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Publication Number:  FHWA-HRT-14-064    Date:  August 2014
Publication Number: FHWA-HRT-14-064
Date: August 2014


Fish Passage in Large Culverts With Low Flow

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The study described in this report was conducted at the Federal Highway Administration's Turner-Fairbank Highway Research Center (TFHRC) J. Sterling Jones Hydraulics Laboratory in response to the need for guidance to evaluate the variation of velocity within a culvert cross-section to facilitate fish passage design identified by State transportation departments. The State transportation departments that contributed funding for the realization of this study were Alaska, Georgia, Maryland, Michigan, Minnesota, Vermont, and Wisconsin. A 3-ft corrugated metal pipe (CMP) was used during the physical modeling phase of the research study.  The results obtained from the physical modeling phase of the study were corroborated during the computational fluid dynamics numerical modeling phase of the study.  This report will be of interest to hydraulic engineers and environmental scientists involved in the design of new or retrofit of existing CMPs for fish passage. The report is being distributed as an electronic document through the TFHRC Web site at https://www.fhwa.dot.gov/research/.

Jorge E. Pagán-Ortiz
Director, Office of Infrastructure
Research and Development


This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

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Technical Report Documentation Page

1. Report No.


2. Government Accession No. 3 Recipient's Catalog No.
4. Title and Subtitle

Fish Passage in Large Culverts with Low Flows

5. Report Date

August 2014

6. Performing Organization Code
7. Author(s)

Yuan Zhai, Amin Mohebbi, Roger Kilgore, Zhaoding Xie, and Jerry Shen

8. Performing Organization Report No.


9. Performing Organization Name and Address

2 Eaton Street, Suite 603
Hampton, VA 23669

10. Work Unit No. (TRAIS)

11. Contract or Grant No.
12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296

13. Type of Report and Period Covered

Laboratory Report
October 2010–December 2013

14. Sponsoring Agency Code


15. Supplementary Notes
The Contracting Officer's Representative (COR) was Kornel Kerenyi (HRDI-50). Steven Lottes and Cezary Bojanowski of the Argonne National Laboratory and Dr. Fred Chang contributed to this research. The Maryland State Highway Administration was the lead State coordinating with FHWA on this research.
16. Abstract

A series of physical and numerical modeling runs were completed to support the development of a design procedure for characterizing the variation in velocity within non-embedded and embedded culverts. Physical modeling of symmetrical half-section circular culverts was conducted to provide data against which computational fluid dynamics (CFD) modeling could be validated. The initial CFD modeling featured two-phase numerical computations that successfully reproduced the physical modeling results. To further simplify, single-phase modeling and truncated single-phase modeling were evaluated with good results. For the embedded culvert runs, a successful strategy for representing natural bed material within the culvert was developed.


Once the CFD modeling was validated by the physical modeling, the CFD modeling was used to analyze the full culvert cross-sections. Test matrices included CFD runs scaled up to larger culvert sizes. One series of runs maintained Froude number based scaling and one series tested larger sizes without the scaling constraint. The CFD runs and a velocity distribution model formed the basis of a proposed design methodology for determining the velocity distribution within a culvert cross-section. Using the 42 CFD runs for a 3-ft diameter culvert, the 5 parameters necessary for the velocity model were estimated. Then, based on geometric and hydraulic parameters available to a designer, relations were developed to estimate those parameters. The approach was successfully validated on CFD runs for 6-ft and 8-ft diameter culvert models. The proposed design procedure allows a designer to estimate the velocity throughout a cross-section. These data may be depth-averaged to provide a distribution of velocity and depth across the culvert cross-section that may be used to evaluate fish passage. Although developed for circular culverts, the parameters used in the method are such that the procedure should be applicable to rectangular and other shapes. Two design examples and an application guide are provided to illustrate the method and the required computations.

17. Key Words

culvert hydraulics, fish passage, velocity distribution, CFD, culvert embedment

18. Distribution Statement

No restrictions. This document is available to the public through NTIS:
National Technical Information Service
5301 Shawnee Road
Alexandria, VA 22312

19. Security Classification
(of this report)


20. Security Classification
(of this page)


21. No. of Pages


22. Price
Form DOT F 1700.7 Reproduction of completed page authorized


SI* (Modern Metric) Conversion Factors









ACross-section flow area, ft2 (m2)
ADVAcoustic Doppler velocimetry
ApSurface area of the wetted perimeter (culvert wall and bed), ft2 (m2)
ayVariable dependent on embedment
BiTransverse distance on the water surface to the left (i = 1) and right (i =2), ft (m)
BavgAverage flow width in the cross-section (half section), ft (m)
CADComputer-aided design
CCDCharge coupled device
CFDComputational fluid dynamics
CMPCorrugated metal pipe
CBCConcrete box culvert
CSPCorrugated structural plate
deEmbedment depth, ft (m)
DCulvert diameter, ft (m)
D50Median grain size, ft (m)
FHWAFederal Highway Administration
FrFroude number based on average cross-section velocity and depth (Va/(gya)0.5)
gGravitational acceleration, ft/s2 (m/s2)
HEC-RASHydrologic Engineering Centers River Analysis System
MVelocity distribution parameter
nManning's roughness
pPressure on the flow field at the end of the control volume, lb/ft2 (N/m2)
ΔpChange in pressure from one end of the control volume to the other, lb/ft2 (N/m2)
PbWetted perimeter for the bed material, ft (m)
PIVParticle image velocimetry
PwWetted perimeter for the culvert wall, ft (m)
QCulvert discharge, ft3/s (m3/s)
QHHigh passage discharge, ft3/s (m3/s)
QLLow passage discharge, ft3/s (m3/s)
RANSReynolds-averaged Navier-Stokes
ReReynolds number based on hydraulic radius (VaRh/v)
RhHydraulic radius, ft (m)
RMSRoot mean square
RMSERoot mean square error
SPIVStereoscopic particle image velocimetry
TTop width of the water surface, ft (m)
u*Mean shear velocity, ft/s (m/s)
VPoint velocity, ft/s (m/s)
VaAverage flow velocity, ft/s (m/s)
VfMaximum allowable fish passage velocity, ft/s (m/s)
ViDepth average velocity of the ith cross-section slice, ft/s (m/s)
VmaxMaximum flow velocity in a cross-section, ft/s (m)
VOFVolume of fluid
yVertical distance from the lowest elevation of the flow field, ft (m)
YNormalized Cartesian coordinate in the vertical direction
yaAverage flow depth (A/T), ft (m)
yfMinimum required depth for fish passage, ft (m)
yiFlow depth of the ith cross-section slice, ft (m)
ymaxMaximum flow depth, ft (m)
zHorizontal distance from the culvert centerline, ft (m)
ZNormalized Cartesian coordinate in the horizontal direction
βiVelocity distribution parameter
δiVelocity distribution parameter, ft (m)
δyVelocity distribution parameter, ft (m)
εVelocity distribution parameter, ft (m)
ηCoordinate axis in the ξ-η system
vKinematic viscosity, ft2/s (m2/s)
τwWetted perimeter shear stress, lb/ft2 (N/m2)
ξCoordinate axis in the ξ-η system
ξ0Minimum value for the ξ coordinate
ξmaxMaximum value for the ξ coordinate


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