Geography of Sydney
The geography of Sydney is characterised by its coastal location on a basin bordered by the Pacific Ocean to the east, the Blue Mountains to the west, the Hawkesbury River to the north and the Woronora Plateau to the south. Sydney lies on a submergent coastline on the east coast of New South Wales, where the ocean level has risen to flood deep river valleys (rias) carved in the Sydney sandstone. Port Jackson, better known as Sydney Harbour, is one such ria.
The Sydney area lies on Triassic shales and sandstones. The region mostly consists of low rolling hills and wide valleys in a rain shadow area. Sydney sprawls over two major regions: the Cumberland Plain, a relatively flat region lying to the west of Sydney Harbour, and the Hornsby Plateau, a plateau north of the Harbour rising to 200 metres and dissected by steep valleys. Sydney's native plant species are predominantly eucalyptus trees, and its soils are usually red and yellow in texture. The endemic flora is home to a variety of bird, insect, reptile and mammal species, which are conspicuous in urban areas.
There are more than 70 harbour and ocean beaches in the urban area. Most of Sydney's water storages are on tributaries of the Nepean River. Parramatta River drains a large area of Sydney's western suburbs. With 5,005,400 inhabitants (as of 2016) and an urban population density of 2037 people per square kilometre, Sydney's urban area covers 1,788 km² (690 mi²), comprising 35% of Sydney and is constantly growing.
The rising sea level between 18,000 and 6,000 years ago flooded the rias to form estuaries and deep harbours. Erosion by coastal streams has created a landscape of deep canyons and remnant plateaus. The city has fault lines which run considerably deep beneath the Sydney basin, dating back to when New Zealand started breaking away from Australia more than 85 million years ago. To the east the basin continues to the edge of the continental shelf. The centre of the basin is located around 30 kilometres (19 mi) west of the Sydney central business district at Fairfield.
The sand that was to become the sandstone of today was washed from Broken Hill and laid down about 200 million years ago. The ripple marks from the ancient river that brought the grains of sand are distinctive and easily seen, telling geologists that the sand comes from rocks formed between 500 and 700 million years ago far to the south. This means that the highest part of the visible lines almost always faces approximately south. There are volcanic rocks from low hills in the shale landscapes. The Basin's sedimentary rocks have been subject to uplift with gentle folding and minor faulting during the formation of the Great Dividing Range.
At a time in the past, monocline formed to the west of Sydney. The monocline is a sloping bend that raises the sandstone well above where it is expected to be seen, and this is why the whole of the visible top of the Blue Mountains is made of sandstone. Sandstone slopes in the Sydney area are on three sides: to the west the Blue Mountains, and to the north and south, the Hornsby and Woronora plateaux'.
Being very porous, the Sydney sandstone has shale lenses and fossil riverbeds dotted throughout and it is some 200 metres (656 feet) thick. The sandstone was probably deposited in a freshwater delta and is the caprock which controls the erosion and scarp retreat of the Illawarra escarpment. Six kilometres of sandstone and shale lie under Sydney. Bringelly Shale and Minchinbury Sandstone are often seen in the greater western parts of Sydney. Ashfield Shale is observed in the inner western suburbs. These components are part of the Wianamatta Shale group. Mittagong Formation sighted in a few areas in northern Sydney.
Prospect Hill in western Sydney is the largest assemblage of igneous rock in Sydney. The oval-shaped ridge was made many millions of years ago when volcanic material from the Earth's upper mantle moved upwards and then sideways. Slow erosion of the overlying layers of sedimentary rock by the flow of rainwater have eventually laid bare the edges of the volcanic and metamorphic rocks of the intrusion. The Gap, an ocean cliff on the South Head peninsula in Watsons Bay, was laid as sediment more than 200 million years ago in the Triassic period. During the Jurassic era, a cataclysmic event resulted in an enormous crack forming within the strata. The Gap itself forms a sequence that continues offshore to the edge of the Sahul Shelf.
The Nepean River rises to the south in the Woronora Plateau, and wraps around the western edge of the city. Swamps and lagoons are existent on the floodplain of the Nepean River, one being Bents Basin, which is also a recreational area. Where the Nepean turns east it becomes the Hawkesbury River, which winds through the Hornsby Plateau before emptying into Broken Bay. Broken Bay and the lower Hawkesbury form the commonly accepted boundary between Sydney and the Central Coast to the north. The remaining section of Warragamba River flows 3.5 kilometres (2.2 mi) north-east from the Warragamba Dam spillway to its confluence with the Nepean River.
