River Torrens

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River Torrens
View of Elder Park and Riverside Precinct from Torrens Lake.
Origin	Mount Pleasant, Mount Lofty Ranges
Mouth	Gulf Saint Vincent at Henley Beach South
Length	~85 kilometres (53 mi)
Source elevation	480 metres
Basin area	~500 km2

The River Torrens is the most significant river of the Adelaide Plains. It was one of the reasons for the siting of Adelaide, and reservoirs in its upper catchment supply a significant amount of the city's drinking water. It flows from its source in the Adelaide Hills near Mount Pleasant, across the Adelaide Plains, past the central business district and empties into Gulf St. Vincent at Henley Beach South. The upper stretches of the river and its catchment form a significant part of Adelaide’s water supply and the linear parks and lake in the lower stretch are iconic of the city.

At its 1836 discovery an inland bend was chosen as the site of Adelaide and North Adelaide. Named after Colonel Robert Torrens the river, at Adelaide, is also known its by native Kaurna name Karra wirra-parri. The river, and its tributaries, are highly variable in flow. They range from sometime raging torrents, damaging bridges and flooding city areas, to trickles or completely dry in summer. Winter and spring flooding has prompted the construction of flood reduction works. Peak flow is contained by a constructed sea outlet, landscaped linear parks and three holding reservoirs.

The rivers flora and fauna have been both deliberately and accidentally impacted since settlement. Native forests have been cleared, the rivers gravel removed for construction and many foreign species introduced. With construction of the linear parks, many species native to the river have been replanted and introduced species controlled as weeds. Since European settlement the river has been the city’s primary water source, its main sewer leading to outbreaks of typhus and cholera, and a frequently touted tourist attraction.^[1]

Contents 1 Geography and geology 1.1 Tributaries 1.2 Water flow 2 Discovery and naming 3 Changes after 1836 3.1 Flood mitigation 3.2 Torrens lake 3.3 Water use 3.4 Bridges 4 Flora and fauna 5 The river today 6 Notes 7 References 8 External links

[edit] Geography and geology

The River Torrens runs largely westward from the Adelaide hills, through the centre of Adelaide to the Gulf Saint Vincent. It originates near Mount Pleasant,close to the eastern escarpment of the Mount Lofty Ranges, approximately 480 metres above sea level. It runs predominantly along faulted north-south ground structures, which were formed during the Paleozoic era but further dislocated during the Cretaceous and earliest Tertiary. There is a 400 metre subsidence along the para fault, formed after the Pliocene, which also affects the rivers flow.^[2]

From its origin to Birdwood the river follows rolling, relatively level country before entering a hilly section that continues to Gumeracha. The river then follows sedimentary rock strata before entering a gorge after Cudlee Creek. It flows through the gorge to Athelstone, passing over the Eden fault zone of the Adelaide hills face and associated escarpment. After the scarp it flows over sedimentary rocks of varying resistance to erosion, which has lead to interspersed narrows and broad basins.^[2] From the base of the Adelaide hills to Adelaide's central business district it runs in a shallow valley with a terraced floor, then down the slope of its own alluvial fan. The structure of this fan shows that the river formerly entered Gulf Saint Vincent via the Port River. Over time the Torrens deposited sediment, choking its own outflow, then became diverted and locked behind coastal sand dunes, forming the swampy areas of the Cowandilla plains and the reedbeds.^[2]

[edit] Tributaries

The Torrens is fed by numerous seasonal creeks, which are dry for most of the year. There are five main creeks that join from the south side as it crosses the Adelaide Plains east of Adelaide, and at least five more in its path through the Adelaide Hills.^[3] The plains tributaries are prosaically named First to Fifth creeks, with First being the closest to Adelaide's city-centre and the rest numbered consecutively eastward. They flow vigorously in winter and spring but are otherwise dry, except for small flows in limited areas upstream.^[4] The creeks were originally named Greenhill, Hallett, Todd, Anstey and Ormsley rivulets respectively. "Moriatta" a Kaurna word meaning "ever flowing" is now the official name of Fourth creek. This name has been adapted to Morialta which is now the name of an electoral district, school and the Morialta Conservation Park.^[5]

