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Flood Risk Management

Flood Risk Management. Plan Formulation, Project Development, & Stakeholder Issues. Flood Risk Management Measures. Structural measures Modify flood behavior Dams and reservoirs, levees, walls, diversion channels, bridge modifications, channel alterations, pumping, and land treatment

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Flood Risk Management

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  1. Flood Risk Management Plan Formulation, Project Development, & Stakeholder Issues

  2. Flood Risk Management Measures • Structural measures • Modify flood behavior • Dams and reservoirs, levees, walls, diversion channels, bridge modifications, channel alterations, pumping, and land treatment • Nonstructural measures • Modify damage susceptibility • Flood warning and preparedness; Evacuation and relocation; National Flood Insurance Program (NFIP); Flood proofing

  3. Dams Reservoirs Floodwalls Levees Channels Straightening Clearing and snagging Closure structures Bridge modifications Conveyance modifications Pumping Channel diversions Beach Nourishment Structural FRM Measures

  4. Structural - Reservoirs Mt. Morris Dam McCook, Ill. Yatesville Lake, Ky. Center Hill Lake, Tenn.

  5. Structural - Walls & Levees Lock Haven, PA Frankfort, KY Frankfort, KY West Columbus

  6. Channel Modification Projects Minnesota River, MN, diversion Martins Fork, KY, diversion Harlan, KY, tunnels River Rouge, MI, channelization

  7. Beach Nourishment, (Before) Miami/Dade County, FL Beach Nourishment, (After) Miami/Dade County, FL

  8. US Army Corps of Engineers Flood Proofing NATIONAL FLOOD PROOFING COMMITTEE National Nonstructural/ Flood Proofing Committee http://www.usace.army.mil/inet/functions/cw/cecwp/NFPC/nfpc.htm

  9. Nonstructural FRM Measures • Elevation • Relocation • Floodwalls, Levees and Berms • Buyout/Acquisition • Dry Flood Proofing • Wet Flood Proofing • Flooding Warning/Preparedness

  10. Elevating on Extended Foundation Walls

  11. Elevating on Fill

  12. Elevation on Piers, Posts, Piles, or Columns Piers Posts Columns Piles

  13. Relocation Process Moving the Structure • Evacuate temporary roadway • Attach structure to trailer • Transport structure to new site

  14. Relocation ProcessRestoration of Old Site • Plan must include a new use for the evacuated floodplain • Demolish and remove foundation and pavement • Disconnect and remove all utilities • Grading and site stabilization

  15. Evacuated floodplain area

  16. Ring wall/levee

  17. Ring wall/levee - closure

  18. Ring wall/levee

  19. Dry Flood Proofing: Methods Waterproof Sealant

  20. Dry Flood Proofing Method: Waterproof Sealant

  21. Wet Flood Proofing Elevate Utilities

  22. Wet Flood Proofing Let Water In Louvre

  23. Flood Warning/Preparedness Components • Flood Threat Recognition System • Warning Dissemination • Emergency Response • Post-Flood Recovery • Continued Plan Management

  24. Nonstructural FDR Solutions Flood Warning & Emergency Evacuation Plans (FWEEP) - Detailed evacuation plans and inundation mapping - Stream gages with/without remote sensing - Rain gages with remote sensing FWEEP’s are almost always cost effective and relatively inexpensive

  25. National Flood Insurance Program 44CFR 59-78 • Flood Plain Regulation (FDR) • Flood Insurance (Risk Sharing) • Flood Mitigation (FDR)

  26. FLOOD FRINGE FLOODWAY FLOOD FRINGE FEMA Definition: 100 Year Floodplain ______________________________100 year flood _____ Base Flood STREAM CHANNEL

  27. Structural measures keep the floods away from resources in the floodplain Nonstructural measures keep the resources away from floods in the floodplain Structural and Nonstructural Measures

  28. Basic Formulation Strategy • The basic formulation strategy is to formulate to meet each of your planning objectives without violating any constraints. • Every iteration of the formulation step must employ this basic strategy.

  29. How - Formulation Strategies • All possible combinations • Measures strategy • Convergent thinking • Divergent thinking

  30. Formulation Strategies • Nonstructural (statutory requirement) • Change timing • Flood • Resources • Change magnitude • Flood • Resources • Outputs • Maximum damage reduction • Life cycle costs • Sponsor financial capability • Locally Preferred (LPP) • Change location • Flood • Resources

  31. Nonstructural Opportunities New Uses of the Evacuated Flood Plain Ecosystem Restoration Recreation Spillover Benefits Water Quality Improvement E.O. 11988 NFIP Regulations Mitigation of Adverse Effects of Structural Projects

  32. How do we help this situation? High ground behind red line Town limits

  33. What measures would help? Detention pond? Channel Modification? Non-Structural Measures? High ground behind red line Town limits Levee/Wall?

  34. Evaluation of Existing

  35. Future Without Conditions

  36. Channel Modification

  37. Reservoir / Detention Storage

  38. Non-Structural Measures

  39. Levee

  40. Mathematical models are used to evaluate the impacts of alternatives for flood damage reduction The Corps’ Flood Damage Assessment (FDA) model of expected annual damage estimation is the preferred method of modeling the effects of formulated plans Developed and Maintained at HEC – Specific training is available on the FDA model FDA Model Evaluates Measures

  41. Formulation With FDA Model Channels Clearing & snagging Walls, levees Floodproofing Dams Detention reservoirs

  42. EAD Calculation for with project condition

  43. Where do we begin in formulation? Detention pond? Channel Modification? Non-Structural Measures? High ground behind red line Town limits Levee/Wall?

  44. First or Last? Detention pond High ground behind red line Levee

  45. Dependencies • Flood damage reduction plans often comprise several measures • Some measures may require implementation of other measures in order to function properly: • Interior drainage measures (pump stations and/or ponding areas) with levees/floodwalls • Warning system, operations manual, or FWEEP when plans have closure structures requiring human intervention (put the sand bag in the slot, flip the switch on the gate motor power control, etc.)

  46. Combinability • Flood damage reduction plans often comprise several increments • More often flood damage reduction plans have measures that can be combined in many ways, shapes, and sizes to achieve NED

  47. Non-Structural $30M $40M $10M Pond $40M $20M -$20M Levees/Walls $60M $80M $20M Channel $100M $85M -$15M Initial Formulation (we have only just begun) Measure NED Cost NED Benefit Net NED Benefit

  48. And we look at it all again - Reformulation • First or last positioning of measures • Dependencies • Combinability • Incremental Analysis

  49. Increment Defined • An increment is any part of a plan that can be eliminated without jeopardizing the proper function of the remaining parts of the plan. • Thus, different levels of project performance are not increments. • WRDA 1986 Definition of Separable Element. “For purposes of this Act, the term "separable element" means a portion of a project-- (1) which is physically separable from other portions of the project; and (2) which-- (A) achieves hydrologic effects, or (B) produces physical or economic benefits, which are separately identifiable from those produced by other portions of the project.”

  50. Another Example - What’s An Increment? Levee alignment Reach 1 Levee tie-back options Reach 2 High ground behind red line Town limits Reach 3

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