The south and southwest of Sydney is drained by the Georges River, flowing north from its source near Appin, towards Liverpool and then turning east towards Botany Bay. The other major tributary of Botany Bay is the Cooks River, running through the inner-south western suburbs of Canterbury and Tempe. The Georges River estuary separates the main part of Sydney's urban area from the Sutherland Shire. The Woronora River, on the southern edge of the Sydney Plain, flows in a steep-sided valley from the Woronora Dam to the eastern estuary of the Georges River. The Hacking River is further south and runs through The Royal National Park into Port Hacking which forms the southern boundary of the Sutherland Shire.
Parramatta River's headwaters are several local creeks including Toongabbie Creek and Hunts Creek, part of the upper Parramatta river catchment area. Hunt's creek flows from Lake Parramatta, a few kilometres North of Parramatta. At east Parramatta the river becomes a tidal estuary that flows into Port Jackson, commonly known as Sydney harbour. The reestablishment of foreshore mangroves has been a major focus of the ecological management of the Parramatta river and Sydney Harbour. Other major tributaries flow into Port Jackson from the North Shore and are the Lane Cove River and Middle Harbour Creek.
Minor waterways draining Sydney's western suburbs include South Creek and Eastern Creek, flowing into the Hawkesbury, and Prospect Creek draining into the Georges River. Cowan Creek and Berowra Creek run north from the Upper North Shore to the Hawkesbury river. Sydney has a number of islands in its harbour and surrounding rivers. Such islands include, Shark Island, Cockatoo Island, Clark Island, Snapper Island, Spectacle Island and Goat Island in Port Jackson. Bare Island in Botany Bay. Lion Island, Long Island and Milson Island in Hawkesbury River. Scotland Island in the Northern Beaches. And Rodd Island in Parramatta River.
Flora and fauna
The plant communities in the Sydney region are sclerophyll forests, which consist of wet and dry evergreen forests, thus making the city have two distinct biomes. Dry sclerophyll forests, reminiscent of Mediterranean forests, are the most predominant plants in the region, mainly occurring in the Cumberland Plain. They contain eucalyptus trees which are usually in open woodlands that have dry shrubs and sparse grass in the understory. On the other hand, wet sclerophyll forests, which are Temperate broadleaf and mixed forests, have narrow, relatively tall, dense trees with a lush, moist understorey of fleecy shrubs and tree ferns. Plant species within the wet sclerophyll zone include blue gum, karrabina, peppermints and eucalyptus oreades. Wet sclerophyll forests are found in the cooler or wetter areas such as Northern Suburbs, Forest District, North Shore and in the Blue Mountains.
Sclerophyll forests developed as a result of the extreme age of the continent combined with Aboriginal fire use. Deep weathering of the crust leached chemicals out of the rock, leaving Australian soils deficient in nutrients. The sandstone is the basis of the nutrient-poor soils found in Sydney that developed over millennia and 'came to nurture a brilliant and immensely diverse array of plants'. As plants cannot afford to lose leaves to herbivores when nutrients are scarce, they defend their foliage with toxins. In eucalypts, these toxins give the bush its distinctive smell. The first European settlers saw Sydney's vegetation as "extremely barren, poor, hungry sand, thickly studded with rocks, growing nothing but a few miserable stunted gums and dwarf underwood". It has been calculated that around 98,000 hectares of native vegetation remains in the Sydney metropolitan area, about half of what is likely to have been existing at the time of European arrival.
The Sydney Turpentine-Ironbark Forest, one of six main indigenous forest communities of Sydney, is an example of a dry sclerophyll forest, containing trees around 20–30 metres tall, with ground cover composed of flowering shrubs and native grasses. The Blue Gum High Forest, strictly found in northern parts of Sydney, is a wet sclerophyll forest example, where the annual rainfall is over 1100 mm (43 in). It has trees between 20 and 40 metres tall.
