Presentation
The Gold Creek dam was designed by John HENDERSON (1836-1916) for the Brisbane Board of Waterworks (WHITMORE 1996, COSSINS 2000). The purpose of the dam was to increase the water supply for the city of Brisbane. The dam built between 1882 and 1885 is an earthfill embankment with a clay puddle corewall . It was built under the general supervision of HENDERSON and the site engineer was Alexander STEWART (1843-1900).  The length of the dam is 187-m (624 ft) and the maximum height of the embankment is 26-m (86 ft). The reservoir storage capacity is about 1.8 10+6 m3. The catchment area is 10.48 km2 of protected forest area.
An overflow spillway is located on the left abutment on rock foundation. An outlet tower was built between 1883 and 1885 to draw water from the reservoir. The original structure in cast iron failed in 1904, following improper operation while the reservoir was empty. The structure was replaced by the present concrete structure built in 1905.
Originally, the Gold Creek reservoir supplied water directly to the city. In 1928, the reservoir was connected to Enoggera reservoir via a tunnel beneath the ridge separating Enoggera Creek and Gold Creek basins. The Gold Creek dam acted as an upper reservoir for the Enoggera reservoir as the Gold Creek reservoir is located close to and at a higher elevation than the Enoggera dam. Nowadays the Gold Creek reservoir is no longer in use, the pipeline having been decommissioned in 1991. The reservoir is managed by Brisbane Forest Park, and it was kept nearly full until early 2004 when the water level was artifically lowered for dam safety.

The spillway system
The Gold Creek catchment area and the neighboring Enoggera Creek basin can be subjected to very intense rainfalls : e.g., 920 mm during a storm on 24 January 1974. Since dam construction, the spillway has been modified four times essentially, each time to increase the discharge capacity (CHANSON and WHITMORE 1998).
The original 1885 spillway was a crude channel cut in the left abutment. In 1887, the spillway channel was widened by 15 m. In January 1887 and March 1890, large overflows occurred and the unlined rock spillway was badly damaged (CHANSON and WHITMORE 1996). As a result it was decided to build a masonry spillway in 1890. The design was approved by J. HENDERSON  and the drawing of the spillway was signed by A. STEWART. It is believed that the contractors for the spillway were COWLEY and ANNEAR. The 1890 spillway was a staircase structure made of concrete, the concrete aggregate being obtained from the original spillway rock material . The final staircase structure had twelve steps (1.5 m high) although some original drawings showed originally 19 steps. In 1920, a low concrete wall was built across the spillway crest to increase the reservoir capacity. It was dismantled in 1932 (WHITMORE 1996). In 1975, the level of the spillway crest was lowered by 1.2-m (4 feet) to increase the maximum discharge capacity  but the steep channel was unmodified. In 1998, the spillway crest was lowered by another 0.3 m. Today's spillway consists of the 1998 crest followed by the 1890 stepped channel, although a 5 m cut in the middle of the spillway crest was made in 2004 to lower the water rervoir.
The maximum discharge capacity of the 1890 spillway was probably selected to pass the maximum observed flood at the time : i.e., 170 m3/s in January 1887. The "theoretical" discharge capacity of the 1975 and 1998 spillways is much larger (360 m3/s for 1975 crest design, ~600 m3/s for 1998 crest design). But CHANSON and WHITMORE (1996,1998) showed that the maximum capacity of the stepped channel is 280 m3/s. For larger discharges, overtopping of the right sidewall would occur, causing unacceptable scouring and erosion at the embankment dam toe.

