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Cover PageTECHNICAL MANUALHydraulics ManualMay 28, 2015Hydraulics Unit

TECHNICAL MANUALHydraulics ManualAdopted: May 28, 2015Latest Revision: May 28, 2015Contributing Authors:Nick Wark, P.E., CFM, VTrans Hydraulics EngineerKelly Smith, VHBMatthew Kennedy, P.E., VHBSarah Widing, P.E., VHBJacob San Antonio, P.E., VHBRobert Wildey, VHBVermont Agency of TransportationOne National Life DriveMontpelier, VT 05633-5001802.828.2657VHB101 Walnut StreetWatertown, MA 02471617.924.1770

About the ManualThe intent of the VTrans Hydraulics Manual is to identify approaches to the analysis of road and highway hydraulics that areapproved for use by VTrans. This manual is not intended to be a comprehensive summary of all available techniques forhydrologic and hydraulic analysis, but rather it is meant to provide the designer with (1) guidance on the use of selected methodsand (2) references to sources of additional information.The methods presented in this manual make reference to other guidance documents and engineering manuals, such as thoseproduced by the American Association of State Highway and Transportation Officials (AASHTO), the Federal HighwayAdministration (FHWA), the U.S. Army Corps of Engineers (USACE), the U.S. Geological Survey (USGS), and the VermontAgency of Natural Resources (ANR) that provide more comprehensive explanations of the methods along with the scientificbasis. VTrans recommends that designers make use of the latest revisions of these manuals when performing calculations.Computing power has dramatically increased in recent years, so most of the methods that are covered in this manual can beperformed using free applications that were developed by federal agencies using the methodologies outlined in their respectiveguidance documents. The benefit of using software is the ability to perform multiple iterations easily, allowing different designscenarios to be compared quickly and accurately.As a living document, VTrans intends to provide periodic updates to this manual, which may include replacing individual pages orsections as new information or techniques become available. Periodically check the VTrans website to download manual updates.OutlineThe following outline provides a brief description of each chapter in the manual. The final sections of the manual are devoted tosummarizing materials—a list of acronyms, definitions of key terms, references, and an index.Chapter 1 Hydraulic Design Guidelines presents an overview of the key guidelines that should be considered whenpreparing a hydraulic design.Chapter 2 Planning and Location identifies the planning and permitting considerations that must be addressed prior toand throughout the design process.Chapter 3 Data Collection, Resources, and Tools provides an overview of the data collection requirements fordifferent types of hydraulic structures. This chapter summarizes key resources and tools referenced throughout the manualand incorporates lists to assist the designer and reviewer in confirming that necessary information has been gathered andconsidered during the design process.Chapter 4 Hydrology identifies the preferred methods of hydrologic analysis and their proper application. The resultsfrom the hydrologic analysis are a critical component of the project and ultimately inform the remainder of the designprocess.Chapter 5 Open Channels provides guidance for evaluating flow in open channels and appropriate measures to use indesigning stable open-channel drainage systems. Two key FHWA Hydraulic Engineering Circular (HEC) publications aregiven as the basis for open channel design: HEC-14, “Hydraulic Design of Energy Dissipation for Culverts and Channels,” andHEC-15, “Design of Roadside Channels with Flexible Linings”.About the Manuali

Chapter 6 Crossing Structures highlights the analysis tools that are most helpful in the design of bridges and culverts.Emphasis is placed on using the USACE’s Hydraulic Engineering Center River Analysis System (HEC-RAS) software forbridge analysis and design and the FHWA’s HY-8 software for culvert analysis and design.Chapter 7 Channel Stability and Scour at Bridges provides guidance on the evaluation of flow through and aroundbridges. Three key FHWA HEC publication are given as the basis for bridge scour analysis and protection: HEC-18,“Evaluating Scour at Bridges,” HEC-20, “Stream Stability at Highway Structures,” and HEC-23, “Bridge Scour and Stream InstabilityCountermeasures: Experience, Selection, and Design Guidance.”Chapter 8 Storm Drainage Systems is concerned with the specifics of clearing stormwater runoff from pavement toensure safe travel conditions. Guidance is provided for the design and analysis of drainage infrastructure such as catch basingrates, curb and gutter sections, and closed drainage systems. FHWA’s HEC-22, “Urban Drainage Design Manual,” isreferenced as the basis for stormwater drainage system design. Reference is also made to the most recent version of theANR “Vermont Stormwater Management Manual” (VSMM) for the appropriate design of stormwater treatment facilities(stormwater wetlands, wet ponds, infiltration systems, etc.) for use in Vermont.Chapter 9 Documentation identifies the backup calculations, maps, reports, and types of other documentation that mustbe assembled by the designer and provided to VTrans as part of a complete design package.Appendix A Manning’s n Values provides a summary of typical Manning’s n values used as part of hydraulic analyses.Appendix B Field Investigation Forms includes copies of the VTrans Field Investigation Form and the Hydraulic SurveyField Inspection Checklist. The Field Investigation is also available electronically for use with spreadsheet software.Appendix C Hydraulics Form includes two copies of the VTrans Final Hydraulics Report Form—one version offeringguidance for filling out the form, and one version that is blank. The Final Hydraulics Report Form should be used tosummarize the hydraulic performance of existing and proposed crossing structures with clear spans of 6 feet or greater. Itcan also be used for structures with clear spans that are less than 6 feet if site conditions warrant the level of detail. All ofthe information from this form should be included on project plans. The Final Hydraulics Report Form is availableelectronically for use with spreadsheet software.About the Manualii