- Angophora costata (Sydney red gum)
- Eucalyptus piperita (Sydney peppermint)
- Eucalyptus sieberi (silvertop ash)
- Eucalyptus oblonga (stringybark)
- Eucalyptus capitellata (brown stringybark)
- Eucalyptus bosistoana (coast grey box)
- Eucalyptus moluccana (grey box)
- Corymbia gummifera (red bloodwood)
- Eucalyptus racemosa (snappy gum)
- Eucalyptus haemastoma (scribbly gum)
- Corymbia maculata (spotted gum)
- Eucalyptus luehmanniana (yellow top mallee ash)
- Eucalyptus eugenioides (thin-leaved stringybark)
- Eucalyptus robusta (swamp mahogany)
Non-eucalyptus tree species:
- Araucaria cunninghamii (hoop pine)
- Araucaria bidwillii (bunya pine)
- Corymbia eximia (yellow bloodwood)
- Allocasuarina torulosa (forest oak)
- Melaleuca linariifolia (snow-in-summer)
- Melaleuca quinquenervia (broad-leaved paperbark)
- Melaleuca alternifolia (narrow-leaved paperbark)
- Melaleuca armillaris (bracelet honey myrtle)
- Melaleuca decora (white feather honeymyrtle)
- Tristaniopsis laurina (water gum)
- Acacia falcata (sickle wattle)
- Callitris endlicheri (black cypress pine)
- Grevillea robusta (Australian silver oak)
- Acacia longifolia (Sydney golden wattle)
- Acacia podalyriifolia (Mount Morgan wattle)
- Melaleuca quinquenervia (paperbark tea tree)
- Syncarpia glomulifera (turpentine tree)
- Syzygium smithii (black cypress pine)
- Banksia integrifolia (coast banksia)
- Brachychiton acerifolius (Illawarra flame tree)
- Brachychiton populneus (Kurrajong)
- Melaleuca viminalis (weeping bottlebrush)
- Cupaniopsis anacardioides (tuckeroo)
- Ficus macrophylla (Moreton Bay fig)
- Ficus microcarpa (Hill's weeping fig)
- Ficus rubiginosa (Port Jackson's fig)
- Flindersia australis (crow's ash)
- Glochidion ferdinandi (cheese tree)
- Lophostemon confertus (brush box)
Common shrub species include, but are not limited to:
- Banksia serrata (old man banksia)
- Casuarina glauca (swamp oak)
- Ceratopetalum gummiferum (New South Wales Christmas bush)
- Lomandra longifolia (spiny-head mat-rush)
- Banksia spinulosa
- Xanthosia pilosa (wooly xanthosia)
- Banksia aemula (wallum banksia)
- Banksia robur (swamp banksia)
- Melaleuca citrina (lemon bottlebrush)
- Melaleuca linearis (narrow-leaved bottlebrush)
- Jacaranda mimosifolia (blue jacaranda)
- Cinnamomum camphora (camphor laurel)
- Pinus Radiata (Monterey pine)
- Plumeria rubra (red frangipani)
- Liquidambar styraciflua (sweet gum)
- Platanus × acerifolia (London planetree)
- Vachellia farnesiana (Mimosa bush)
- Ailanthus altissima (tree of heaven)
- Olea africana (African olive)
- Gleditsia triacanthos (honey locust)
- Eriobotrya japonica (Japanese medlar)
- Araucaria heterophylla (Norfolk Island pine)
- Thunbergia grandiflora (blue skyflower)
- Alternanthera philoxeroides (alligator weed)
- Anredera cordifolia (Madeira-vine)
- Asparagus aethiopicus (Asparagus fern)
- Lantana camara (West Indian lantana)
- Cestrum nocturnum (night-blooming jasmine)
- Senna septemtrionalis (arsenic bush)
- Ochna serrulata (Mickey mouse plant)
- Ligustrum sinense (small-leaved privet)
- Solanum mauritianum (wild tobacco bush)
- Talinum paniculatum (jewels-of-opar)
- Subtropical rainforests - Found in areas around Royal National Park, Helensburgh and Illawarra escarpment to the south of Sydney, albeit in very small, isolated portions.
- North Coast Warm Temperate Rainforests - Dominated by Ceratopetalum apetalum, Doryphora sassafras and Acmena smithii, it is scarcely present in the RNP and Hacking River valley in around Sutherland in southern Sydney, and predominant in the Ku-ring-gai Chase National Park and Turramurra in Northern Sydney, near Hornsby.
- Dry Rainforests or Western Sydney Dry Rainforest - A component of the Cumberland Plain Woodland, it is distributed across the dry areas to the south of Blue Mountains and in small portions in Calmsley Hill Farm in Western Sydney Parklands, near Abbotsbury, New South Wales. They have Alectryon subcinereus and Clerodendrum tomentosum as shrubby covers.
- Littoral Rainforests - Dominated by Acmena smithii, Ficus rubiginosa, and Elaeodendron australe, it occurs in sporadic areas in northern Illawarra to Royal National Park (near Bundeena and in Towra Point Nature Reserve in Sutherland Shire), and also in one diminutive area in Pittwater Council (Mona Vale) in the Northern Suburbs to Newcastle.
