Statistical Summary * Simulation End Date 12/31/98

37. HSPF/SWMM Calibration Summary & Conclusions Reasonable error and correlation with gauge data Models support overall trends of monthly, season and annual flows