Table of ContentsCover Page . 1About the Manual . iTable of Contents . iiiList of Tables . xList of Figures . xiChapter 1 Hydraulic Design Guidelines . 1-11.11.21.31.41.5Introduction .1-11.1.1 Overview .1-11.1.2 Criteria, Guidelines, and Guidance .1-1Hydrologic Analysis Guidelines .1-11.2.1 Introduction .1-11.2.2 Background Information .1-11.2.3 Floodplain/Flood Hazard Areas .1-21.2.4 Factors Affecting Flood Flows .1-21.2.5 Hydrologic Methods .1-21.2.6 Design Frequency .1-2Hydraulic Analysis Guidelines .1-31.3.1 Introduction .1-31.3.2 Hydraulic Analysis .1-31.3.3 Engineering Evaluation .1-31.3.4 General Guidelines .1-31.3.5 Auxiliary Openings for Flood flow .1-4Geomorphic Analysis Guidelines .1-51.4.1 Introduction .1-51.4.2 Location of Stream Crossing .1-51.4.3 Stream Morphology and Scour .1-51.4.4 Flood and Fluvial Erosion Hazards .1-5Other Considerations .1-61.5.1 Environmental Considerations .1-61.5.2 Future Hydrologic Projections .1-61.5.3 Construction/Maintenance .1-61.5.4 Agency Coordination .1-61.5.5 Documentation .1-7Chapter 2 Planning and Location . 2-12.12.2Introduction .2-12.1.1 Scope and Complexity.2-12.1.2 Components of Hydraulic Design Process .2-12.1.3 Permitting Considerations .2-22.1.4 Potential Constraints .2-3Design Considerations .2-32.2.1 Location Considerations .2-32.2.2 Interagency Coordination .2-3Table of Contentsiii

2.32.2.3 Intra-agency Coordination .2-3Initial Data Review .2-42.3.1 Drainage Surveys .2-42.3.2 Data Collection .2-42.3.3 Next Steps .2-4Chapter 3 Data Collection, Resources, and Tools . 3-13.13.23.33.43.53.63.73.8Introduction .3-1Required Data.3-13.2.1 Overview .3-13.2.2 Watershed Characteristics .3-13.2.3 Site Characteristics.3-3On-Site Data Collection .3-53.3.1 Field Inspection.3-63.3.2 Hydraulic Surveys .3-63.3.3 Documentation .3-6Data Evaluation.3-63.4.1 Objective .3-63.4.2 Evaluation .3-73.4.3 Sensitivity .3-7Resources .3-73.5.1 Federal Highway Administration.3-73.5.2 American Association of State Highway Transportation Officials . 3-73.5.3 Natural Resources Conservation Service .3-73.5.4 Vermont Agency of Natural Resources .3-7Data Sources .3-83.6.1 Federal Emergency Management Agency .3-83.6.2 U.S. Army Corps of Engineers .3-83.6.3 Vermont Center for Geographic Information . 3-8Data Tools .3-83.7.1 U.S. Geological Survey.3-83.7.2 U.S. Army Corps of Engineers .3-9Design Tools .

Appendix C Hydraulics Form. includes two copies of the VTrans Final Hydraulics Report Form—one version offering guidance for filling out the form, and one version that is blank. The Final Hydraulics Report Form should be us ed to summarize the hydraulic performance of existing and propo