Hydraulics of Minimum Energy Loss (MEL) culverts and bridge waterways
by Hubert CHANSON (h.chanson@uq.edu.au)
M.E., ENSHM Grenoble, INSTN, PhD (Cant.), DEng (Qld), Eur.Ing., MIEAust., MIAHR, 13th Arthur Ippen awardee
 Dept. of Civil Engrg., Univ. of Queensland, Brisbane QLD 4072, Autralia
Detailed photographs
Historical developments
About the author

A culvert is a covered channel of relatively short length designed to pass water through an embankment (e.g. highway, railroad, dam). It is a hydraulic structure and it may carry flood waters, drainage flows, natural streams below earthfill and rockfill structures. The design can vary from a simple geometry (i.e. box culvert) to a hydraulically-smooth shape : i.e., the Minimum Energy Loss (MEL) design.

In the coastal plains of Queensland (North-East of Australia), torrential rains during the wet season place a heavy demand on culverts. Further the natural slope of the flood plains is often very small (So ~ 0.001) and little fall (or head loss) is permissible in the culverts. Professors G.R. McKAY and C.J. APELT developed and patented the design procedure of minimum energy loss waterways. Professor C.J. APELT presented an authoritative review of the topic (APELT 1983) and a well-documented documentary (APELT 1994).

A Minimum Energy Loss culvert or waterway is a structure designed with the concept of minimum head loss. The flow in the approach channel is contracted through a streamlined inlet into the barrel where the channel width is minimum, and than it is expanded in a streamlined outlet before being finally released into the downstream natural channel. Both the inlet and outlet must be streamlined to avoid significant form losses. The barrel invert is often lowered to increase the discharge capacity (see Photographs). APELT (1983) presented an authoritative review of the topic. CHANSON discussed the wide range of design options (CHANSON 2000) and he showed detailed illustrations (CHANSON 1999, pp. 363-368, 383-397, & 421-430).

Basic design concepts
The basic concepts of MEL culvert design are : streamlining and critical flow conditions throughout all the waterway (inlet, barrel, outlet) (APELT 1983, CHANSON 1999,2000).

Streamlining : The intake is designed with a smooth contraction into the barrel while the outlet, also called diffuser, is shaped as a smooth expansion back to the natural channel. The 'smooth' shapes should reduce the head losses (compared with a standard culvert) for the same discharge and barrel width. Practically small head losses are achieved by streamlining the inlet and outlet forms : i.e., the flow streamlines will follow very smooth curves and no separation is observed (1).

Critical flow conditions : In an open channel, maximum discharge per unit width for a given specific energy is achieved at critical flow conditions. Minimum Energy Loss structures are designed to achieve critical flow conditions IN ALL THE ENGINEERED WATER WATERWAY. That is, in the inlet, at the throat (or barrel) and in the outlet. At the throat, the discharge per unit width q may be increased by lowering the barrel bed while satisfying the Bernoulli principle (2).

Historical developments
The concept of Minimum Energy Loss culverts was developed by Norman COTTMAN, shire engineer in Victoria (Australia) and by Professor Gordon McKAY, University of Queensland (Brisbane, Australia) during the late 1960s (CHANSON 2003). While a number of small-size structures were designed and built in Victoria, some major structures were designed, tested and built in South-East Queensland.
The largest Minimum Energy Loss waterway is the Nudgee Road MEL waterway near the Brisbane airport with a design discharge capacity of 800 m3/s. Built between 1968 and 1970, the waterway design tested in laboratory with a 1:48 scale model. Since completion, the structure passed successfully floods and it is still in use. An unusual construction feature is the grass-lined channel bed. Several Minimum Energy Loss culverts were built in Southern Brisbane during the construction of the South-East Freeway, along Norman Creek in 1974-1975. The design discharge capacity range from 200 to 250 m3/s. All the structures are still in use today (Photographs 1,2, 4 & 5). A MEL culvert (Qdes = 60 m3/s) was built at Jerry's Downfall in southern Brisbane in 1970. (The structure no longer exists).
McKAY (1971) indicated further MEL culverts built in Northern Territory near Alice springs in 1970.

