1. Beargrass Creek Case Study Description of the Study Area Hydrology & Hydraulics Economic Analysis Project Planning Assessment of the Risk Based Analysis Methodology

2. Beargrass Creek Study Area North Fork Middle Fork South Fork Buechel Br Ohio River 61 mi 2 Drainage Area

3. Levee on the Ohio River

4. Pump Station at the Levee (Capacity 7800 cfs!)

5. Concrete-Lined Channel

6. Detention Pond Inlet Weir

7. Beargrass Creek at the Detention Pond Pond Outlet Pipe

8. 1 2 3 4 5 6 7 8 10 11 12 13 14 15 1 2 3 4 5 Buechel Branch (2.2 miles) South Fork Beargrass Creek (12 miles) Damage Reaches 9 Example Reach SF-9

9. Beargrass Creek Case Study Description of the Study Area Hydrology & Hydraulics Economic Analysis Project Planning Assessment of the Risk Based Analysis Methodology

10. Flood Frequency Curve (SF-9) Separate curve for each reach and each plan

11. Uncertainty in Frequency Curve Reach SF-9, Without Plan Conditions ProbMean (cfs) Mean +2 SD Mean -2 SD Log 10 (SD) 0.014310300861760.0781 0.51220109813560.0229

12. 1 2 3 4 5 6 7 8 10 11 12 13 14 15 1 2 3 4 5 Buechel Branch (61 cross-sects) South Fork Beargrass Creek (202 cross-sects) Water Surface Profiles 9

14. Uncertainty in Stage-Discharge SD= 0.5 ft at 100 yr flow Constant Reduces prop. to depth

15. Beargrass Creek Case Study Description of the Study Area Hydrology & Hydraulics Economic Analysis Project Planning Assessment of the Risk Based Analysis Methodology

16. Computation of Expected Annual Damage (EAD) Stage (H) Discharge (Q) Exceedance Probability (p) Discharge (Q) Stage (H) Damage (D) Exceedance Probability (p) Damage (D)

17. Damage Categories Single-family residential Multi-family residential Commercial buildings Public buildings Automobiles Cemeteries Traffic disruption Utilities

18. p=0.999 p=0.1 p=0.01 p=0.002 Structures

19. Index Location Each damage reach has an index location All structures are assumed to exist there First floor elevation adjusted to reflect the change in location within the reach Rm 9.960 Rm 10.363 Rm 10.124 Index for SF-9 Invert p=0.01 p=0.1 p=0.5

20. Building Damage Value of the structure, V Value of the contents, C = kV k=V/C, contents to value ratio (~40%) Damage is a function of depth of flooding, expressed as ratio,r(h), of value First Floor Elevation h Depth, hr 1 (h)r 2 (h) 3ft27%35% 6ft40%45%

21. Uncertainty in Building Damage Value of structure, –SD=10% of V for residential –Commercial distribution described by Value of contents (SD of k in C=kV) Uncertainty in first floor elevation, SD=0.2ft Uncertainty in damage ratios, r(h) First Floor Elevation h

22. Stage-Damage Curve Multi-family Residential, Reach SF-9

23. Stage-Damage Curves Each structure is treated individually Stage-damage curve with uncertainty is produced for each damage category for each reach Added together to give the total stage- damage curve for the reach(?)

24. Beargrass Creek Case Study Description of the Study Area Hydrology & Hydraulics Economic Analysis Project Planning Assessment of the Risk Based Analysis Methodology

25. Planning Team Three key people: –Planner: formulates project alternatives, works with local sponsor –Hydraulic Engineer: determines discharge and stage data –Economist: estimates damage, costs, benefits and does the risk analysis

26. Planning Methodology Identify potential project components (detention ponds, levees, …) –22 initially proposed, 11 on Beargrass Creek, and 11 on Buechel Branch Evaluate them all individually to see if net benefits are positive –8 components on Buechel Branch eliminated Combine components into plans, incrementally –10 components in NED plan: 8 detention ponds, 1 floodwall, 1 channel improvement

27. 1 2 3 4 5 6 7 8 10 11 12 13 14 15 1 2 3 4 5 Buechel Branch Three Plan Development Reaches 9 3 2 1

28. Risk of Flooding Establish a target stage at each damage reach index point Find annual probability of exceeding that stage Find reliability of passing design floods Target Stage

29. Assessment of Engineering Risk Conditional probability –Assumes a particular flood severity Annual probability –Integrates over all flood severities Risk measures actually used –Annual exceedance probability –Conditional nonexceedance probability Target Stage H F(h) 0 1 Nonexceedance probability Exceedance probability

30. Computation of Engineering Risk Measures from the Stage-Frequency Curve Annual exceedance probability –Find p e for target stage at each Monte Carlo replicate –Get expected value and median of p e values over all simulations –Get long term risk as 1-(1-p e ) n Conditional nonexceedance probability –Find H* for given p* at each replicate –Find % of replicates for which H* < Target stage Q Q* f 2 (H|Q) H* p f 1 (Q|p) p* Q* H p f 3 (H|p) p* H* H pepe Target Stage Q

32. Beargrass Creek Case Study Description of the Study Area Hydrology & Hydraulics Economic Analysis Project Planning Assessment of the Risk Based Analysis Methodology

33. Overall Assessment The core methodology is solid and is an advance in engineering practice of flood risk assessment Focus is completely on damage reaches considered as statistically independent entities Whole project risk and 25%,50%,75% damage values cannot be built up this way Can specification of standard deviations of analysis variables be improved?

34. Beargrass Creek 100 year Flood Plain Map Middle Fork South Fork

35. Spatial Subdivision of the Region Spatial UnitUsed for Whole River Expected Annual Damage (EAD), Benefit-Cost analysis 3 Main River ReachesIncremental analysis to get NED plan 22 Damage Reaches Basic unit for analysis using HEC-FDA 263 Hydraulic Cross- sections Water surface elevation profile computation 2150 Structures Structure inventory

36. Whole Project Risk Assessment Take a flood of severity, p, and integrate the damage along the reach –Without any plan (o) –With a plan (w) –Benefit of plan is B = D o - D w Randomize the flood discharge and stage for the whole project rather than for each reach Compute project-based damage values for each randomization and use them to get B 25, B 75 values