September 20, Stormwater Management Division

Transcription

1 TFMA Fall Conference September 20, 2012 Steve Eubanks, P.E., CFM Ranjan S. Muttiah, Ph.D, P.E. City of Fort Worth Stormwater Management Division Terry M. Barr, P.E., CFM Sam Hinojosa, P.E., CFM Halff Associates, Inc.

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3 Open Channel Study Goals Improve Effective Modeling Data Use Consistent Methodologies and Assumptions Use Recent Terrain and Base Map Information Survey Channel Sections and Structures Study Unmapped Open Channels Detailed Modeling of Unstudied Streams Compile Models and Supporting Data Evaluate Flood Mitigation Alternatives Provide Conceptual Cost Estimates Identify Critical Project and Set CIP Priority for Others

4 Fort Worth StormwaterStudies Open Channel Studies 31 Under Contract 15 at 75% Review 5 at 90% Review 3 RAMPP, 2 TRWD Neighborhood Studies 9 in Progress Watershed Planning Studies 5 InfoWorks SD/2D Studies

5 Open Channel Study Tasks Task 1: Project Management Task 2: Data Search, Collection, Field Investigation Task 3: Hydrologic Analysis Task 4: Hydraulic Analysis Task 5: Watershed Flood Hazard Assessment Task 6: Proposed Flood Mitigation Alternatives Task 7: Quality Assurance/Quality Control Task 8: Letter of Map Revision (LOMR)

6 Task 2: Data Collection Data Search and Collection Effective Models and Mapping Design Reports and Plans GIS and Terrain Information Historical Flood Complaints Field Reconnaissance Channel/Structure Survey Stream Condition Assessment Evaluation of channel condition Erosion potential at structures

7 Stream Condition Assessment Field Investigation Photograph and Document Conditions Assess Channel Condition Good, Fair, Poor Areas of Imminent Failure Scour at Hydraulic Structures More Detailed Evaluation at City Request

8 Drainage Complaints Gather records of drainage complaints in the watershed Comparison for Existing Results Minor Drainage Projects

9 Task 3: Hydrology Coordinated Basin Delineation Update Hydrologic Models Existing and Fully Developed Q s Storm Sewer Capacity Neighborhood Attenuation Parameter Consistency Loss Methodology Hydrograph Transform Hydrologic Routing Georeferenced Models Comparison to Effective Q s

10 Task 4: Hydraulics Update Hydraulic Models Cross Section Layouts Terrain and Survey Data Manning s n Guidelines Hydraulic Structures Encroachment Analysis Floodplain Mapping Existing Conditions Fully Developed Advanced Modeling

11 Task 5: Hazard Assessment Inundation Frequencies at Crossings Areas of Regular Flooding At-Risk Structures High Velocities

12 Task 6: Flood Mitigation Preliminary Alternative Identification Discussion with City & Consultant Identify External Factors and Stakeholders FW PACS, Gas Companies, TxDOT Select Alternatives for Development H&H Modeling Gauge Effectiveness Identify Potential Impacts Provide Conceptual Cost Estimate Benefit Cost Analysis

13 Benefit Cost Analysis Survey FFE s of Floodplain Structures Most Common Benefit/Cost Methods FEMA USACE Factors Not Considered Roadway Accessibility Intangibles (Vehicle Damage, Productivity Loss) Political Pressure Needs to be based on more than just Property Values

14 Task 7: QA/QC Review of Models, Report Content, Formatting 75% Review Completion of Tasks % Review Completion of Task 6 100% Review Completion of all tasks Multiple Reviewers Halff Associates Program Manager Fort Worth Stormwater Management Fort Worth Floodplain Administrator

15 Task 8: Letter of Map Revision At Floodplain Administrators Discretion Existing Floodplain Limits Potential for Development Number of Structures Affected No Effective Floodplain

16 Study Program Findings

17 Stream Condition Rating

18 Drainage Area Comparison

19 100-Yr DischargeComparison

20 Normalized Q 100 Flows

21 Normalized Q 5 Flows

22 BFE Comparison

23 Level of Service at Crossings

24 SC-7/EdgecliffFloodplain -FIS 134 buildings

25 SC-7/EdgecliffFloodplain -CFW 18 buildings

26 Cottonwood Floodplain -FIS 59 buildings

27 Cottonwood Floodplain -CFW 48 buildings

28 Floodplain Area Comparison

29 Flooded Structure Comparison

30 Mitigation Alternatives BCA s generally less than 1.0 Mitigation Alternatives Detention Basins Upsize Road Crossings Stream Widening or Lowering Home Buy-Outs Development of Feasibility Options Matrix

31 Acknowledgements Floodplain Administration Clair Davis, P.E., CFM Amy Cannon, P.E, CFM Consultants AECOM ANA Consultants, LLC Baird, Hampton & Brown Brown & Gay Engineers CDM-Smith CP&Y Dunaway Associates Freese& Nichols, Inc. Halff Associates, Inc. HDR Engineering, Inc. Jacobs James DeOtte Engineering Jerry Parche Consulting Kimley-Horn Associates LAN, Inc. MultaTech SAIC, Inc. S&B Infrastructure Teague, Nall & Perkins TranSystems URS Corporation Wade Trim