|Name origin: In honour of Henry Hacking, a pilot at Port Jackson|
|State||New South Wales|
|Regions||Sydney basin (IBRA), Southern Sydney|
|Local government areas||Wollongong, Sutherland|
|- location||below Kellys Falls|
|- elevation||91 m (299 ft)|
|- location||west of|
|- elevation||7 m (23 ft)|
|Length||26 km (16 mi)|
|National park||Royal National Park|
|Nature reserve||Garawarra State Conservation Park|
The Hacking River is a watercourse that is located in the Southern Sydney region of New South Wales in Australia. The river is named in honour of Henry Hacking, a pilot at Port Jackson in colonial New South Wales.
Drawing its source from the east north-eastern runoff of the Illawarra escarpment, drained via Kellys Creek, the Hacking River rises below Kelly Falls, about 3 kilometres (1.9 mi) south of , east of the Princes Highway and west of . The river flows generally north north-east before reaching its mouth and emptying into Port Hacking at a line between Grays Point and Point Danger, about 4 kilometres (2.5 mi) east of the suburb of , west of . The river descends 84 metres (276 ft) over its 26-kilometre (16 mi) course. Although the Illawarra escarpment has a substantial rainfall, in dry periods, the river can be reduced to a mere trickle, resulting in connected puddles rather than a constant healthy flow.
Most of the river flows through the Garawarra State Conservation Park and the Royal National Park. However, at its upper reaches it has been subject to the impacts of urbanisation (Helensburgh and Otford), rural activities, and a large coal mine. The construction of the Princes Highway and the Sydney to Wollongong railway each have had impacts on the river. Many parts of what is now Royal National Park had been subjected to one form or another of exploitation, with consequential impacts on the river.
Its upper reaches lie adjacent to the red and green spots of the bright Garawarra State Conservation Area, where it is a small stream in a gully within rainforest. The river passes through a variety of plant communities, such as dry eucalyptus forest, tall wet eucalyptus forest and rainforests. Significant rainforest plants growing by the river banks include White Beech, Citronella, Supplejack, Bangalow Palm, Jackwood and Golden Sassafras. The Blackbutt, Grey Ironbark and Sydney Blue Gum are common eucalyptus trees. As it moves downstream, it flattens and widens before it reaches the estuary at Port Hacking.
A variety of molluscs, crustaceans, insects, fish and birds live in and around the river. Long Finned Eels migrate from oceanic spawning grounds as elvers. As adults they mature in the creeks and streams of the Royal National Park, sometimes to be seen in the river pools. Jollytail are common small fish. Platypus may occasionally be seen in the river, and Azure Kingfishers nest in the river banks. The land snail Meridolum marshalli is restricted to Royal National Park; its main habitat is wet areas near the river.
History and human development
For more than 8,000 years prior to 1840, the Tharawal (or Dharwal) people occupied the catchment area evidenced by hundreds of Aboriginal artefacts, middens, rock carvings and cave paintings. In the mid 19th century shell grit was in high demand as a source of lime for building in the Sydney district. Consequently, mud and oyster rocks were collected in large numbers from Port Hacking catchment destroying a number of aboriginal midden sites in the region.
The river is crossed by two causeways at the village of Otford near its headwaters, the Upper Crossing (below Waterfall and above the confluence with Waterfall Creek) and at Audley. The causeway, built in 1899, at Audley within the Royal National Park. Here, mangrove flats were cleared to make way for boat-sheds and accommodation in the late 19th century. A boatshed and picnic grounds remain at Audley, having been used continuously since. Visitors can canoe and kayak further upstream along the Hacking River or its tributary Kangaroo Creek.
The soft soils are vulnerable to erosion, which is exacerbated by bushwalking. Erosion is facilitated by relatively high rainfall in the Garrawarra State Conservation Area. Furthermore, runoff from the towns of Helensburgh, Otford and Stanwell Tops (which lie above the catchment) has also impacted on water quality in the river, resulting in increased turbidity and algal growth.
Within the Royal National Park at, visitors have enjoyed picnic and boating facilities for more than a hundred years.
A consequence of the weir was to divide the river into freshwater/saltwater tidal components. Impacts were to impede fish migration and to cause the accretion of sediment behind the weir. In flood, the road across the causeway is impassable, thus isolating the villages of Bundeena nad Maianbar. As the Upper Causeway would also flood in these conditions, an all-weather bridge was built at the Uppwr Causeway.
The tide reaches the weir, and although there is some lag, there is virtually no tidal prism. From the weir, the river continues downstream in the main through the Royal National Park, although towards its fluvial delta at Grays Point, it flows on one side through the suburbs of Kirrawee and Grays Point. It is opposite Grays Point that Muddy Creek joins the River. From this point downstream the river is characterised by large stands of mangroves and an extensive fluvial delta. Historically, the fluvial sediments below the weir have been restrictive to navigation. After the declaration of the National Park, the Trustees were concerned to facilitate boat access to the new park and consequently training walls were built. Subsequently, as navigation increased, there was repeated pressure for dredging. The fluvial delta has not been dredged foe many years. Nonetheless, there is a well-used boating facility at Swallow Rock (Grays Point).
- "Hacking River". Geographical Names Register (GNR) of NSW. Geographical Names Board of New South Wales. Retrieved 29 December 2013.
- "Port Hacking (Bay)". Geographical Names Register (GNR) of NSW. Geographical Names Board of New South Wales. Retrieved 8 January 2013.
- "Map of Hacking River, NSW". Bonzle Digital Atlas of Australia. Retrieved 29 December 2013.
- "Hacking River". NSW Water Quality and River Flow Objectives. Government of New South Wales. 1 May 2006. Retrieved 20 August 2011.
- NSW National Parks & Wildlife Service (February 2000). "Royal National Park, Heathcote National Park and Garawarra State Recreation Area: Plan of Management" (PDF). Sydney: Government of New South Wales. Retrieved 20 August 2011.
- Floyd, A. G. (1990). Australian Rainforests in New South Wales. Volume 2. p. 116. ISBN 0-949324-32-9.
- "Otford Eco".
- "Port Hacking Integrated Environmental Management Plan" (PDF). Sutherland Shire Council. 2008. p. 31. Retrieved 8 January 2012.
- Curby, Pauline (2002). [http://books.google.com.au/books? An important consequence of the causeway (weir) was to separate the river into freshwater and salt water/tidal components.. Impacts arising from this was to impede fish migration and to cause sediment accretion on the upstream side of the weir. ..rid=SBHBi1umJccC&pg=PA35&dq=%22Hacking+River%22&hl=en&ei=xcBPTrKUD6aKmQWZtenmBg&sa=X&oi=book_result&ct=result&resnum=8&ved=0CFEQ6AEwBw#v=onepage&q=%22Hacking%20River%22&f=false Pictorial History Sutherland Shire]. Kingsclear Books Pty Ltd. p. 36. ISBN 0-908272-79-0.
- Albani, A. D.; Cotis, George (2013). Port Hacking: Past and present of an estuarine environment.