(1) The shape of the standard and MEL culverts can be respectively compared to a sharp-edge orifice and a Venturi-meter in a circular pipe. At an orifice, large head losses take place in the recirculation region immediately downstream of the orifice as for a standard culvert. In the Venturi-meter, the flow is streamlined and very small head losses are observed. From a top view, the MEL culvert sidewalls follow usually the shape of a Venturi meter. As for a Venturi meter, the angle between straight diverging walls and the waterway centreline should be less than about 8 degrees (for straight wing wall outlets).
The inlet and outlet may be designed using a flow net analysis and the "potential flow theory" (e.g. VALLENTINE 1969). The contour lines (i.e. lines of constant invert elevation) are the equi-potentials which must be perpendicular to the streamlines everywhere.The wingwalls are streamlines and the complete flow net may be drawn by test and trial (e.g. VALLENTINE 1969, pp. 77-87).
(2) At critical flow conditions, the culvert barrel invert excavation yields an increase in specific energy according to the Bernoulli principle (CHANSON 1999,2004). The associated increase in critcial flow depth (Emin = 2/3*dc) induces an increase in flow rate per unit width : q = sqrt(g*dc3).

Detailed photographs

Photo No. 1 : Inlet of a MEL culvert along Norman Creek underneath Ridge Street, Brisbane (QLD, Australia). Note the handrail along the bicycle/footpath passing in one cell. MEL culvert No. MEL-C-3 (CHANSON 1999, pp. 421-430). Design discharge : 220 m3/s, 7 cells of 2-m width each. View of the inlet during a field trip with students in Aug. 2000. Culvert outlet during field trip with students in Aug. 2001 (Courtesy of Mr A.K. ABDULLAH SANI). Outlet viewed from downstream on 13 May 2002 (Courtesy of C. HINTON). Inlet operation and Outlet operation on 31 Dec. 2001 after a rainstorm (Q ~ 60-70 m3/s). Approach flood plain , Inlet and Downstream flood plain during CIVL4510 student survey on 13 May 2002. Outlet during CIVL3140 field trip on 5 Sept. 2007 : Photo 1 & Photo 2. CIVL3140 student field trip on 9 Sept. 2009: students walking in the outlet with the low-flow drain in the foreground.

Photo No. 2 : Outlet and barrel of a MEL waterway along Norman Creek, under the South-East freeway and parallel to Ridge St (Brisbane QLD, Australia). Looking upstream. MEL waterway No. MEL-W-1 (CHANSON 1999, pp. 421-430). Design discharge : 200 m3/s, Barrel width : 10 m. Outlet operation (view from downstream) on 31 Dec. 2001 after a rainstorm (Q ~ 60-70 m3/s). Field trip by CIVL4510 students (where are they?) on 13 May 2002. CIVL3140 student field trip on 9 Sept. 2009: student group in front of the inlet.

Photo No. 3 : Outlet of the MEL culvert at Redcliffe (QLD, Australia) between the shopping centre and the sea. View of the outlet looking at the Moreton Bay. MEL culvert No. MEL-C-6 (CHANSON 1999, pp. 421-430). Design discharge : 36 m3/s, Barrel width : 5.5 m, Barrel length : 137 m, Invert drop : 1.2 m.

Photo No. 4 : MEL culvert No. MEL-C-2 (CHANSON 1999, pp. 421-430). Design discharge : 220 m3/s. Located along Norman Creek underneath SE Freeway parallel to Birdwood St, Brisbane (Australia). Inlet, looking from the left bank on 13 May 2002.

Photo No. 5 : MEL culvert No. MEL-C-X2 (CHANSON 2004), Ekibin Park, on Norman Creek. Design discharge : 220 m3/s. Built in 1971. Located underneath South-East Freeway. Inlet survey during Field survey CIVL4510 on Mon 13 May 2002. CIVL3140 student field trip on 9 Sept. 2009: Inlet of the MEL culvert, looking upstream; Outlet of of the MEl culvert.

Photo No. 6 : MEL culvert No. MEL-C-4 (CHANSON 1999). Design discharge : ~220 m3/s. MEL culvert beneath the Gateway motorway (Brisbane, Australia). Photo No. 6a : inlet on 11 Sept. 2002 during CIVL3140 student field trip. Photo No. 6b : inlet wingwall on 11 Sept. 2002 during CIVL3140 student field trip.

Photo No. 7 : MEL culvert No. MEL-C-5 (CHANSON 1999). Design discharge : ~100 m3/s. MEL culvert beneath the Gateway motorway (Brisbane, Australia). Photo No. 7a : inlet on 11 Sept. 2002 during CIVL3140 student field trip. Photo No. 7b : students in inlet channel on 11 Sept. 2002 during CIVL3140 student field trip. Photo No. 7c : students at the dowsntream end of the barrel on 11 Sept. 2002 during CIVL3140 student field trip.