Discussion
Since Antiquity, dam engineers learned the risks of dam erosion and destruction associated with large floods, and it was usual to design dams with a spillway system. In most early dams, the waters were discharged over the dam crest or beside the dam. In ancient structures, a stepped spillway design was selected to contribute to the stability of the dam and simplicity of shape (CHANSON 2001). Later design engineers realised the advantages of stepped channels for energy dissipation purposes and to prevent scouring.
During the 19th century, overflow stepped spillways were selected frequently, with nearly one third of the dams built in USA being equipped with a stepped cascade. Most structures were masonry and concrete dams with a downstream stepped face reinforced by granite blocks (e.g. Goulburn weir). Some dams were equipped with stepped rocklined spillways : e.g., Ternay and La Tâche dams. Others had a lateral spillway (e.g. Le Pont dam). Earth embankments were usually equipped a lateral spillway (e.g. Val House dam, Gold Creek dam). The development of stepped spillway was marked by two milestones : the Gold Creek dam cascade (1890, Australia) and the New Croton dam (1906, USA). It is believed that the Gold Creek cascade was the world's first concrete stepped spillway and the ancestor of modern RCC stepped spillways (CHANSON and WHITMORE 1998). Completed in 1906, the New Croton dam spillway is probably the first stepped chute designed specifically to maximise energy dissipation. It is still in use despite a major accident in 1955 (CHANSON 2001).

The educational role of Gold Creek dam and spillway

Water supply in Australia is limited because of the dry climate. Hydraulic engineering expertise is therefore critical to the country's future developments, and most undergraduate civil and environmental engineering curricula in Australian universities include a significant hydraulics component. At the University of Queensland, hydraulics and water resource engineering are lectured in the civil and environmental engineering curricula. The lecture material is structured to guide the students from the basic principles of fluid mechanics to their application to engineering design (CHANSON 2001b). The focus is on the basic understanding of fundamental principles and their sound applications to real-world applications. In the context of undergraduate and postgraduate subjects, design applications in classroom are restricted to simple flow situations and boundary conditions for which the basic equations can be solved analytically or with simple models. Field work activities (Photo No. 3) are essential to illustrate real professional situations, and the complex interactions between all engineering and non-engineering constraints (e.g. CHANSON 2001,2004). For example, the construction of a dam and reservoir across a river involves first a study of the stream hydrology and catchment characteristics, while the design of the weir is based upon structural, geotechnical and hydraulic considerations. A consequent cost of the structure is off course the spillway, designed to pass safely the maximum peak flood. In addition the impact of the weir on the upstream and downstream valleys must be considered.

Although first introduced to motivate students' interest, field studies in undergraduate hydraulic courses have been an integral part of the teaching pedagogy for more than ten years at the University of Queensland (CHANSON 2004). Gold Creek dam is one of the best field study sites for University students based in Brisbane . Photo No. 4 and Photo N. 5A show respectively E2408 Hydraulic design students and CIVL3140 Open channel flow students inspecting the Gold Creek dam and its spillway system under the expert guidance of the writer. Key features of the main spillway include a 55-m wide 60-m long broad crest, a stepped chute completed in 1890 and the absence of downstream stilling basin. During the field work, students surveyed the broad-crest, inspected the steep stepped chute and investigated the downstream energy dissipator (Photo No. 5B).

Students can become thrilled by relevant field studies directly relevant to the course material and Gold Creek dam field studies are no exception. For example, a broad-crested weir is often perceived as a "dull" structure in the classroom, but it may become a
fascinating hydraulic structure in the context of a hydraulics field work, particularly with large structures (Photo No. 5B). The students gain also first hand experience on real-world issues associated with a hydraulic structure design. At Gold Creek dam, these include road access (incl. road submergence during floods), earth embankment dam design, concrete durability (1890 concrete steps) and spillway refurbishments.

Note that the pedagogical role of the Gold Creek dam and spillway have been acknowledged in publications by the American Society for Civil Engineers (Journal of Hydraulic Engineering, Dec 2001 & Journal of Professional Issues in Engineering Education and Practice, Oct. 2004), while photographs of Gold Creek dam student field trips were published in a number of textbooks (e.g. Elsevier-Butterworh-Heinemann 2004, Balkema 2001).

Summary

In summary, a University of Queensland team lead by Hubert CHANSON has investigated the historical development of the Gold Creek dam stepped cascade and its hydraulic characteristics. The University study suggests a sound design of the dam and the cascade, a 1890 cascade design based on Australian and overseas experience (Victoria, Great Britain, France).
Unique features of the stepped spillway include the only stepped cascade built in Queensland before 1900, and the world's first use of non reinforced concrete as construction material for a stepped spillway. The stepped spillway is a superb example of Engineering Heritage considering its safe operation for more than a century and the sound cascade design by today's standards. It is the strong belief of the writer that the Gold Creek dam stepped spillway should be heritage listed, and that its international significance be recognised by local, state and federal governments in Australia.
Further the Gold Creek dam and its spillway system are unique educational and pedagogical facilties to further the education and expertise of future graduates and professionals.
 