- Wet scleropyhll forests
- North Coast Wet Sclerophyll Forests - Dominated by tall Eucalyptus saligna and Eucalyptus pilularis Blue Gum trees and receiving high amount of rainfall (above 1000 mm), it is present in Ku-ring-gai Council, Hornsby Shire, Narrabeen, Lane Cove, Pennant Hills and Castle Hill in the north, and in the Illawara region, with small portions in Ryde, North Parramatta and Pittwater.
- Northern Hinterland Wet Sclerophyll Forests - Dominated by Eucalyptus resinifera and Syncarpia glomulifera, it was once extensive on the north shore across the local government areas of Hornsby, Ku-ring-gai, Ryde, Willoughby, Lane Cove, Parramatta, Baulkham Hills and Blacktown to the north of Sydney, with small outliers in Menai, Bankstown and Auburn in the southwest.
- Southern Lowland Wet Sclerophyll Forests - Containing Corymbia maculata, it is found in upper Narrabeen, Pittwater, Woronora and Illawara, as well as on the foreshores of Hacking, Parramatta and Georges Rivers.
- Dry sclerophyll forests
- Cumberland Plain Woodland - These are shrub and grass eucalyptus communities located in areas of low to moderate rainfall (less than 950 millimetres annually) and are most commonly found in large parts of the Sydney metropolitan area, namely in Western Sydney or the Cumberland Plain. Moist Shale Woodlands also exist within this biome, but they're distinguished by their lusher plant habitats.
- Sydney Coastal Dry Sclerophyll Forests - Predominant on the northeast parts of the Woronora Plateau on ridgelines within the Royal, Heathcote and Dharawal national parks and Garawarra State Conservation Area in southern Sydney. It is also present in north of Sydney Harbour and extends to both sides of the Hawkesbury River.
- Sydney Hinterland Dry Sclerophyll Forests - Found in the drier parts (less than 950 mm) of the Woronora Plateau, also in Appin, Sandy Point, pockets in the southwestern edges of the Cumberlan Plain (on the doorsteps of the Blue Mountains), and on the foreshores of the Hawkesbury River, it features 10-25 m tall eucalyptus trees with ostensible sclerophyll shrub understorey and open groundcover of sclerophyll sedges.
- Sydney Sand Flats Dry Sclerophyll Forests - Present in northern Holsworthy with smaller examples at Rookwood and Villawood and is dominated by Eucalyptus sclerophylla.
- Coastal Dune Dry Sclerophyll Forests - Examples are found at Bundeena, Kurnell and La Perouse in southern Sydney containing a collection of sclerophyllous shrub and heath species and a ferny ground cover.
- Wallum Sand Heaths - Present in Pleistocene sand dunes sitting high on sandstone cliff tops between Bundeena in Royal NP, Woollahra, Kurnell peninsula, Narrabeen and Sydney Heads which contain Allocasuarina distyla, Banksia serrata and Banksia aemula. There are also a wide variety of woody species such as tea-trees, grevilleas, peas and wattles. The ground layer comprises on open cover of sedges and forbs.
- Sydney Coastal Heaths - Found extensively in the Sydney metropolitan area and in the eastern parts of the Woronora and Hornsby plateaus particularly in Royal and Ku-ring-gai national parks with prominence of Eucalyptus luehmanniana.
- Coastal Headland Heaths - Found in and around Garie Beach on the outskirts of southern Sydney, near Royal NP.
- Freshwater Wetlands
- Coastal Heath Swamps - Common in Holsworthy defense area, Woronora catchment area and the Hornsby plateau including Garigal and Ku-ring-gai Chase national parks.
- Coastal Freshwater Lagoons - Occurs on poorly drained alluvial flats and sand depressions and may be surrounded by broad-leaved cumbungi (Typha orientalis).
- Forested wetlands
- Coastal Swamp Forests - Occupies the low-lying coastal river flats, swamps and sand depressions, which are mostly cleared from the Sydney metropolitan area, but still exist in places like Georges River National Park, Milperra, Chipping Norton, Prospect Creek and Kurnell in southeastern Sydney, and Wheeler Heights, Narrabeen and Dee Why in the Northern Beaches.
- Coastal Floodplain Wetlands - They cover a series of eucalypt and casuarina dominated communities found on low-lying coastal alluvial soils, such as in Georges River and its tributaries in northern Woronora and the lowlands of Blue Mountains. They are dominated by Microlaena stipoides.
- Eastern Riverine Forests - Many riparian scrubs are found on rocky creeks that are enclosed with coarse sandy alluvial deposits with common vegetation being Tristaniopsis laurina.
- Saline Wetlands
- Mangrove Swamps - Common in Towra, they're a basic community dominated by either Avicennia marina or Aegiceras corniculatum.
