Comprehensive Flood Mitigation for 12,000 Properties

Transcription

1 Comprehensive Flood Mitigation for 12,000 Properties Lori Rafferty, PE, CFM, Louisville MSD & Louie Greenwell, GISP, CFM, T&M Associates Association of State Floodplain Managers 2014 State Conference June 4, 2015

2 PRESENTATION OUTLINE Project background Methodology Document previous mitigation Develop floodprone inventory Risk evaluation Develop mitigation alternatives Community Rating System benefits Next steps

3 PROJECT BACKGROUND Louisville, KY is a river town Significant history of flooding

4 PROJECT BACKGROUND Approximately 15% of Louisville/Jefferson County is in the floodplain 12,000 floodprone properties 44 SRL Properties 278 RL Properties

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6 HISTORICAL FLOODING ,000 people evacuated Ohio River crested about 40 above normal pool

7 HISTORICAL FLOODING Floodwall and Levee System 28.9 miles long Protects approximately 80,000 properties 16 flood pump stations

8 HISTORICAL FLOODING 1997 Up to 12.5 inches in 2 days Ohio River crested 26 above normal pool

9 HISTORICAL FLOODING September 2006: Up to 10 in 24 hrs

10 HISTORICAL FLOODING August 2009: Up to 8 in 75 minutes

11 HISTORICAL FLOODING October 2013 Up to 7 in 24 hrs

12 HISTORICAL FLOODING March 2015 Ohio River flooding

13 HISTORICAL FLOODING April in 24 hours

14 PREVIOUS BUYOUTS

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16 PROJECT JUSTIFICATION Widespread flooding issues Reactive mitigation projects Needed a Comprehensive Mitigation Plan Fair and balanced Easy to communicate Transparent Include floodprone Combined Sewer Area

17 PROJECT SCOPE Develop a plan to address countywide flooding issues for approximately 12,000 flood prone structures Project Task / Activities Task 1: Document Prior Mitigation Activities Task 2: Grant Administration & Support Task 3: Grant Development Task 4: Countywide Mitigation Inventory Task 5: Risk Evaluation Task 6: Define Mitigation Options/Actions Task 7: Compile List of Alternative Funding Sources Task 8: Develop Countywide Report & Presentation Task 9: Coordination with MSD CRS Team Task 10: October 2013 Mitigation Support

18 PRIOR MITIGATION PROJECTS Almost 700 completed projects identified Used multiple source documents Prior Grant submissions Board Presentations 50 year history of MSD and other historical documents Review of plans in eb Each classified by type of mitigation (e.g., acquisition, elevation, basin, floodwall/levee, floodproofing) Designated as flood control or local drainage improvement Identified the project year and cost/funding where available

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23 COUNTYWIDE MITIGATION PRIORITIZATION Identify Flood Prone Structures Data collection from multiple sources Property value info from County PVA Ground elevation data from LOJIC GIS Determine foundation height from desktop analysis Define project areas based on hydraulically connected areas Export data to FEMA BCA software to calculate annualized damages Identify and Estimate costs for mitigation measures

24 AT-RISK STRUCTURE INVENTORY

25 COUNTYWIDE MITIGATION PRIORITIZATION Identify Flood Prone Structures Data collection from multiple sources Property value info from County PVA Ground elevation data from LOJIC GIS Determine foundation height from desktop analysis Define project areas based on hydraulically connected areas Export data to FEMA BCA software to calculate annualized damages Identify and Estimate costs for mitigation measures

26 AT-RISK STRUCTURE INVENTORY

27 COUNTYWIDE MITIGATION PRIORITIZATION Identify Flood Prone Structures Data collection from multiple sources Property value info from County PVA Ground elevation data from LOJIC GIS Determine foundation height from desktop analysis Define project areas based on hydraulically connected areas Export data to FEMA BCA software to calculate annualized damages Identify and Estimate costs for mitigation measures

28 DETERMINE HIGHEST & LOWEST ADJACENT GRADES Determine HAG & LAG using ArcGIS ModelBuilder script Uses LOJIC Digital Elevation Model (DEM) with a 5 cell size created from 2012 LiDAR The script completely automates HAG/LAG determination (a few minutes for 12,000 structures)

29 COUNTYWIDE MITIGATION PRIORITIZATION Identify Flood Prone Structures Data collection from multiple sources Property value info from PVA Ground elevation data from LOJIC Determine foundation height from desktop analysis Define project areas based on hydraulically connected areas Export data to FEMA BCA software to calculate annualized damages Identify and Estimate costs for mitigation measures

30 DETERMINE FOUNDATION HEIGHT

31 DETERMINE FOUNDATION HEIGHT Compared Results to prior completed survey of 263 First Floor Elevations (FFE) of Repetitive Loss Structures (2012) Average difference was 0.3 Maximum difference was 2.4 and that was due to misclassification of the first floor on a split level home Standard Deviation = 0.86, therefore 68% are within % are within 1.72 Future task compare to ~2,000 EC database

32 COUNTYWIDE MITIGATION PRIORITIZATION Identify Flood Prone Structures Data collection from multiple sources Property value info from PVA Ground elevation data from LOJIC Determine foundation height from desktop analysis Define project areas based on hydraulically connected areas Export data to FEMA BCA software to calculate annualized damages Identify and Estimate costs for mitigation measures

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34 COUNTYWIDE MITIGATION PRIORITIZATION Identify Flood Prone Structures Data collection from multiple sources Property value info from County PVA Ground elevation data from LOJIC GIS Determine foundation height from desktop analysis Define project areas based on hydraulically connected areas Export data to FEMA BCA software to calculate annualized damages Identify and Estimate costs for mitigation measures

