City of Fortuna Rohner Creek Flood Control Project

Transcription

1 City of Fortuna Rohner Creek Flood Control Project Presented To: Fortuna City Council Special Session April 26, 2013 Presented By: Merritt Perry, PE Jeremy Svehla, PE Robert Holmlund, AICP

2 Presentation Overview 1. Review Project Background and Need 2. Public Outreach Survey Results 3. Overview of Project Studies 4. Description of Project Alternatives 5. Process for Ranking Alternatives 6. Next Steps

3 2. Project Needs/Benefits and Background

4 Rohner Creek Project Need and Opportunities Reduce Flooding Reduce Property Damage Through Streambank Stabilization and Restoration

5 Rohner Creek Project Need and Opportunities Establish Plan for Maintenance and Management of Rohner Creek Opportunities to Improve Fish Passage, Instream Habitat and Water Quality

6 Timeline of Rohner Creek Major Flooding Major Flooding Minor Flooding FEMA Mapping Storm Drain Master Plan Minor Flooding Minor Flooding Bond Measure Storm Drain Master Plan Minor Flooding Prop 1E Grant: Current Project 1950s 1960s 1970s 1980s 1990s 2000s 2010s

7 Timeline of Current Project Past Streamflow Gaging and Preliminary Hydraulic Analysis Prop 1E Grant Award Present Environmental Studies Stakeholder Outreach 10% Design of Alternatives Selection of Alternatives Future Finalize DWR Prop 1E Grant Contract Complete Engineering Design Bidding and Construction

8 3. Results of Property-owner Outreach Process

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11 160 properties

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13 160 surveys 55 respondents >33% response rate Dozens of additional s, phone calls, and meetings

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15 How Long Have You Owned and/or Resided on this Property? More than 15 years 70% Less than 5 Years 2% Between 10 and 15 9% Between 5 and 10 19%

16 80% have lived in study area for over 10 years

17 What is the Frequency at which Your Property Experiences Flooding? More than once each year 8% Once each year 6% Not Sure 10% Once every 10 years 13% Never 54% Once every 5 years 9%

18 36% have experienced flooding (10% unsure) 12% experienced flooding at least once each year

19 Do You Pay Flood Insurance? Yes 24% No 76%

20 36% have experienced flooding 24% pay flood insurance

21 Describe the Location in which Flooding Occurs on Your Property Driveway 25% Other 14% Yard or pasture 22% Perimeter of house 23% Out structure 14% Inside house 2%

22 39% of flooding impacts structures

23 If Your Property Experiences Flooding, what is the Average Typical Duration of Flood Inundation? Not Sure 23% Less than 12 hours 19% More than 24 hours 16% Between 12 and 24 hours 42%

24 77% of flooding last more than 12 hours

25 Has Your Property Ever Experienced Damage Due to Flooding? Yes 23% No 77%

26 36% have experienced flooding 23% have experienced damage due to flooding 64% of flooding causes damage

27 Do You Think Your Property is Likely to Flood Again in the Future Without Corrective Action? Not Sure 28% No 35% Yes 37%

28 Has Flooding Hindered Your Ability to Develop or Sell Your Property? Yes 15% No 85%

29 Do You Have Any Development Plans for Your Property that Could be Impeded by Potential Flooding? Yes 14% No 86%

30 Identify all the Flood Control Measures You, the City, or Others Have Implemented on Your Property None 46% Lifted buildings 4% Retaining walls 9% Streambed (rocks sandbags) 13% Other 26% Berms 2%

31 From Your Perspective, What has been the Cause of Flooding on Your Property? existing bridges Plugged 6% culvert 9% Other 8% dense vegetation 29% capacity of stream too small 21% debris 27%

32 Summary of Comments Received

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34 Theme 1: Trees and debris in creek cause flooding.

35 Theme 2: Flooding is experienced in some areas and not others. For those experiencing flooding, the problem can be very bad. For those not experiencing flooding, flood insurance seems like a waste of money.