Photo No. 8: CIVL3140 students in a MEL culvert barrel on 19 April 2016.
Photo No. 10: MEL culvert outlet on 19 April 2016 during CIVL3140 field trip.

Norman Creek flood flow on 7 November 2004
Photographs No. 21 to 27 : Flood flow (80-100 m3/s) after 60-150 mm of rainfall in less than 3 hours. Photo No. 20: outlet of the Ridge St MEL culvert (MEL-C-3) on 7 Nov. 2004, looking upstream; Photo No. 22: inlet operation, looking downstream (Ridge St MEL culvert (MEL-C-3) on 7 Nov. 2004); Photo No. 23: inlet operation, looking upstream from the culvert embanment (Ridge St MEL culvert (MEL-C-3) on 7 Nov. 2004); note the MEL waterway No. MEL-W-1 in background; Photo No. 24: MEL water MEL-W-1 barrel in operation on 7 Nov. 2004, looking downstream; note the standing wave flow; Photo No. 25: inlet operation, view from right bank (MEL waterway (MEL-W-1) on 7 Nov. 2004); Photo No. 26: outlet operation, looking upstream (MEL waterway (MEL-W-1) on 7 Nov. 2004); Photo No. 27: creek operation between Ridge St and Juliette St on 7 nov. 2004, flow from right to left; note supercritical flow beneath the bicycle bridge, and shock waves downstream of the bridge.

Norman Creek field survey on 11 April 2005

Group 1 : students surveying the Birdwood St MEL culvert inlet, looking upstream from the barrel. Group 2 : student discussion in the Ekibin MEL culvert inlet. Group 3 : survey preparation, downstream of the Ekibin MEL culvert outlet. Group 4 : field work preparation. Group 5 : survey of the MEL waterway beneath the SE freeway. Group 6 : survey of the Ridge St MEL culvert inlet. Group 8 : flood plain survey downstream of Juliette St. Group 9 : student survey of Cornwall St culvert.

Norman Creek floods on 20 May 2009
Culvert operation during the floods on 20 May 2009: Photo No.1: inlet operation around 09:10. Photo No.2: inlet operation at 11:00; note the larger flow rate through the culvert and the hydraulic jump roller in the foreground.


   APELT, C.J. (1983). "Hydraulics of Minimum Energy Culverts and Bridge Waterways." Australian Civil Engrg Trans., I.E.Aust., Vol. CE25, No. 2, pp. 89-95 (ISSN 0819-0259). (PDF file at UQeSpace) (Download PDF file)
   APELT, C.J. (1994). "The Minimum Energy Loss Culvert." Videocassette VHS colour, Dept. of Civil Eng., University of Queensland, Australia, 18 minutes. [Library call number: TE213 .M56 2010] (UQ Library Holding)
   CHANSON, H. (1999). "The Hydraulics of Open Channel Flow : An Introduction." Butterworth-Heinemann, London, UK, 512 pages (ISBN 0 340 74067 1).
   CHANSON, H. (2000). "Introducing Originality and Innovation in Engineering Teaching: the Hydraulic Design of Culverts." European Journal of Engineering Education, Vol. 25, No. 4, pp. 377-391 (ISSN 0304-3797). (PDF file at UQeSpace)  (Download PDF File)
   CHANSON, H. (2003). "History of Minimum Energy Loss Weirs and Culverts. 1960-2002." Proc. 30th IAHR Biennial Congress, Thessaloniki, Greece, J. GANOULIS and P. PRINOS Ed., Vol. E, pp. 379-387 (ISBN 960-243-599-2).(PDF file at UQeSpace) (Download PDF File)
   CHANSON, H. (2003). "Minimum Energy Loss Structures in Australia : Historical Development and Experience." Proc. 12th Nat. Eng. Heritage Conf., IEAust., Toowoomba Qld, Australia, N. Sheridan Ed., pp. 22-28 (ISBN 0-646-42775-X). (PDF file at UQeSpace) (Download PDF File)
   CHANSON, H. (2004). "Développement et Expérience avec les Systèmes de Drainage à Pertes de Charge Minimales (Minimum Energy Loss Culverts)." ('Development and Experience with Minimum Energy Loss Culverts.') Jl La Houille Blanche, No. 6, pp. 120-129  (ISSN 0018-6368) (in French). (PDF file at UQeSpace) (Download PDF file)
   CHANSON, H. (2004). "The Hydraulics of Open Channel Flow : An Introduction." Butterworth-Heinemann, 2nd edition, Oxford, UK, 630 pages (ISBN 0 7506 5978 5).
   CHANSON, H. (2006). "Minimum Specific Energy and Critical Flow Conditions in Open Channels." Journal of Irrigation and Drainage Engineering., ASCE, Vol. 132, No. 5, pp. 498-502 (ISSN 0733-9437). (PDF file) (PDF file at UQeSpace)
   CHANSON, H. (2007). "Hydraulic Performances of Minimum Energy Loss Culverts in Australia." Journal of Performances of Constructed Facilities, ASCE, Vol. 21, No. 4, pp. 264-272 (ISSN 0887-3828). (PDF file) (Record at UQeSpace)
   McKAY, G.R. (1971). "Design of Minimum Energy Culverts." Research Report, Dept of Civil Eng., Univ. of Queensland, Brisbane, Australia, 29 pages & 7 plates. (PDF file at UQeSpace)
   McKAY, G.R. (1978). "Design Principles of Minimum Energy Waterways." Proc. Workshop on Minimum Energy Design of Culvert and Bridge Waterways, Australian Road Research Board, Melbourne, Australia, Session 1, pp. 1-39. [Library call number: TE213 .W67 1978]
   VALLENTINE, H.R. (1969). "Applied Hydrodynamics." Butterworths, London, UK, SI edition.


