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Bridges & Structures

HY-8 Culvert Hydraulic Analysis Program

HY-8 automates culvert hydraulic computations utilizing a number of essential features that make culvert analysis and design easier. An HY-8 User Manual is included with the software installation (access via 'Help' button on top toolbar) to provide important information on the technical features, capabilities, and limitations of the software.

System Compatibility

HY-8 is a 32-bit program, but it is fully compatible with 32 and 64-bit Windows-based operating systems (XP, Vista, Windows 7, and Windows 10) and runs in 32-bit mode on these operating systems. When installing HY-8, make sure you have permissions on your computer to install programs (usually this requires administrator permissions or a username and password for an administrator account). If you do not have administrator permissions on your account, you need to right-click on the installation program and select the "Run as Administrator" option if running Windows Vista or Windows 7. Windows XP users should login to an account that allows you to install software before installing HY-8.

Download Agreement

By downloading the software, users acknowledge that they have read and agree to the following conditions:

  • The application of this software is the responsibility of the user. It is imperative that the responsible designer understands the potential accuracy limitations of the program results, independently cross checks those results with other methods, and examines the reasonableness of the results with engineering knowledge and experience.
  • There are no expressed or implied warranties.

I agree to these conditions, download the software:

HY-8 Version 7.60

  • Build Date July 30, 2019. This version does not include new features, but rather: 1) corrects computational issues with embedded circular culverts, 2) fixes many reported bugs, 3) improves computational stability, and 4) updates the user interface. The HY-8 User’s Manual included with the software package (available by selecting “HY-8 Help” in the “Help” drop-down menu) describes the corrections to the embedded circular culvert logic in Section 4.1, Embedment Depth. Please email Eric Brown (eric.r.brown@dot.gov) if you want additional details on the implemented corrections to embedded circular culverts and a complete list of maintenance items implemented in Version 7.60.

HY-8 Version 7.50

  • Build Date July 28, 2016. This version contains two new calculators: a) a calculator to assist with the FHWA's culvert aquatic organism passage (AOP) design procedure, which is described in detail within Hydraulic Engineering Circular 26, "Culvert Design for Aquatic Organism Passage, First Edition" (HEC-26), and b) a calculator to determine the variation in cross-sectional flow velocity from the culvert wall to the centerline, which is described within Research Publication No. FHWA-HRT-14-064, "Fish Passage in Large Culverts with Low Flows".

    Improvements made to this version of the software include: corrections to the AOP calculator, a correction to the calculation of roadway overtopping for various scenarios, a correction to the calculation of composite Manning's n values for user defined shapes, edits to the Saint Anthony Falls (SAF) Energy Dissipator routine, and edits to the Riprap Basin Dissipator routine.

Reporting Issues

If you believe you have found an issue with any version of HY-8 (including installation errors, calculation errors, interface problems, confusing functions, errors and omissions in the User Manual, and anything else that might impact the functionality and usability of the software), please submit the following information to CommentsOnHY8@dot.gov (please note that in most cases you will not receive a personalized email response from the email administrator):

  • Name
  • Contact info (this won't be used unless there is a question about your HY-8 issue)
  • Computer operating system (Windows 8, Windows Vista, etc.)
  • Complete description of each issue
  • PLEASE attach the HY-8 project file (.hy8) that demonstrates the issue
  • Also consider attaching a screen shot of the HY-8 window if applicable
Updated: 09/23/2019
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000