INDOT Hydraulic Engineering designs or reviews all waterway projects including, but not limited to, bridges, culverts, storm sewers, and detention ponds along state roads, U.S. routes or interstates or local projects built with state or federal funds.  

Index

• Developing Design Guidance
• Submitting Documents
• Prequalification to Submitting Projects
• Upcoming Training
• Related Links and Documents
• Frequently Asked Questions
• Contact Information

• Bridge
  • For a scour analysis and if a bridge is on piles, the traditional "10 foot rule from the bottom of the piles" is no longer used.  If a the piles are in anyway exposed during a scour event, the scour determination is sent to part B of the scour memo and the bridge structure engineer at INDOT will determine the scour criticalness.  If the piles are undermined, then the bridge may be determined scour critical from the hydraulic engineer.
  • When conducting scour design, the IDM states to use the channel only, however due to the fluctuation of channel embankments, it may not be the highest value of the calculations. Therefore the greatest contraction scour depth between the left, right or center values found in Hec-RAS should be used when reporting the scour depth.
  • Existing single span structures greater than or equal to 20 ft and up to 30 ft in perpendicular span to the conveyed channel may have proposed structures sized in HY-8 version 7.2. This only applies to proposed structures that can be modeled in HY-8 using a pre-defined HY-8 shape in the culvert data section of the crossing data input, and have a perpendicular span to the conveyed channel within the aforementioned span range.  The Office of Hydraulics must be consulted before modeling slab-top structures within the aforementioned span range
    • Note: Three-sided and four-sided concrete structures that are less than 18 ft in perpendicular span to the conveyed channel will still need to be modeled with HY-8 incorporating haunches using the user defined shape options.
  • The scour protection for vertical abutment bridges in Figure 203-3B is no longer in effect to where the riprap should have a lay width twice the water depth or a minimum of 10 ft. Please follow Standard Drawing E723-CCSP-04 of using a minimum width of 6 ft from the edge of the footer.
• Small Structure
  • CLARIFICATION OF IDM 203-2.02(02) 2.a.1.: The replacement structure does not have to have the same span as the existing structure when the existing structure is going from pipe to a proposed box type structure.  However, the cross-sectional structure area cannot be reduced.
    • Example:  An existing twin 8 foot diameter pipes may be replaced with a proposed 15x7 box structure, even though the twin pipes have a total span of 16 feet while the box has 15 feet, as long as the proposed total area is equal to or greater than the existing.  In this case, the existing area is about 101 square feet, while the proposed box (with haunches) has an area of 103 square feet.
    • Example 2:  An existing 6 foot diameter pipe cannot be replaced with a 5x5 box because the existing pipe has an area of 28 square feet, while the proposed box (with haunches) has an area of 23 square feet.
  • The invert of a jack and bored pipes will be set to a minimum of 1 ft above the invert of the existing pipe to be lined.  If this is not feasible due to site constraints, please coordinate with the INDOT Hydraulic Engineering.
  • All liner options should have the inverts of the pipes raised by the liner thickness.  Backwater should then be calculated by taking the existing culvert's backwater and subtract the difference of the headwaters.
  • HY-8 v.7.2 is currently the only version permitted for use by the INDOT Hydraulic Engineering.  Please click the following link to download the software. (Active Design Memoranda16-34).
    • Due to Window's updates, HY-8 v.7.2 will not install without first installing the  application that can be downloaded by clicking here. After this application is installed, HY-8 v.7.2 may be installed.
  • Jack and bore pipes as part of a culvert liner project under the interstate are required to have a minimum inner diameter of 18 inches.
  • For consistency of sump requirements and without more detailed information, if the soil map unit description contains the word sand, the required sump from IDM Fig 203-2E should be based off of the "Sump Required for Stream Bed of Sand" column.
  • Reinforced concrete boxes and 3 sided structures under 18 foot span should incorporate corner haunches as produced by the manufacturer.  The spreadsheet provided below, named Specialty Structure Coordinate Generator under Other Links and Forms, includes the haunch data from the manufacturers.
  • A flow chart has been developed to help designers select which structure and liner options should be analyzed.  Modeling guidance has also been included.  This chart can also be found as Proposed Structures Flow Chart under Other Links and Forms below.
    • Semi-smooth options will no longer be required to be given as replacement options for small structures.
  • All three-sided structures are no longer required to be sumped unless requested by the county surveyor for legal drains.
  • When analyzing an existing structure that is showing overtopping, the designer should NOT artificially raise the road to analyze headwater elevation as it may exaggerate the backwater total, but rather make certain that the discharge through the liner/new pipe at overtopping is greater than the existing.
  • For a culvert rehabilitation project, a pipe liner should not be used if it has a inner diameter less than the minimal allowable for the particular roadway facility.  See IDM Figure 203-2B.  If the host pipe is a median drain or storm sewer, the pipe liner should not have an inside diameter less than 12".
• Hydrology
  • If a dual hydrologic soil group is within a watershed, then the soil should be considered undrained (D-soil) unless it can be shown that the water table is more than 24 inches below the ground surface. If desired, the groundwater depth can be found using the USDA Websoil survey.

