1. Art of Calibration in the Science of H&H Modeling Amit Sachan, PE, CFM, Project Manager/ Water Resource Engineer Robert Billings, PE, PH, CFM Project Manager, Mecklenburg County

2. Agenda Definitions Definitions Case Study Case Study Lessons Learned Lessons Learned Summary Summary Definitions Definitions Case Study Case Study Lessons Learned Lessons Learned Summary Summary

3. Modeling Modeling Representation of a process/object Representation of a process/object Calibration Calibration Models: Adjustment of the parameters of a mathematical or numerical model in order to optimize the agreement between observed data and the model's predictions (source: Wikipedia) Models: Adjustment of the parameters of a mathematical or numerical model in order to optimize the agreement between observed data and the model's predictions (source: Wikipedia) Tools: Checking or adjusting (by comparison with a standard) the accuracy of a measuring instrument (source: TheFreeDictionary.com) Tools: Checking or adjusting (by comparison with a standard) the accuracy of a measuring instrument (source: TheFreeDictionary.com) Consistent and systematic Consistent and systematic Modeling Modeling Representation of a process/object Representation of a process/object Calibration Calibration Models: Adjustment of the parameters of a mathematical or numerical model in order to optimize the agreement between observed data and the model's predictions (source: Wikipedia) Models: Adjustment of the parameters of a mathematical or numerical model in order to optimize the agreement between observed data and the model's predictions (source: Wikipedia) Tools: Checking or adjusting (by comparison with a standard) the accuracy of a measuring instrument (source: TheFreeDictionary.com) Tools: Checking or adjusting (by comparison with a standard) the accuracy of a measuring instrument (source: TheFreeDictionary.com) Consistent and systematic Consistent and systematic Definitions

4. Calibration Calibration Setting for known values Setting for known values Accuracy vs. Precision Accuracy vs. Precision For Physical models For Physical models Multiple parameters Multiple parameters Multiple values Multiple values Classical Calibration for the Models Classical Calibration for the Models Sensitivity Analysis Sensitivity Analysis Calibration Calibration Validation Validation Calibration Calibration Setting for known values Setting for known values Accuracy vs. Precision Accuracy vs. Precision For Physical models For Physical models Multiple parameters Multiple parameters Multiple values Multiple values Classical Calibration for the Models Classical Calibration for the Models Sensitivity Analysis Sensitivity Analysis Calibration Calibration Validation Validation Definitions Source: MedicalScale

5. Southern NC at the NC-SC Border Southern NC at the NC-SC Border 330 miles of FEMA streams 330 miles of FEMA streams State-of-the-art Flood warning system State-of-the-art Flood warning system 50 stream gages within LSCBC 50 stream gages within LSCBC Case Study

6. Cavalier Apartments Model accuracy & precision directly Impact public $s due to highly urban area

7. Storm Selection Storm Selection High-end Storm (~100 Yr) High-end Storm (~100 Yr) August 2008 August 2008 Low-end Storms (~2 Yr) Low-end Storms (~2 Yr) September 2006 September 2006 March 2007 March 2007 Storm Selection Storm Selection Continuous Data Continuous Data Low Variability Low Variability Homogenous Response Homogenous Response Storm Selection Storm Selection High-end Storm (~100 Yr) High-end Storm (~100 Yr) August 2008 August 2008 Low-end Storms (~2 Yr) Low-end Storms (~2 Yr) September 2006 September 2006 March 2007 March 2007 Storm Selection Storm Selection Continuous Data Continuous Data Low Variability Low Variability Homogenous Response Homogenous Response Rainfall Distribution during August 25-27, 2008 (Source: USGS) Case Study – Hydrologic Calibration