First, Second and Third creeks have been particularly heavily modified and would be unrecognisable to an early settler. They have some sections converted to concrete channels, others through landscaped private gardens and are in places simply underground pipes. Much of the original vegetation has disappeared from the creeks, particularly those closest to the city. Introduced species including olives, bamboo, boxthorn, watsonia and blackberries have displaced native river species.^[6]

[edit] Water flow

When discovered by Europeans, the river was a summertime chain of waterholes bounded by large gum trees. As it flowed through the area where the city of Adelaide is sited, the river was sometimes invisible beneath its gravel stream bed. It frequently flooded in winter and did not reach the sea, instead ending at coastal dunes where its waters created a vast but shallow freshwater wetland. This wetlands, known as The Reedbeds after the dominant vegetation, occupied a large area of the western Adelaide Plains and was also fed by other waterways.^[1] The river only flowed to the sea through the Port River, Barker Inlet, and Patawalonga River following heavy rain.^[7]

The river’s catchment area of approximately 500 kilometres² is the largest of any waterway within the Adelaide region. The upper reaches are used to create a potable water supply for metropolitan Adelaide with the river supplying three of Adelaide’s eight reservoirs.^[1] The upper catchment has an average annual rainfall of between 575 millimetres, at its eastern end, to 1025 millimetres near Uraidla.^[8] The Torrens has a very variable flow, and early settlers had to use trial and error to determine bridge heights, leading to many bridges washing away.^[9] Due to the variability of Adelaide's climate, flow rates can change from a trickle to flood conditions quickly. On June 5, 1889, prior to major flooding, the flow rate before it entered the suburbs was 0.7 m³/s(cubic metres per second), rising to 129.1 m³/s, 8 days later.^[10]

What the River Torrens may be capable of performing for a week or two of the rainy season beyond sweeping down to the swamp the summer filth of Adelaide we cannot guess; but the Torrens at other times is not a river at all, but merely a chain of fresh water pools. At the present moment, its running water may be spanned with the hand and sounded with the forefinger

—The Register, 1838^[11]

Since settlement it has repeatedly flooded, sometimes with disastrous consequences. Adelaide's western suburbs were especially prone to flooding due to their location on the river's alluvial fan.^[12] As development of Adelaide progressed the amount of rainfall required for flooding decreased and consequent damage increased. Increased stormwater runoff, modification of the river's banks and other changes all served to exacerbate the problem. Work done by various groups to minimise flooding was often counter productive, where the creation of levees, moving and widening channels and other works simply shifting the flooding elsewhere.^[13]

Two early floods were, 18 September 1841 which resulted in two people drowning while trying to cross the river at Klemzig, and 22 September 1844, the largest recorded since settlement began, when "Shands brewery" was washed away after the river undermined its foundations.^[11] The 1899 flood was particularly widespread, after a year with 785.6 millimetres of rain compared to the Adelaide average of 530 millimetres, with extensive flooding of both the river and its tributaries. The river flooded market gardens and farms throughout its hills course causing extensive damage. Norwood was inundated to The Parade, Adelaide to Pirie and Rundle streets, and many areas west of the city were left in a shallow lake.^[14] The river ran 9 feet deep over the weir near Thorndon Park Reservoir, 3 feet over the Torrens Lake Weir and 1 foot over the Morphett Street bridge. The Underdale (or Holbrooks) Bridge was destroyed, the city weir's bridge damaged, and the Felixstow Bridge over the Fourth Creek washed away.^[15]

[edit] Discovery and naming

The river is dually known by the indigenous Kaurna people’s name of Karra wirra-parri (meaning river of the red gum forest), referring to the dense eucalyptus forest that lined its banks prior to clearing by early settlers. This name, alternatively karra-weera, only referred to the lake section of the river, between Adelaide and North Adelaide. It was known as karrundo-ingga at Hindmarsh , witoingga near the reed beds, and Yertala everywhere when in flood. Yertala has been translated as "water running by the side of a river" and has survived as Yatala in the naming of various places in Adelaide.^[16]