Video movies at UQeSpace
   CHANSON, H. (2020). "Hydraulics of open channel flow: practical experiments at the University of Queensland, Australia." Collection, Generic Document, The University of Queensland, School of Civil Engineering, Brisbane, Australia (ISBN 978-1-74272-311-2). {https://espace.library.uq.edu.au/collection/UQ:734960}

    EDLIN, S., LU, Z., and CHANSON, H. (2020). "The Broad-Crested Weir." Generic Document, The University of Queensland, School of Civil Engineering, Brisbane, Australia (ISBN 978-1-74272-311-2). {https://espace.library.uq.edu.au/view/UQ:734961}
    SHI, S., ASTORGA MOAR, A., and CHANSON, H. (2020). "The Hydraulic Jump." Generic Document, The University of Queensland, School of Civil Engineering, Brisbane, Australia (ISBN 978-1-74272-311-2). {https://espace.library.uq.edu.au/view/UQ:734962}
    LI, Y., LANCASTER, O., and CHANSON, H. (2020). "Backwater in a Long Channel." Generic Document, The University of Queensland, School of Civil Engineering, Brisbane, Australia (ISBN 978-1-74272-311-2). {https://espace.library.uq.edu.au/view/UQ:734963}
    WUTHRICH, D., WUPPUKONDUR, A., and CHANSON, H. (2020). "Hydraulics of Culverts." Generic Document, The University of Queensland, School of Civil Engineering, Brisbane, Australia (ISBN 978-1-74272-311-2). {https://espace.library.uq.edu.au/view/UQ:734964}

Related links

UQ subject CIVL3140 Introduction of Open Channel Flow
Gallery of photographs in hydraulic engineering and environmental fluid mechanics
{http://staff.civil.uq.edu.au/h.chanson/photo.html#Culverts} Photographs of culvert structures including culvert operations
{http://staff.civil.uq.edu.au/h.chanson/mel_culv.html} Upstream fish passage in box culverts: how do fish and turbulence interplay?
{http://www.civil.uq.edu.au/icarus/fish-passage-culverts-hydrodynamic-investigation} 2016 Icarus project on Fish passage in culverts: hydrodynamic investigation



The writer acknowledges the advice of and discussions with Emeritus Professor Colin APELT (The University of Queensland).


Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License.

