TFMA Fall ConferenceTFMA Fall Conference

September 20, 2012

Steve Eubanks, P.E., CFM Terry M. Barr, P.E., CFM

Ranjan S. Muttiah, Ph.D, P.E. Sam Hinojosa, P.E., CFM

City of Fort Worth Halff Associates, Inc.

Stormwater Management Division

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� 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

Fort Worth Stormwater Studies� Open Channel Studies

� 31 Under Contract

� 15 at 75% Review

� 5 at 90% Review5 at 90% Review

� 3 RAMPP, 2 TRWD

� Neighborhood Studies

� 9 in Progress

� Watershed Planning Studies

� 5 InfoWorks SD/2D Studies

Open Channel Study Tasks

� Task 1: Project Management

� Task 2: Data Search, Collection, Field Investigation

� Task 3: Hydrologic Analysis

� Task 4: Hydraulic 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)

Task 2: Data Collection

� Data Search and Collection� Effective Models and Mapping

� Design Reports and Plans

� GIS and Terrain Information

� Historical Flood Complaints� Historical Flood Complaints

� Field Reconnaissance

� Channel/Structure Survey

� Stream Condition Assessment� Evaluation of channel condition

� Erosion potential at structures

Stream Condition Assessment

� Field Investigation

� Photograph and Document Conditions

� Assess Channel Condition

� Good, Fair, Poor� Good, Fair, Poor

� Areas of Imminent Failure

� Scour at Hydraulic Structures

� More Detailed Evaluation at City Request

Drainage Complaints

� Gather records of drainage complaints in the watershed

� Comparison for Existing Results

� Minor Drainage Projects

Task 3: Hydrology

� Coordinated Basin Delineation

� Update Hydrologic Models

� Existing and Fully Developed Q’s

� Storm Sewer Capacity

� Neighborhood Attenuation� Neighborhood Attenuation

� Parameter Consistency

� Loss Methodology

� Hydrograph Transform

� Hydrologic Routing

� Georeferenced Models

� Comparison to Effective Q’s

Task 4: Hydraulics

� Update Hydraulic Models

� Cross Section Layouts

� Terrain and Survey Data

� Manning’s ‘n’ Guidelines

� Hydraulic Structures� Hydraulic Structures

� Encroachment Analysis

� Floodplain Mapping

� Existing Conditions

� Fully Developed

� Advanced Modeling

Task 5: Hazard Assessment

� Inundation Frequencies at Crossings

� Areas of Regular Flooding

� At-Risk Structures

� High Velocities

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� Select Alternatives for Development

� H&H Modeling

� Gauge Effectiveness

� Identify Potential Impacts

� Provide Conceptual Cost Estimate

� Benefit Cost Analysis

Benefit Cost Analysis

� Survey FFE’s of Floodplain Structures

� Most Common Benefit/Cost Methods

� FEMA

� USACE

Factors Not Considered� Factors Not Considered

� Roadway Accessibility

� Intangibles (Vehicle Damage, Productivity Loss)

� Political Pressure

� Needs to be based on more than just Property Values

Task 7: QA/QC

� Review of Models, Report Content, Formatting

� 75% Review – Completion of Tasks 1-5

� 90% Review – Completion of Task 6

� 100% Review – Completion of all tasks100% Review – Completion of all tasks

� Multiple Reviewers

� Halff Associates – Program Manager

� Fort Worth Stormwater Management

� Fort Worth Floodplain Administrator

Task 8: Letter of Map Revision

� At Floodplain Administrators Discretion

� Existing Floodplain Limits

� Potential for Development

� Number of Structures Affected

No Effective Floodplain� No Effective Floodplain

Study Program Findings

Stream Condition Rating

Drainage Area Comparison

100-Yr Discharge Comparison

Normalized Q100 Flows

Normalized Q5 Flows

BFE Comparison

Level of Service at Crossings

SC-7/Edgecliff Floodplain - FIS

134 buildings

SC-7/Edgecliff Floodplain - CFW

18 buildings

Cottonwood Floodplain - FIS

59 buildings

Cottonwood Floodplain - CFW

48 buildings

Floodplain Area Comparison

Flooded Structure Comparison

Mitigation Alternatives

� BCA’s generally less than 1.0

� Mitigation Alternatives

� Detention Basins

� Upsize Road Crossings� Upsize Road Crossings

� Stream Widening or Lowering

� Home Buy-Outs

� Development of Feasibility Options Matrix

Acknowledgements

� Floodplain Administration

� Clair Davis, P.E., CFM

� Amy Cannon, P.E, CFM

� Consultants

AECOMANA Consultants, LLCBaird, Hampton & BrownBrown & Gay EngineersCDM-SmithCP&YDunaway AssociatesFreese & Nichols, Inc.

Halff Associates, Inc.HDR Engineering, Inc.JacobsJames DeOtte EngineeringJerry Parche ConsultingKimley-Horn AssociatesLAN, Inc.MultaTech

SAIC, Inc.S&B InfrastructureTeague, Nall & PerkinsTranSystemsURS CorporationWade Trim