Detailed photographs

Timber crib weirs
Whetstone weir (Inglewood QLD, Australia 1951) at low flow (H. CHANSON, Feb. 1998) - Timber crib stepped weir (H = 5 m) on the Macintyre Brook, completed in 1951. A major flood occurred in 1956, the maximum recorded stream height being 11.8 m at Inglewood.
Silverleaf weir (Murgon QLD, Australia 1953) (H. CHANSON, Nov. 1997) - Timber crib stepped weir (H = 5.1 m) on the Barambah Creek. More about Timber crib weirs ...
Cunningham weir (Texas QLD, Australia 1953) in operation (H. CHANSON, Feb. 1998) - Timber-crib stepped weir (H = 4 m) on the Dumaresq river, completed in 1954. During a major flood in 1956, the maximum recorded head-above-crest reached 7.3 m. The weir was little damaged and it is still in use. See listing in Structurae.
Greenup weir (Inglewood QLD, Australia 1958) at low flow (H. CHANSON, Feb. 1998) - Timber crib stepped weir (H = 5 m) on the Macintyre Brook, completed in 1958, upstream of Whetstone weir. More about Timber crib weirs ...

Modern stepped spillway systems
New Croton dam stepped spillway (New York NY, USA 1955). Photo No. 1 : in July 1999 (Courtesy of Mrs J. HACKER) (Ref.: CHANSON 1995, Pergamon, pp. 189-191).
Joe Sippel weir (Murgon QLD, Australia) in November 1997 (H. CHANSON) - Completed in 1984, the 6.5-m high stepped weir is used for irrigation and water regulation purposes. The structure was built of steel sheet piles and concrete slabs. It is located upstream of the Silverleaf weir.
La Grande 2 spillway (Québec,Canada) - Unlined rock stepped cascade in operation in 1983: Photo No. 1, view from downstream (Courtesy of Michel Lefebvre) - Photo No. 2 : view of the upstream steps (Courtesy of Michel Lefebvre).
Melton dam overflow stepped spillway (Melton VIC, Australia 1916). The Melton dam is an earthfill structure. Completed in 1916, the dam was heightened twice because of the rapid reservoir siltation. During the last refurbishment in 1994, an overflow stepped spillway was added. Photo No. 1 : general view (30 Jan. 2000). Photo No. 2 : details of the dam overflow spillway (30 Jan. 2000). More about Extreme reservoir siltation ...
Riou dam (France 1990). RCC stepped spillway : h = 0.43 m. Photo No. 1 : view from downstream at sunset (photograph taken in Nov. 1994). Photo No. 2 : view from right bank (photograph taken in Nov. 1994). Photo No. 3 : view from the right bank of the crest, chute and stilling basin in June 1998. Photo No. 4 : view from downstream in June 1998. More information ...
Santa Cruz arch dam stepped spillway (New Mexico, USA). Completed in 1929, the Santa Cruz dam was a masonry arch dam. In 1987, the dam was reinforced by concrete buttresses and roller compacted concrete. A new overflow stepped spillway was built between two buttresses (Design: 56 m3/s) (Courtesy of US Bureau of Reclamation and John LABOON). More information ...
Jordan II weir (Gatton QL, Australia 1992). Reinforced-earth stepped overflow weir (H = 5.3 m). Photograph in Feb. 1998.
Brushes Clough dam spillway (1859-1991). Overflow embankment spillway system with precast concrete blocks. Photo No. 1 : General view in 1993 (Courtesy of Mr GARDINER, NWW). Photo No. 2 : details of the concrete blocks, showing the drainage holes (Courtesy of Mr GARDINER). More about Embankment overflow stepped spillways: earth dam spillways with precast concrete blocks...
Zaraysk dam (also called Laraisky), Russia (Courtesy of Prof. Y. PRAVDIVETS). Overflow embankment spillway made of precast concrete blocks.
Loyalty Road Flood Retarding dam spillway (Sydney NSW, Australia, 1996) - Photo No. 1 : view from the right bank (Courtesy of D.Patrick JAMES). Photo No. 2 : view from downstream (Courtesy of D.Patrick JAMES). Dam height : 30 m. RCC construction. Spillway capacity : 1,040 m3/s. Chute width : 30 m.
Bucca weir (Bucca QLD, Australia 1987) (H. CHANSON, 23 Dec. 2001). RCC irrigation weir on the Kolan river.
Neil Turner weir (Mitchell QLD, Australia 1984). 5.9 m high stepped weir on the Maranoa river. Photo No. 1 : general view in July 2001 (Courtesy of Chris PROCTOR). Photo No. 2 : detail of steps in July 2001 (Courtesy of Chris PROCTOR).
Artifical stepped cascade at Biloela (QLD, Australia). Design flow: 390 m3/s, step height: 2 m, width: 100 m. Photo No. 1 : General view shortly after construction in 2002 (Courtesy of Dr John MACINTOSH). Photo No. 2 : View of a step arrangement, from the right bank (Courtesy of Dr John MACINTOSH). Photo No. 3 :  1:16 scale model, based upon a Froude similitude (Courtesy of Dr John MACINTOSH). Photo No. 4 : physical model in operation for Q = 10 L/s (20 m3/s prototype); all the water flows as seepage; the colours are paint sprayed on the rockfill to visualise erosion and scour. Photo No. 5 : physical model in operation for Q = 103 L/s (210 m3/s prototype); note overflows and seepage, and the hydraulic jump downstream of the plunge point.