36 Theme 3: There are concerns about including portions of the project on private property. Concern - Losing usable land and/or improvements Concern - Increased maintenance Benefit - Reducing flood issues Benefit Creating usable land

37 Theme 4: There are many ideas regarding how to fix the flooding problems. Widen channel Deepen channel Retaining walls Berms Creek maintenance Bank stabilization Better street drainage

38 3. Project Studies

39 Project Special Studies 1. CDFW Electrofishing 2. Fish Passage Assessment 3. Rare Plant Survey 4. Wetland Delineation 5. Riparian Habitat Mapping 6. Cultural Resource Search 7. Phase 1 Corridor Study 8. Hydraulic Analysis

40 Hydrologic and Hydraulic Analysis and Calibration

41 Hydrologic and Hydraulic Analysis Calibration Observed Rainfall Predicted Flow without Calibration Observed Flow Predicted Flow with Calibration

42 Existing Conditions: Rohner Creek 100 year flow

43 Existing Conditions: Rohner Creek 100 year flow Maximum Inundation (Feet) < > 2

44 4. Overview of Alternatives Considered

45 Alternative 1: Improved Channel 10 year flow conveyance

46 Alternative 1: Improved Channel 10 year flow conveyance

47 Alternative 2: New Rohner Creek Alignment 100 year flow conveyance

48 Alternative 3: Improved Channel with Field Bypass Culvert 100 year flow conveyance

49 Alternative 4: Improved Channel with Fortuna Blvd Bypass Culvert 100 year flow conveyance

50 Initial Stakeholder Feedback 1. Property Owners Many understand project need and desire improvements Most are willing to work with the City Some are against losing property 2. Regulatory Agencies Prefer Alternative that Mimics Natural System Minimize Bypass Length 3. DWR (Prop 1E Grant) Require Minimum 10-year flow conveyance Seismic Retrofit Improvements

51 5. Alternatives Analysis Process

52 Alternative Analysis Steps 1. Finalize the four project alternatives 2. Define rating criteria 3. Determine a weight for each criteria 4. Score each alternative by calculating how well each alternative satisfies each criteria

53 Rating Criteria Flood Reduction Private Property Impacts Cost Operations and Maintenance Requirements (O&M) Environmental Constraints

54 Flood Reduction Privately and Publically-owned parcels Roads and other City infrastructure

55 Private Property Impacts Temporary construction occupation Permanent (Lease, easement, ROW, etc)

56 Cost Construction Cost Land Acquisition Cost (leases, easements, ROW) Operations and Maintenance Cost

57 Environmental Impacts Regulatory approval and permitting difficulty Ecological Function/ In-stream Habitat/ Fish Passage

58 Operation and Maintenance Requirements Accessibility to facilities by City Public Works Staff Effort required of City Public Works Staff Vulnerability to Failure ( Durability ) Adaptability to Alterations ( Resiliency )

59 Rating Criteria CRITERIA ALT X ALT Y ALT Z Flood Reduction Private Property Impacts Cost Environmental Impacts Operations and Maintenance TOTAL

60 Rating Criteria CRITERIA WEIGHT ALT X ALT Y ALT Z Flood Reduction Private Property Impacts Cost Environmental Impacts Operations and Maintenance TOTAL

61 Rating Criteria Flood Reduction Private Property Impacts Cost Operations and Maintenance Requirements (O&M) Environmental Constraints Other (e.g. Long-term City Vision/Goals?)

62 6. Next Steps

63 Next Steps Project team to finalize alternatives analysis report including cost estimating and ranking and submit to Council in late May Council to select an alternative June 3rd Engineering Design July 2013 through July 2014 Construction 2015

64 Discussion Topics Alternatives Criteria Flood Reduction Private Property Impacts Cost Operations and Maintenance Requirements (O&M) Environmental Constraints Other (e.g. Long-term City Vision/Goals?)

65 Discuss Alternatives Alternative 1 Alternative 2 Alternative 3 Alternative 4

66 Discuss Rating Criteria Flood Reduction Private Property Impacts Cost Operations and Maintenance Requirements (O&M) Environmental Constraints Other (e.g. Long-term City Vision/Goals?)