35 FEMA BENEFIT-COST ANALYSIS

36 COUNTYWIDE MITIGATION PRIORITIZATION Identify Flood Prone Structures Data collection from multiple sources Property value info from County PVA Ground elevation data from LOJIC GIS Determine foundation height from desktop analysis Define project areas based on hydraulically connected areas Export data to FEMA BCA software to calculate annualized damages Identify mitigation measures and estimate costs

37 COUNTYWIDE MITIGATION PRIORITIZATION Alternatives considered Acquisition Elevation on Foundation Walls Berms or Barrier walls Detention Basins Enlarging Culvert/Drainage Improvement Dry Floodproofing Wet Floodproofing

38 EXAMPLE PROJECT AREA BROOKLAWN TRIB Watershed Project ID Project Name Flooding Source South Fork Beargrass Creek SFBC001 Brooklawn Tributary Brooklawn Tributary Floodprone Primary Structures (100 yr) 58 Number of Claims 4 Value of Claims $8,725 Rep Loss Properties 0 SRL Properties 0

39 ANALYSIS AND RECOMMENDATION Annualized Damages Existing Conditions Annualized Damages with Annualized Loss Proposed Avoided Mitigation Alternatives # of Structure Present Worth Loss Avoided Present Worth Project Cost BCR Acquisition - Apartments/Condos 6 $6,688 $ - $6,688 $95,433 $1, Acquisition - Non- Residential 10 $12,306 $ - $12,306 $175,527 $9,357, Acquisition - Residential <0' 40 $10,785 $ - $10,785 $150,912 $5,505, Acquisition - Residential 0-2.9' 1 $612 $ - $612 $8,729 $114, Acquisition - Residential 3-5' 1 $12,559 $ - $12,559 $179,214 $182, Elevation on Foundation Walls 18 $22,497 $ - $22,497 $321,015 $4,122, Floodwall/Berm Dry Flood Proofing Wet Flood Proofing 23 $1,734 $ - $1,734 $24,743 $107, Channelization / Diversion Detention Basin $3,461,030 Recommendation: Acquisition for 1 structure whose flooding depth is between 3' & 5'

40 EXAMPLE PROJECT AREA HAYFIELD DUNDEE Watershed South Fork Beargrass Creek Project ID SFBC002 Project Name Flooding Source Hayfield-Dundee South Fork Beargrass Creek Floodprone Primary Structures (100 yr) 105 Number of Claims 114 Value of Claims $1,332,296 Rep Loss Properties 24 SRL Properties 0

41 ANALYSIS AND RECOMMENDATION Mitigation Alternatives # of Structure Annualized Damages Existing Conditions Annualized Damages with Proposed Annualized Loss Avoided Present Worth Loss Avoided Present Worth Project Cost Acquisition - Apartments/ Condos 8 $1,034 $ - $1,034 $14,753 $4,453,527 0 Acquisition - Non- Residential 4 $6,143 $ - $6,143 $87,652 $2,952, Acquisition - Residential <0' 70 $99,629 $ - $99,629 $1,421,665 $9,358, Acquisition - Residential 0-2.9' 22 $179,602 $ - $179,602 $2,562,820 $6,619, Acquisition - Residential 3-5' 1 $36,267 $ - $36,267 $522,756 $252, Elevation 58 $305,023 $55,291 $249,732 $772,704 $22,985, Floodwall/Berm $322,675 $106,136 $216,539 $3,089,874 $97,548, Dry Flood Proofing Wet Flood Proofing 12 $5,259 $ - $5,259 $75,112 $263, Channelization / Diversion Detention Basin Recommendation: Acquire the 2 properties with a BCR > 1 and Elevate 1 property with a BCR > 1 BCR

42 EXAMPLE PROJECT AREA EIFLER BEACH Watershed Ohio River Project ID Project Name OHIO001 Eifler Beach Flooding Source Ohio River Floodprone Primary Structures (100 yr) 10 Number of Claims 86 Value of Claims $1,495,824 Rep Loss Properties 4 SRL Properties 1

43 ANALYSIS AND RECOMMENDATION Mitigation Alternatives # of Structure Annualized Damages Existing Conditions Annualized Damages with Proposed Annualized Loss Avoided Present Worth Loss Avoided Present Worth Project Cost BCR Acquisition - Non- Residential 1 $13,182 $ - $13,182 $188,102 $337, Acquisition - Residential <0' 1 $2,530 $ - $2,530 $36,099 $642, Acquisition - Residential >5' 8 $98,778 $ - $98,778 $1,409,494 $2,409, Elevation on Foundation Walls 3 $7,235 $1,572 $5,663 $80,812 $1,239, Floodwall/Berm Dry Flood Proofing Wet Flood Proofing Channelization / Diversion Detention Basin Recommendation: Acquire the SRL property that has the 2 structures with BCR > 1; If FEMA grants become available, acquire the RL properties as well.

44 COMMUNITY RATING SYSTEM BENEFITS MSD is currently a Class 4, scheduled to be Class 3 on October 1 st, Flood Damage Reduction 520 Acquisition & Relocation 530 Flood Protection 610 Flood Warning & Response Flood threat recognition Emergency warning dissemination

45 PROJECT TAKEAWAYS / BENEFITS Louisville MSD can be more proactive in mitigating floodprone areas Projects are prioritized Wide range of alternatives, not just acquisition Cost effective mitigation solutions!

46 NEXT STEPS Complete remaining prioritization areas Determine Top 50 project areas and recommended mitigation measures Determine alternative funding sources Develop summary report & presentation Submit for grants or other funding sources as available to complete recommended projects

47 QUESTIONS?