Stepped storm waterway systems
Storm waterway at Miya-jima (Japan) - Photo No. 1 : storm waterway below below Senjò-kaku wooden hall on 19 Nov. 2001. The stepped chute is steep (slope > 45 deg., h ~ 0.4 m). The Senjò-kaku wooden hall was built by Kyomori (AD 1168) and left unfinished at his death. It is likely that the waterway design dates from the 12th century.
Stepped road gutter systems : another application of the stepped chute design. Photo No. 1 : steep gutter along the Western freeway, Brisbane (Photograph taken in Dec. 1999). Photo No. 2 : double road gutter looking downstream, next to Sumner Rd freeway entrance, between Darra and Mt Ommaney, Brisbane (Photogaph taken in Nov. 1996).

Research onto stepped spillway hydraulics
Research on stepped spillways at UQ : 22º slope, h = 0.10 m, l = 0.25 m, W = 1 m, q = 0.103 m2/s, dc/h = 1.0. Photo No. 1 : View from upstream looking towards the inception point of air entrainment. Photo No. 2: Side view (Y90 = 0.078 m, Cmean = 0.48, Fmax = 149 Hz at the probe location) (Photographs taken on 7 July 2000). Photo No. 3 : d_c/h = 1.5 (flow from left to right, run Q23). Photo No. 4 : d_c/h = 1.1 (run Q21). Photo No. 5 : d_c/h = 0.7 (run Q22). (Download the full results as PDF files : Part 1 and Part 2)
Research on stepped spillways at UQ : 16º slope, h = 0.10 m, l = 0.35 m, W = 1 m. Photo No. 1 : Nappe flow (without hydraulic jump NA3) for dc/h = 0.64.
 

Related links

References

Acknowledgments

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 620 international refereed papers and his work was cited over 3,700 times (WoS) to 6,300 times (Google Scholar) since 1990. Hubert Chanson is the author of several books : "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), "Applied Hydrodynamics: an Introduction of Ideal and Real Fluid Flows" (CRC Press, 2009), and "Tidal Bores, Aegir, Eagre, Mascaret, Pororoca: Theory And Observations" (World Scientific, 2011). He co-authored two further books "Fluid Mechanics for Ecologists" (IPC Press, 2002) and "Fluid Mechanics for Ecologists. Student Edition" (IPC, 2006). 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). 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). He chaired the Organisation of the 34th IAHR World Congress held in Brisbane, Australia between 26 June and 1 July 2011. He chairs the Scientific Committee of the 5th IAHR International Symposium on Hydraulic Structures to be held in Brisbane in June 2014.
 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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