The first European sighting of the river was in November 1836 by a party of Lieutenant W.G. Field, John Morphett and George Strickland Kingston. The river was named the "Yatala" by the party^[16] but later renamed by William Light after Colonel Robert Torrens, chairman of the South Australian colonisation commissioners.^[2] On December 29, 1836 Light announced the location of the new city of Adelaide, 6 miles inland on the river's banks .^[16]

[edit] Changes after 1836

During early years of colonisation, the surrounding trees where cut down and the river’s gravel used in road making and construction of buildings. As the natural environment was removed, the banks were eroded and the riverbed gradually levelled as waterholes filled. By 1878 the river was noted to be a malodorous, black sewer rather than the sylvan stream of the 1830s.^[17]

...anything in the guise of a river more ugly than the Torrens would be impossible to either see or describe...

—Anthony Trollope prior to 1880^[18]

Much of the river's catchment area is comprised of cleared farmland with run-off captured in private dams to sustain farming over Adelaide's dry summer. Combined with the river's use for potable water this has greatly reduced the overall flow especially in the lower river.

[edit] Flood mitigation

A flood mitigation bill was passed in 1917 to not only combat the damage floods caused but also the public health risk due to the lack of mains sewerage in the western suburbs. Popular opinion was to divert the flood waters into their "natural" outlets of the Port and Patawalonga rivers. The chief engineer of the department of works favoured a cutting through sand dunes near Henley Beach, allowing the river an outlet, mitigating floods and preventing silting of the Port River. He also advocated the construction of a reservoir where the Kangaroo Creek Reservoir is now, to both mitigate floods and provide summer irrigation water for market gardens. Unfortunately the bill lapsed with no action as neither government nor local councils were willing to fund the works.^[19] The Millbrook Reservoir opened in 1918 as a summer water source, and flood mitigator if required. A bill was passed in 1923 to enact the earlier plan of cutting through the dunes and adding an upstream regulating weir. Again the bill lapsed due to a lack of commitment from parties on payment.^[20]

A major flood in 1931 and another in 1933 lead to the latest in a line of government enquiries. In 1934 the "Parliamentary standing committee on Public Works" recommended that an outlet for the river be created to accommodate flows of up to 370 m³/s(cubic metres per second) (13,000 ft³/s), covering a 1 in 60 year flood. The work was partly financed by a Commonwealth Government grant with the state government arranging for the balance. The state government, western and eastern councils and the Municipal Tramways Trust shared interest costs. The scheme was enacted in 1935 and largely completed by 1939 with the creation of "Breakout creek channel".^[21] The scheme involved diversion of the river at Lockleys (near Adelaide Airport), with the original channel blocked and a new channel created to the sea.^[1] The reedbeds and swamps were subsequently drained and some of their area is now the site for the suburb of West Lakes.

Based on recommendations in an 1925 report on flood mitigation, work began in the 1960s on the building of the Kangaroo Creek reservoir, opened in 1969 with a capacity of 24.4 megalitres^[22] It remains the only reservoir damming the river rather than being fed from weirs. The "River Torrens Committee" was formed in 1964 to advice the minister of works on; preserving and enhancing the rivers natural beauty, and developing it for recreational uses. The "River Torrens Acquisition act 1970-72" was passed authorising the purchase of land, in some cases 60 metres back from the top of the river's banks.^[23]

By 1980, further development along the riverbanks and removal of levées had reduced the outlets capacity to a 1 in 35 year flood. A study showed that a 1 in 200 year flood would inundate 13,000 properties, so the Kangaroo Creek dam's level was raised, its spillway modified, the breakout creek channel capacity increased and some bridges reinforced.^[24] A development plan was approved in 1981 to purchase land along the length of the river, create a flood mitigating linear park and also to modify the Kangaroo Creek dam further. The sea outlet was enlarged to a capacity of 410 m³/s which now covered a 1 in 200 year flood.^[25] When the O-Bahn Busway was opened the bridges were designed to cope with this scale of flood, although the two bridges in St Peters would likely be awash.^[26]

