North Stradbroke Island facts
Find out more about Landform History, Hydrogeology, Key Fauna & Flora Facts, Key Water Resources Facts.
At CRL, we are very proud to be associated with one of Australia’s most beautiful islands. We take very seriously our responsibility to deliver best practice environmental management programs and ensure a prosperous and sustainable future for generations to come.
North Stradbroke Island (NSI) is 32 kilometres long, 11 kilometres at its widest cross-section and 285 square kilometres in area (equal to 27 500 hectares).
Indigenous occupancy of these lands and waters date back some 20,000 years. These communities have long held strong and passionate feelings about any form of disturbance of the land, which they call Mother.
Their travel extended from the Brisbane River and Moreton Island in the North, through to Logan River and South Stradbroke Island in the South, as they hunted, gathered and met with other tribes of the area for cultural exchange. Each year they visited the Bunya Mountains for several weeks for corroborree (song and dance), feasting, trade, and competition, along with tribes from southern Queensland.
In the mid 1800's European settlement occurred. A mission was established at Moongalba and the days of roaming and hunting ceased. Movements to and from the island were controlled by a process of applying for access permits. Traditional customs and practices were prohibited, but did not entirely disappear.
The indigenous community belongs to the Jandai language group and comprises three groups, Noonuccal (Amity Point area), Koenpul (South of Dunwich) and Ngugi (Moreton Island).
The island is now a major tourist destination and is the most accessible island within a chain of barrier islands in Moreton Bay, adjacent to Brisbane.
Point Lookout, Amity and Dunwich are the three main settlements on 'Straddie' as it is colloquially known. It has a total permanent population of more than 3,500 with numbers swelling during peak holiday periods.
The major tourist centre is located at Point Lookout, named by Captain James Cook on his discovery voyage to the east coast of Australia in 1770.
Here visitors can enjoy world class beaches, famous for fishing and surfing, watch humpback whales on their Northern migration, scuba dive nearby rocky reefs or simply soak up the laid back island lifestyle.
Amity Point is located on the island’s north-western corner, directly opposite Moreton Island. This is a quiet fishing community and a popular boat launching point into Moreton Bay.
The township of Dunwich is the central visitor access point for North Stradbroke Island. Dunwich’s history dates back to 1827 when the area was established as a convict settlement. Dunwich was also the site of a quarantine station and a benevolent society for the care of elderly people. The historic graves at Dunwich cemetery bear testament to the harshness of life during this time.
The island’s most significant industry, sand mining, emerged in the late 1940’s. Since then approximately 15 percent of the island has been mined and revegetated by four different companies.
The island is a haven for commercial fish netting and trawling boats, which harvest mostly mullet from Moreton Bay and surrounding beaches during the winter months. North Stradbroke Island’s oysters, grown predominantly on the bay side of the island, are sought after Australia-wide for their quality and flavour.
Landform history
The island’s surface is a spectacular series of massive vegetated parabolic sand dune ridges visible from Brisbane and rising to 239 metres at Mt Hardgrave, five kilometres east of Dunwich. These dunes rest on a sea-cut basement platform, which is up to 40 metres below sea level and is composed of 400 million year old Palaeozoic age sedimentary and metamorphic rocks.
Weathering of the continental rocks of eastern Australia provided abundant sands, which were transported to the shoreline by rivers and then spread along the coast by northerly long-shore currents to form beaches, sand spits and dunes. The valuable rutile, zircon and ilmenite heavy mineral grains were separated by wave action from the lighter silica sands to give the rich 'black sand' strandline deposits on the beaches.
During more recent geological times, several intense natural variations in climate related to ice cap developments and periods of worldwide glaciations caused the sea level to fall up to 140 metres below present sea level, each time exposing large (formerly offshore) sand accumulations on the 40 kilometre-wide continental shelf, east of the island.
Periodic strong south-easterly winds and an arid climate killed the natural vegetation. From the abundant supplies of sand on the beaches and on the continental shelf, successive series of dunes were blown into place with inland concentrations of heavy minerals being formed during the process. The ‘ancient’ dune series formed 300,000 years ago, the ‘old’ dunes 150,000 years ago, and the two ‘recent’ series of dunes at 70,000 and 20,000 years ago.
About 6,500 years ago, during a short period of slightly elevated sea level, a coastal platform was eroded around the island's margin. Present-day beaches form the margins of this platform and support the fresh water swamps at the edges of the main island aquifer (underground water table). These swamps are home to a community of wetland plants and animals.
The geology we see today is only a snapshot in time, and we need to recognise that North Stradbroke Island is, and always has been, a dynamic and impermanent entity with a constantly changing geomorphology driven by the natural, and sometimes dramatic, variations in climate, which have been constant features throughout geological time.
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Hydrogeology
North Stradbroke Island’s main sand aquifer consists of clean quartz sand and is recharged by infiltration of rain through the unsaturated zone. Of the average 1600mm of annual rainfall, an estimated 400-800mm reaches the saturated zone. The balance is lost to interception, storage, evapotranspiration, or runoff into the ocean.
The NSI sand aquifer (groundwater table) contains an estimated 2.3 billion m3 of high quality water which is stored in pore spaces between the sand grains. The average salinity of the groundwater is 120mg/litre total dissolved salts (TDS) and it can be slightly acidic with free carbon dioxide often present.
Local perching layers have also formed on the island by organic material and partially cemented horizons. As a result, perched lakes have developed on North Stradbroke.
CRL’s two active mines – Yarraman and Enterprise – draw on the groundwater table for their mining operations. Freshwater is pumped from a number of groundwater bores and surface water features to maintain a moving dredging pond and to slurry sand for tailings pumping. The tailings placement from water slurry introduces water into the groundwater aquifer. Water losses from the bottom of the dredge pond also recharge the groundwater aquifer. Apart from some evaporation, all water is recycled back to the water table, ensuring CRL’s water usage is kept to a minimum. Routine monitoring of surface water levels, ground water levels and water quality allows CRL to develop responsible water management plans to minimise impacts on the water table.
Groundwater levels are measured at 203 sites (on and off lease) around the island using a network of groundwater piezometers and observation bores. A number of gauge boards and weirs in perched lakes, the keyhole lakes and at the pumping stations are used to monitor surface water levels. All water extracted for mining operations is measured using instantaneous flow gauges and cumulative flow metres to ensure that Department of Natural Resources, Mines and Water (DNRMW) licence allocations are not exceeded. This information along with aquifer parameters, rainfall, mine water usage and three-dimensional geometry is used to create numerical groundwater models for prediction of future groundwater conditions.
Water quality is measured at 33 surface water sites for selected physical and chemical parameters. Water quality monitoring is conducted to establish background conditions allowing CRL to develop water management plans to maintain the water quality and mitigate any impacts which may be identified.
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Key fauna & flora facts
- North Stradbroke Island is home to:
- Around 20 mammal species
- 20 species of frog
- 40 species of reptile
- More than 250 bird species
- 17 different plant formations are recognised on the island, comprising nearly 500 species
- Predominant species are Eucalyptus, Acacia, Banksia and Melaleuca
- The island is most commonly open forest with a heath understorey or tall shrubland with or without a heath understorey
- Vegetation in high dune areas is influenced by age of dune, aspect, rainfall patterns and exposure to prevailing winds
A number of significant flora and fauna species inhabit North Stradbroke Island. To learn more about these species and how CRL minimises the impact of mining operations on them, click here.
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Key water resource facts
- Average annual rainfall is 1,567mm at Point Lookout
- Average annual rainfall is 1,550mm at Dunwich
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