9. a. Sensitivity Analysis Routing Techniques Routing Techniques Modified Puls Modified Puls Mushkingham Cunge Mushkingham Cunge Level Pool Routing Level Pool Routing Lag time Lag time Curve Numbers Curve Numbers AMC Conditions AMC Conditions Initial Abstraction Initial Abstraction a. Sensitivity Analysis Routing Techniques Routing Techniques Modified Puls Modified Puls Mushkingham Cunge Mushkingham Cunge Level Pool Routing Level Pool Routing Lag time Lag time Curve Numbers Curve Numbers AMC Conditions AMC Conditions Initial Abstraction Initial Abstraction Case Study – Hydrologic Calibration

10. Case Study- Hydrologic Calibration Additional Storage Areas

11. Case Study- Hydrologic Calibration Change & Effect Matrix

12. b. Calibration Alternatives & Iterations 14 scenarios 14 scenarios Gage weighting Gage weighting Equal Weighting Equal Weighting AMC conditions AMC conditions Initial Abstraction Initial Abstraction Aug 2008 Event Aug 2008 Event Initial Abstraction Initial Abstraction Lag Time Lag Time b. Calibration Alternatives & Iterations 14 scenarios 14 scenarios Gage weighting Gage weighting Equal Weighting Equal Weighting AMC conditions AMC conditions Initial Abstraction Initial Abstraction Aug 2008 Event Aug 2008 Event Initial Abstraction Initial Abstraction Lag Time Lag Time Case Study – Hydrologic Calibration

13. Case Study- Hydrologic Calibration Observations Observations Time to Peak - matches Time to Peak - matches Peak Discharges – within reasonable limits Peak Discharges – within reasonable limits Volume – within reasonable limits Volume – within reasonable limits Observations Observations Time to Peak - matches Time to Peak - matches Peak Discharges – within reasonable limits Peak Discharges – within reasonable limits Volume – within reasonable limits Volume – within reasonable limits

14. Calibration – Inter relationship Airplane example Airplane example Source: Wikipedia

15. Calibration – Inter relationship Relationship between Hydrologic & Hydraulic Models Relationship between Hydrologic & Hydraulic Models Hydrologic Model Hydraulic Model

16. Case Study- Hydraulic Calibration High Water Marks High Water Marks Little Sugar Creek Little Sugar Creek Little Hope Creek Little Hope Creek Briar Creek Briar Creek High Water Marks High Water Marks Little Sugar Creek Little Sugar Creek Little Hope Creek Little Hope Creek Briar Creek Briar Creek

17. Case Study- Hydraulic Calibration High Water Marks High Water Marks Match within 0.5 ft Match within 0.5 ft Quality Quality Parameter Changes Parameter Changes Mannings n Mannings n Ineffective Areas Ineffective Areas Cont/Exp Coeff Cont/Exp Coeff High Water Marks High Water Marks Match within 0.5 ft Match within 0.5 ft Quality Quality Parameter Changes Parameter Changes Mannings n Mannings n Ineffective Areas Ineffective Areas Cont/Exp Coeff Cont/Exp Coeff

18. Case Study- Hydraulic Calibration c. Validation Hydrologic Hydrologic Hydraulic Hydraulic c. Validation Hydrologic Hydrologic Hydraulic Hydraulic

19. Case Study- Hydraulic Calibration …and iterations continue until reasonable matches in hydrologic AND hydraulic models Hydrologic Model Hydraulic Model

20. Lessons Learned Analysis (Science Component) Analysis (Science Component) Based on available data Based on available data Based on required detail Based on required detail Sensitivity Analysis Sensitivity Analysis Time/Budget Available Time/Budget Available Trade offs (Art Component) Trade offs (Art Component) Not exact matches Not exact matches Engineering Judgment Engineering Judgment Analysis (Science Component) Analysis (Science Component) Based on available data Based on available data Based on required detail Based on required detail Sensitivity Analysis Sensitivity Analysis Time/Budget Available Time/Budget Available Trade offs (Art Component) Trade offs (Art Component) Not exact matches Not exact matches Engineering Judgment Engineering Judgment

21. QUESTIONS ?? Thank you