1. Model Calibration in MarylandJune 20151 Model Calibration in Maryland June 12, 2015

2. Model Calibration in MarylandJune 20152 Outline State Highway Administration Procedure State Highway Administration Procedure - Gaged watersheds - Ungaged watersheds - Example

3. Model Calibration in MarylandJune 20153 When to Calibrate Stream restoration projectStream restoration project Bridge or culvert sizingBridge or culvert sizing Setting 100-yr flood plain limits with ultimate development or any developmentSetting 100-yr flood plain limits with ultimate development or any development

4. Model Calibration in MarylandJune 20154 Calibration Issues Often overlooked for any watershed studyOften overlooked for any watershed study SHA requires that the study be within the regional peak flow and plus one standard error.SHA requires that the study be within the regional peak flow and plus one standard error.

5. Model Calibration in MarylandJune 20155

6. Model Calibration in MarylandJune 20156 SHA Publication This publication provides guidelines on which variables to adjust and the limits of adjustmentThis publication provides guidelines on which variables to adjust and the limits of adjustment

7. Model Calibration in MarylandJune 20157 Frequency - years Peak Flow - cfs 210100 X X X X WinTR-20 Results – before calibration WinTR-20 Results – after calibration Upper Limit Regression Estimate Calibration Target Range

8. Model Calibration in MarylandJune 20158 Measured Data Stream gage within the watershedStream gage within the watershed Regional regression equations of stream gage data (SHA 2010 or GISHydro 2000)Regional regression equations of stream gage data (SHA 2010 or GISHydro 2000)

9. Model Calibration in MarylandJune 20159 Stream gage data On sites that are on same stream and with plus or minus 50% of the drainage area of the gageOn sites that are on same stream and with plus or minus 50% of the drainage area of the gage There is a procedure outlined in the manual for determining the peak flow frequency curveThere is a procedure outlined in the manual for determining the peak flow frequency curve

10. Model Calibration in MarylandJune 201510 Calibration If calibration is needed, use a historic eventIf calibration is needed, use a historic event - Match hydrograph volume - Match hydrograph peak discharge (and time of peak if possible) Use to second event to verify calibrationUse to second event to verify calibration - May have to change CN in order to match hydrograph volume

11. Model Calibration in MarylandJune 201511 Guidance “User should calibrate or validate the results of a WinTR-20 run against an independent source of measured data”

12. Model Calibration in MarylandJune 201512

13. Model Calibration in MarylandJune 201513 Calibration Procedure Table 4.2 suggests in the following orderTable 4.2 suggests in the following order - Modify the Tc Modify n valuesModify n values - Change the CN - Change HSG due to urbanization - Change the reach lengths Storage at culvertsStorage at culverts - Change the Dim hydrograph - Rainfall duration

14. Model Calibration in MarylandJune 201514 Guidance Change CN by ± 10 %Change CN by ± 10 % Modify n by ± 25 % for overland flowModify n by ± 25 % for overland flow Modify n by ± 50 % for shallow concentrated and channel flowModify n by ± 50 % for shallow concentrated and channel flow Modify L by ± 25 % for shallow concentrated and channel flowModify L by ± 25 % for shallow concentrated and channel flow

15. Model Calibration in MarylandJune 201515 Guidance Cross Section Area to ± 25%Cross Section Area to ± 25% Modify n by ± 50% for x-sectionsModify n by ± 50% for x-sections Reach lengths by up to 30% for 1:24000 and up to to 19% for 1:2400 mapsReach lengths by up to 30% for 1:24000 and up to to 19% for 1:2400 maps If reach length is increased, generally the slope will decreaseIf reach length is increased, generally the slope will decrease Do not adjust ARCDo not adjust ARC

16. Model Calibration in MarylandJune 201516 Dimensionless Unit Hydrograph Use Panel recommends DMV DUH in Eastern Coastal Plain. In Western Coastal Plain decide on a case-by-case basis.Panel recommends DMV DUH in Eastern Coastal Plain. In Western Coastal Plain decide on a case-by-case basis.

17. Model Calibration in MarylandJune 201517 Example Montgomery County DA = 3.70 Square MilesDA = 3.70 Square Miles Tc = 1.8 hoursTc = 1.8 hours CN = 85CN = 85 Rainfall Distribution NOAA_C (Type NO_C in WinTR-20)Rainfall Distribution NOAA_C (Type NO_C in WinTR-20) NOAA 14 Rainfall Amount (inch) 2-year3.10 10-year4.77 50-year7.03 100-year8.23

18. Model Calibration in MarylandJune 201518 Initial Results Years Regression Equation (cfs)Upper Bounds (cfs) Win-TR20 (cfs) 279810001329 10190023002512 50323038004157 100420046005023

19. Model Calibration in MarylandJune 201519 Calibration Window

20. Model Calibration in MarylandJune 201520 Next Step Modify Tc 2.0Modify Tc 2.0 Modify CN 80Modify CN 80

21. Model Calibration in MarylandJune 201521 Results Years Regression Equation (cfs)Upper Bounds (cfs) Win-TR20 (cfs) 27981000962 10190023001993 50323038003500 100420046004313

22. Model Calibration in MarylandJune 201522 Calibration Window

23. Model Calibration in MarylandJune 201523 The End

24. Model Calibration in MarylandJune 201524 Porcupine Mountain State Park, Michigan

25. Model Calibration in MarylandJune 201525