Model Calibration in MarylandJune Model Calibration in Maryland June 12, 2015

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

Model Calibration in MarylandJune 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

Model Calibration in MarylandJune 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.

Model Calibration in MarylandJune 20155

Model Calibration in MarylandJune 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

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

Model Calibration in MarylandJune 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)

Model Calibration in MarylandJune 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

Model Calibration in MarylandJune 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

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

Model Calibration in MarylandJune

Model Calibration in MarylandJune 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

Model Calibration in MarylandJune 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

Model Calibration in MarylandJune 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

Model Calibration in MarylandJune 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.

Model Calibration in MarylandJune 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-year year year year8.23

Model Calibration in MarylandJune Initial Results Years Regression Equation (cfs)Upper Bounds (cfs) Win-TR20 (cfs)

Model Calibration in MarylandJune Calibration Window

Model Calibration in MarylandJune Next Step Modify Tc 2.0Modify Tc 2.0 Modify CN 80Modify CN 80

Model Calibration in MarylandJune Results Years Regression Equation (cfs)Upper Bounds (cfs) Win-TR20 (cfs)

Model Calibration in MarylandJune Calibration Window

Model Calibration in MarylandJune The End

Model Calibration in MarylandJune Porcupine Mountain State Park, Michigan

Model Calibration in MarylandJune