[edit] Torrens lake

The Torrens lake was created in 1881 with the construction of a weir, landscaping of Elder park and modification of the river’s bank and surrounds into an English formal park. The lake forms a centrepiece of many Adelaide events and postcard scenes. Elder park with its iron rotunda was opened on November 28, 1882. The Rotunda is an structure with ironwork made in Glasgow, and both it and the park were funded by Sir Thomas Elder Smith.^[27]

In 1867, prison labour from Adelaide Gaol was used to build a wooden dam near the site of the current weir. The dam was poorly constructed and almost immediately the Torrens washed it away. Construction of a permanent concrete weir was begun in November 1880 and completed, at a cost of 7,000 pounds, in 1881. The sluice gates were closed to begin filling the 12 hectare Torrens Lake on July 1, 1881. At the lakes official opening on July 21 1881 an estimated 40,000, almost the entire population of Adelaide, attended. During the 1889 flood, the weir was overwhelmed, its gates jammed, and in trying to free them the weir's designer John Langdon was crippled.^[28] The weir was rebuilt from 1928 to 1929 with its footbridge relocated and the centre section replaced. The gates can now be fully raised and the river allowed to flow unimpeded.^[29]

The "Popeye" boats are privately owned recreational ferries that operate on the lake between Elder Park and the Adelaide Zoo. The first Popeye boat was launched on the Torrens Lake by Gordon Watts in 1935. It was a 25 foot boat, built on the Banks of the Torrens to hold up to 20 passengers, and numbered Popeye 1. Watts purchased a former Glenelg cruise boat in 1948 and put it into service as Popeye 2. To 1950 three new jarrah hulled boats were built at Port Adelaide; carrying 40 passengers each they were numbered Popeye 3 through Popeye 5. Trips on the popeye from Elder Park to the zoo became a treasured family outing and the boats hosted weddings and other events.^[30] In March 1962 Keith Altman, owner of riverside eatery "Jolley's Boathouse", took over the Popeyes and introduced paddle boats to the river. They had a brush with royalty in March 1977 with Popeye 5 ferrying Queen Elizabeth II and Prince Philip, with a choir following in Popeye 4. The old boats were replaced in 1982 with 3 new fibreglass models, launched by the Prime Minister Malcolm Fraser, and now named Popeyes I, II and III.^[31]

[edit] Water use

In the early days of Adelaide, the Torrens was used for bathing, stock watering, rubbish disposal, water supply and as a de-facto sewer and drainage sump. This lead to a range of health issues until finally, in 1839, when a dysentery outbreak killed 5 children in one day, Governor Gawler forbid bathing, clothes washing and the disposal of animal carcases in the Torrens within 1 mile of town. The quality of the river's water was not helped by water supply methods. Carters used to drive water carts into the Torrens to refill. To prevent this the government built a facility with steam powered pumps and water storage in 1852, from which the carters then filled.^[32]

The "Waterworks act" of 1856 was passed to enable damming of the upstream Torrens for water supply purposes.^[33] The resulting water commission arranged the following year for foundations to be laid for a water supply weir. Poor construction materials and techniques lead to them being washed away, and the weir not completed. The government then created a waterworks department, which started construction of a weir and reservoir in 1859, at Thorndon Park partway through the river’s suburban flow. The weir was completed on June 4, 1860 and the reservoir began supplying piped water in December. The water was captured at the weir, piped for storage to the Thorndon park reservoir, piped to a water tank at Kent Town. Water from Kent Town storage was distributed via a manually controlled water system that was unmetered first six years.^[34] Within six years 20,000 citizens in Adelaide and Port Adelaide were connected to reticulated Torrens water.^[35] By 1872, the 2840 megalitre Hope Valley Reservoir in the Adelaide hills foothills was completed as a storage reservoir, supplied via an aqueduct and tunnel.^[36]