• Design Guidance
  • Archived Project's Plan Request
  • Bevel Edge Headwall Figures
  • BIAS
  • Culvert Inlet Coefficients
  • Driveway Permit Manual
  • HEC-RAS Bridge and Scour Modeling Procedures
  • Indiana Design Manual
  • INDOT Driveway Permit Checklist
  • Standard Drawings
  • Waterway Permit Manual
• Hydrology Links
  • DNR Coordinated Discharges
  • DNR Floodplain Information Portal
  • DNR Hydraulics Model Library
  • DNR Peak Discharge Determination System
  • IN County Surveyor Directory
  • Indiana Spatial Data Portal
  • NOAA Precipitation Frequency Estimates
  • NOAA - Vertcon
  • Purdue Regression
  • USDA NRCS Soil Surveys
  • USGS Streamstats v4
• Other Links and Forms
  • 5" Paved Invert Worksheet
  • CIPP Lining Worksheet
  • Elliptical HDPE Pipe Lining Worksheet
  • Field Data Form
  • Huff Distribution Regions
  • INDOT Driveway Permit Checklist
  • INDOT Method Inlet Spacing Worksheet
  • IDM Figure 203-4I - INDOT Storm Drain Computation Worksheet
  • INDOT Traffic Count Database System
  • Minimum Culvert Cover Worksheet
  • Proposed Structures Flow Chart
  • IDM Figure 202-3C - Regional Multipliers GIS Layers - EP 0.2%
  • Safety Briefing Form
  • Specialty Structure Coordinate Generator
  • IDM Figure 203-5A - Summary Performance Table for Storage
  • IDM Figure 202-2A - TR-55 Time of Concentration Worksheet
  • TR-20 Input Files
• Past Presentations
  • Hydraulics Presentation - County Bridge Conference 2016
  • Hydraulics Presentation - Bridge Hydraulics Parameters 2014
  • Hydraulics Presentation - Storm Damage - Floating Culverts 2016
  • Hydraulic Training Conference - February 7, 2017
    • IDM Updates 
    • Pipe Liners 
    • Small Structure Replacement 
    • Drainage Area & Discharge Determination
    • Hydraulic Data - Bridges
  • Hydraulics IDM Updates - Road School 2017
  • Small Structures Rehabilitation Design - CEPDS 2018
  • LPA Design Policy Changes - CEPDS 2018
  • Scour Reports - CEPDS 2018
  • Hydraulic Training Conference - December 2019
    • Median Drain 
    • Bridge Hydraulic Pointers 
    • Common Errors in Small Structure Hydraulics
    • INDOT Hydraulics Training Courses
    • Small Structure Memorandum Template Guidance
  • Detention Design - CEPDS 2020
  • HRA and How to Use It - INDOT Highway Design Conference
  • INDOT Hydraulics Process  Modernization and Policy Updates - CEPDS 2021

• When doing a bridge scour analysis, should I take the depth from the downstream invert or upstream invert?

  When doing a bridge scour analysis, the scour depth should be taken from the lowest invert elevation, whether it is upstream or downstream.

• What kind of inlet type should I choose when lining a pipe?
  • When initially lining a pipe with CIPP, the inlet configuration should match whatever is in the field, unless the existing pipe is projecting. In which case, the liner should have an inlet configuration of mitered to conform to slope. 
  • When initially lining a pipe with HDPE liner, the inlet configuration should have an inlet configuration of mitered to conform to slope even if the existing pipe has a headwall. If a headwall or bevel edge is needed for the HDPE liner to perform correctly, it will need to be constructed with the project.
  • If you are putting in a 5" paved invert, the inlet configuration should simply match the existing configuration.  If you need to improve the inlet configuration, then adding a headwall or a headwall with bevel edge is acceptable with the proposal.
• HY-8 v.7.2 does not allow me to perform culvert analysis with reverse slope pipes. What should I do when the existing pipe has the inlet lower than the outlet?