Hubert CHANSON is a Professor in Civil Engineering, Hydraulic Engineering and Environmental Fluid Mechanics at the University of Queensland, Australia. His research interests include design of hydraulic structures, experimental investigations of two-phase flows, applied hydrodynamics, hydraulic engineering, water quality modelling, environmental fluid mechanics, estuarine processes and natural resources. He has been an active consultant for both governmental agencies and private organisations. His publication record includes over 1200 international refereed papers and his work was cited over 6,500 times (WoS) to 22,500 times (Google Scholar) since 1990. His h-index is 43 (WoS), 47 (Scopus) and 76 (Google Scholar), and he is ranked among the 150 most cited researchers in civil engineering in Shanghai’s Global Ranking of Academics. Hubert Chanson is the author of twenty books, including "Hydraulic Design of Stepped Cascades, Channels, Weirs and Spillways" (Pergamon, 1995), "Air Bubble Entrainment in Free-Surface Turbulent Shear Flows" (Academic Press, 1997), "The Hydraulics of Open Channel Flow: An Introduction" (Butterworth-Heinemann, 1st edition 1999, 2nd editon 2004), "The Hydraulics of Stepped Chutes and Spillways" (Balkema, 2001), "Environmental Hydraulics of Open Channel Flows" (Butterworth-Heinemann, 2004), "Tidal Bores, Aegir, Eagre, Mascaret, Pororoca: Theory And Observations" (World Scientific, 2011), "Applied Hydrodynamics: an Introduction" (CRC Press, 2014). He co-authored three further books "Fluid Mechanics for Ecologists" (IPC Press, 2002), "Fluid Mechanics for Ecologists. Student Edition" (IPC, 2006) and "Fish Swimming in Turbulent Waters. Hydraulics Guidelines to assist Upstream Fish Passage in Box Culverts" (CRC Press 2021). His textbook "The Hydraulics of Open Channel Flows: An Introduction" has already been translated into Spanish (McGraw-Hill Interamericana) and Chinese (Hydrology Bureau of Yellow River Conservancy Committee), and the second edition was published in 2004. In 2003, the IAHR presented him with the 13th Arthur Ippen Award for outstanding achievements in hydraulic engineering. The American Society of Civil Engineers, Environmental and Water Resources Institute (ASCE-EWRI) presented him with the 2004 award for the Best Practice paper in the Journal of Irrigation and Drainage Engineering ("Energy Dissipation and Air Entrainment in Stepped Storm Waterway" by Chanson and Toombes 2002), the 2018 Honorable Mention Paper Award for  "Minimum Specific Energy and Transcritical Flow in Unsteady Open-Channel Flow" by Castro-Orgaz and Chanson (2016) in the ASCE Journal of Irrigation and Drainage Engineering, and the 2020 Outstanding Reviewer Award. The Institution of Civil Engineers (UK) presented him the 2018 Baker Medal. In 2018, he was inducted a Fellow of the Australasian Fluid Mechanics Society. Hubert Chanson edited further several books : "Fluvial, Environmental and Coastal Developments in Hydraulic Engineering" (Mossa, Yasuda & Chanson 2004, Balkema), "Hydraulics. The Next Wave" (Chanson & Macintosh 2004, Engineers Australia), "Hydraulic Structures: a Challenge to Engineers and Researchers" (Matos & Chanson 2006, The University of Queensland), "Experiences and Challenges in Sewers: Measurements and Hydrodynamics" (Larrate & Chanson 2008, The University of Queensland), "Hydraulic Structures: Useful Water Harvesting Systems or Relics?" (Janssen & Chanson 2010, The University of Queensland), "Balance and Uncertainty: Water in a Changing World" (Valentine et al. 2011, Engineers Australia), "Hydraulic Structures and Society – Engineering Challenges and Extremes" (Chanson and Toombes 2014, University of Queensland), "Energy Dissipation in Hydraulic Structures" (Chanson 2015, IAHR Monograph, CRC Press). He chaired the Organisation of the 34th IAHR World Congress held in Brisbane, Australia between 26 June and 1 July 2011. He chaired the Scientific Committee of the 5th IAHR International Symposium on Hydraulic Structures held in Brisbane in June 2014. He co-chaired the Organisation of the 22nd Australasian Fluid Mechanics Conference held as a hybrid format in Brisbane, Australia on 6-10 December 2020.
 His Internet home page is http://www.uq.edu.au/~e2hchans. He also developed a gallery of photographs website {http://www.uq.edu.au/~e2hchans/photo.html} that received more than 2,000 hits per month since inception.

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  Energy Dissipation in Hydraulic StructuresApplied Hydrodynamics Tidal boresApplied HydrodynamicsEnvironmental hydraulics of open channel flowHydraulics of open channel flow (2nd edition)The Hydraulics of Stepped Chutes and SpillwaysThe Hydraulics of Open Channel Flow: an IntroductionAir bubble entrainment in turbulent shear flowsHydraulic design of stepped cascades, channels, weirs and spillways  McGraw-Hill Interamericana 13th Ippen award (IAHR)