Public baths were built in 1861 just north of the current Parliament building. They were supplied with reticulated water from the Torrens and progressively upgraded with the last a 1940 remodelling including an Olympic size swimming pool and diving tower. The baths were demolished in 1970 to make way for the Adelaide Festival Centre.^[37] The 16,500 megalitre Millbrook reservoir was constructed high in the Adelaide Hills from 1913 to 1918 submerging the town of Millbrook. An earth bank dam fed by mile long tunnel from a weir on the river at Gumeracha, its elevation allows gravity supply of water to Adelaide's Eastern suburbs.^[38]

[edit] Bridges

Due to the river's path through the centre of Adelaide, transport necessitated the construction of many bridges. Prior to the bridges all crossings had been via fords which proved a dangerous practice in spring and winter. The first bridge was one of timber built in 1839 approximately 500 metres west of the current City bridge, but destroyed by floods in September 1844.^[39] In 1849 £6000 was allocated to bridge the Torrens, but by 1852 three wooden bridges had been built and all destroyed in floods.^[33] In June 1856 the English manufactured, iron City Bridge was opened, extending King William street to North Adelaide. It was widened in 1877 then converted into a two lane bridge in 1884. The bridge was replaced in 1931 with the current concrete arch structure.^[40]

The Victoria Bridge extends from Morphett street and crosses the rail lines from the Adelaide Railway Station and the river. The first bridge was opened on June 21, 1871,^[33] and over time various bridges have been built on the same site. The current bridge, a prestressed concrete box girder bridge, was opened in March 1968 by Don Dunstan and Lord Mayor Walter Lewis Bridgland. The bridge is actually two bridges joined to appear continuous. The first spans North terrace and the rail lines with the second the river. The bridge was designed without a central pillar in the river, allowing three lanes of rowers to compete without interference.^[41]

The Albert Bridge is adjacent to the Adelaide Zoo and carries Frome Road over the river. A timber bridge was constructed in 1859, west of the current bridge, and named the Old Frome Bridge.^[42] The current bridge was named after Prince Albert, Later King Edwards VII, and opened in his presence on May 7, 1879.^[43] The bridge is made from three English built parallel wrought iron, scollaped girders. It is 120 feet long with a cantilevered span of 60 feet. The bridge is 43 feet wide and originally had a timber deck which was replaced with concrete in 1922. The bridge is listed on the "City of Adelaide Heritage Register", the "South Australian Heritage Register" and the "Register of the National Estate". A complete restoration was finished in 1982, with the bridge now appearing as it did at the 1879 opening.^[44]

The Hackney Bridge was first known as the "Second Company Bridge" as it was built by the South Australia Company. The bridge was built so that wheat farmers from the northern side could access the South Australian Company's flour mill which stood where the Hackney Hotel was later built.^[42] The current bridge is the third at the same site: in 1845 "prescotts crossing" was built as a timber beam bridge, 1860 saw it replaced with a four span, trussed timber bridge. The current bridge is a 126 foot long, 34 foot wide truss arch bridge opened on December 5, 1885.^[45]

University Footbridge connects Victoria Drive, at the rear of University of Adelaide, with Peace Park adjacent to Memorial drive.^[46] The bridge was conceived in 1928 by an engineering undergraduate at the university and funded with a 26,000 pound grant from Adelaide City Council. It was designed by university staff under the supervision of Robert Chapman, Chief engineer of the South Australian Railways. Construction was delayed until 1937 due to the economic effects of the great depression. The bridge has an arch spanning 152 ft, 20 ft over the river, and was the first welded bridge in South Australia.^[47]

A notorious murder occurred in the vicinity of the bridge on 10 May 1972. University of Adelaide law lecturer Dr George Duncan was thrown into the river. A plaque exists on the bridge commemorating his death and the subsequent decriminalisation of homosexuality in South Australia.^[48]

Various other bridges have spanned the Torrens including:

• Railway Bridge, Built in 1856 to carry the Port and Gawler Town railway lines. The bridge was constructed 74 chains (1.5 km) from Adelaide Railway Station^[49]
• Felixstowe Bridge, built in 1873 on OG Road and reconstructed in 1892, 1901, 1924 and 1961. The first bridge was narrow, and hay-laden carts often damaged posts while brushing past them.^[42]
• Tennyson Bridge, built 1877 on Stephen Terrace, St Peters, replacing a ford at the same site.^[42]
• Ascot Bridge, built in 1970 to connect Ascot Avenue and Lower Portrush Road.
• Dickson's Crossing, built on Darley Road in 1977 to replace a ford.^[42]

[edit] Flora and fauna

The river was formerly a food source with yabbies, mussels and small fish, however the reduction in water quality, changing of the river’s habitat, and introduction of European fish species has led to a reduction in fauna quantity and diversity.^[17] Exotic pest species such as the European carp, trout and Redfin Perch have greatly reduced native fish populations like the big headed gudgeon but waterfowl are common along the river with black ducks, wood ducks, black swans, ibis, egrets and herons amongst the more than 100 species seen. The number of exotic waterfowl species such as mallards has reduced in recent years. In places the steep banks of the river are an ideal habitat for long-necked tortoises.

The river, and its tributaries, had a population of water rats (Hydromys chrysogaster) and swamp rats (Rattus lutreolus). Water rats remain in reduced numbers , but the introduced black rat (rattus rattus) and brown rat (Rattus norvegicus) have largely supplanted the natives. The house mouse is now the most common mammal of the Torrens environ.^[50]

Widely found native reeds, sedges and rushes along the upper river are bulrush, knobby club rush, spike rush, common reed, sea rush and pale rush. River red gum (Eucalyptus camaldulensis) and Blue gum (Eucalyptus leucoxylon) are found along the river banks, although far from the forest that was seen by European discoverers. Still present are many of the original vegetation species like: Sheoak (Casuarina Stricta), Native cherry (Exocarpos cupressiformis), Native pine (Callitris preissii) and Australia's floral emblem the Golden Wattle (Acacia pycnantha)^[51]

[edit] The river today

From its source the river flows westwards through Birdwood and Gumeracha . It then continues down through Torrens Gorge entering suburban Adelaide at the suburb of Athelstone with some of its path paralleled by the O-Bahn Busway. It passes between the city-centre and North Adelaide, forming the Torrens Lake between the Adelaide Zoo and a weir opposite Adelaide Gaol. The river then continues the remaining eight kilometres to the sea at Henley Beach South, emptying into Gulf St. Vincent via a constructed outlet.

The river's flow is captured by the Hope Valley, Millbrook and Kangaroo Creek reservoirs, which provide water storage for Adelaide. These reservoirs form part of the Adelaide Hills catchment, which supplies on average 60% of Adelaide's water needs. Adelaide City Council uses water from the lower river to irrigate the city's surrounding parklands.^[52]

The suburban end of the river is bounded by 35 km of linear parks, with numerous playgrounds walkways and bicycle tracks, which represent the earliest linear river park in Australia. On the south bank of the lake, adjacent to the Adelaide Festival Centre Elder Park is used for the annual Tasting Australia festival, mass singing of Christmas carols by candlelight as well as other public events throughout the year. The Popeye tourist boat, small paddle boats and black swans of the lake are icons of the area frequently featured in postcard photographs of the city. Due to now-limited natural river flow and stormwater born organic material the lower river, particularly the lake, is often polluted with algal blooms and significant levels of E. coli bacteria in spring and summer. Numerous taskforces have been formed to improve the river’s water quality, with the latest created by the Minister for the Environment and Conservation in 2006.^[53]

The river is a used by many for recreation, with the footpaths on the riverbanks often filled with cyclists and joggers. Rowers use the lake for training all year round, and many clubs such as the Adelaide University Boat Club and the Adelaide Rowing Club are located upon its banks. Several rowing regattas are held on the Torrens Lake Course in the summer months of each year, contested by both club and school crews.

[edit] Notes

[edit] References

[edit] External links

• Torrens Catchment Water Management Board
• State Library Manning Index: River Torrens