  If the existing pipe has a reverse slope, we recommend bringing the inlet invert to the elevation of the outlet creating a flat pipe.

• What type of inlet configuration do I use for a pipe end section? (metal, grated box, etc.)

  Inlet configurations for the pipe end sections: grated box types I and II, metal end sections, precast concrete, and safety metal culvert end sections for smooth pipes is recommended to have a the inlet configurations similar to that of a headwall.

• What region of the Huff Distribution Curve does my project correspond to?

  The 50% Huff Distribution Curves have been set in four locations within the state of Indiana.  For consistency purposes, this map - Huff Distribution Regions - shows which county belongs to which region.

• Which quartile of the Huff Distribution Curve do I use for hydraulic analysis?

  According to the LTAP Stormwater Drainage Manual, the first quartile is set for any storm duration less than or equal to 6 hours.  The second quartile is set for any storm duration greater than 6 hours and up to and including a 12-hour storm.  The third quartile is for storms greater than 12 hours and up to and including a 24-hour storm.  The fourth quartile is for any storm greater than 24 hours.

• Which velocity, average or max, should be used in determining scour protection for bridges?

  Scour protection for bridge design and rehab is based primarily on the following criteria (based on IDM Fig. 203-2J and Fig 203-3B):

  • The abutments shall be protected with a minimum size rip rap to that of the average velocity of the bridge.
  • The piers shall be protected with a minimum size rip rap to that of the max velocity of the bridge determined by velocity distribution.
• What is the minimum pipe size for a paved invert option?

  The minimum pipe size for a paved invert rehabilitation is for the existing pipe to have a minimum span and rise of 4 ft.

• How do I know if I need a Construction in a Floodway (CIF) permit for a project?

  A flow chart has been created to help determine if a CIF permit is required for a project.  CIF Permit Criteria Flow Chart

• How should I present the size of a 3-sided structure in a hydraulics memo?

  A 3 sided structure, whether it is a flat top, arch top, or slab top, should have its low structure elevation, flow line elevation, and sump labeled in the hydraulics memo with their respective line in the table.  The span should be labeled within the type of structure line.  To avoid confusion, the rise of the structure should not be stated as the flow line elevation, sump depth, and low structure elevation will be the necessary information for the structural and environmental engineer to use in the designs.

• What size particle should I use for scour analysis if I do not have a soil borings report?

  When using live bed scour for standard stream crossings, please use the minimum standard 0.01 mm for the d₅₀ soil size. If the structure is an overflow structure, then clear water scour should be used and HEC-18 updated in 2012 now states to use 0.2 mm as a minimal size for the d₅₀ soil size. If the structure is both a natural stream and an overflow structure for a larger stream, then both scour types should be checked under their respective flow rates and soil sizes and the larger scour result should be used.

• Do I need to send my median drain computations to INDOT Hydraulics for review?

  Please send all median drain reports, plans and computations to the office of hydraulics for review.  Reference to the INDOT Hydraulics presentation on median drains is recommended.

• For projects with multiple structure types (e.g. bridge, culvert, detention), what is the proper way to submit the projects?

  The proper way to submit projects with multiple types is to separate the types by category in a limited fashion. For example culverts will be their own submittal as well as detention in its own and storm sewers in its own.  Culvert submittals should be limited to ten structures.

• How do I open the zipped files uploaded to ERMS?

  The zip files can be opened using a free software called 7-zip and can be downloaded via the website https://www.7-zip.org/download.html.  It is recommended to use the most up to date version.

• When do I consider needing to sump a structure?

  Three-sided structures, spill through structures, storm drain systems, and structures with inlet depressions should not be sumped. For other culverts, sumping is required unless the Waters Report determined the location not to be a Waters of the US nor Waters of the State.

Contact Information

Mark Bailey
Director of Hydraulics
Indiana Department of Transportation
100 N. Senate Ave., N758 - Hydraulics
Indianapolis, IN 46204
317-233-2096
MBailey1@indot.in.gov

Hydraulics@indot.IN.gov

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