- Saltmarshes - Usually located on estuarine alluvial soils, small tracts also exist on headlands exposed to prevailing sea spray.
- Seagrass Meadows - Occurring on sandy nether of coastal estuaries and bays, they include a number of subaqueous aquatic species, such as eel grass (Zostera spp) and sea grass (Posidonia australis).
The fauna of the Sydney area is diverse and its urban area is home to variety of bird and insect species, and also a few bat, arachnid and amphibian species. Introduced birds such as the house sparrow, common myna and feral pigeon are ubiquitous in the CBD areas of Sydney. Moreover, possums, bandicoots, rabbits, feral cats, lizards, snakes and frogs may also be present in the urban environment, albeit seldom in city centers.
About 40 species of reptiles are found in the Sydney region and 30 bird species exist in the urban areas. Sydney's outer suburbs, namely those adjacent to large parks, have a great diversity of wildlife. Since European settlement and the subsequent bushland clearing for the increasing population, 60% of the original mammals are now considered endangered or vulnerable, and many reptile species are experiencing population diminution and are becoming elusive.
This list includes bird species that are widespread in the Sydney metropolitan area:
- Australian magpie
- Australian raven
- Australian white ibis
- Bell miner
- Common starling
- Crested pigeon
- Eastern rosella
- Eastern spinebill
- Grey butcherbird
- Laughing kookaburra
- Magpie lark
- Masked lapwing
- Noisy miner
- Pacific koel
- Pied currawong
- Rainbow lorikeet
- Spotted dove
- Silver gull
- Sulphur-crested cockatoo
- Superb fairy-wren
- Willie wagtail
This list includes mammal, reptile and amphibian species that are spotted in the Sydney urban area:
- Australian blue-tongued skink
- Australian green tree frog
- Bush rat
- Common bent-wing bat
- Common brushtail possum
- Common ringtail possum
- Common garden skink
- Diamond python
- Eastern brown snake
- Golden bell frog
- Golden water skink
- Grey-headed flying fox
- Peron's tree frog
- Red-bellied black snake
- Snake-eyed skink
- Three-toed earless skink
This list includes insect, spider and centipede species that are commonly present in Sydney:
- Australian painted lady
- Bess beetle
- Black house spider
- Christmas beetle
- Funnel ant
- Green vegetable bug
- House centipede
- Orchard swallowtail butterfly
- Redback spider
- Skull spider
- Spider wasp
- Sydney funnel-web spider
- Sydney huntsman spider
- Transverse ladybird
The oldest parts of the city are located in the flat areas south of the harbour; the North Shore was slower to develop because of its hilly topography, and was mostly a quiet backwater until the Sydney Harbour Bridge was opened in 1932, linking it to the rest of the city, with the suburbs surrounding the northern entrance to said bridge effectively developing North Sydney into a second central business district.
The extensive area covered by urban Sydney is formally divided into more than 300 suburbs for addressing and postal purposes, and administered as 38 local government areas. The City of Sydney itself covers a fairly small area comprising the central business district and its neighbouring inner-city suburbs. Sydney's central business district (CBD) extends southwards for about 2 kilometres (1.25 mi) from Sydney Cove, the point of the first European settlement. The west side is bounded by Darling Harbour, a popular tourist and nightlife precinct while Central station marks the southern end of the CBD. George Street serves as the Sydney CBD's main north-south thoroughfare.
The Eastern Suburbs sit on the coast of Sydney. They contain iconic beaches such as Bondi Beach and Coogee beach, and feature prominent seaside cliffs. The suburbs of Maroubra, Coogee and Bondi Junction lie on steep slopes, and would have an elevation of 90 metres (295 feet) at the highest peaks. The Northern Suburbs of Sydney are characterised by pristine waterways with immense greenery and large plots of manicured land. Being around 80 to 180 metres (260 to 590 ft) above sea level, the region is very hilly and has a higher elevation than the rest of Sydney. Most of the North Shore suburbs are part of the Hawkesbury Plateau, a large sandstone plateau overlaid by a system of hilly ridges and gullies. Major waterways in the region include the Parramatta River, Lane Cove River and the many creek systems that branch out from these. The region is home to many parks and nature reserves — The Lane Cove National Park and the Garigal National Park include many areas of remnant bushland adjacent to the Lane Cove River and Middle Harbour. The Hills District, situated halfway between the northern suburbs and greater western Sydney, is a region so named for its characteristically comparatively hilly topography, akin to the Northern Suburbs and North Shore. Several of its suburbs have the word 'Hills' in their names. As the name indicates, the Hills District, depending on the suburb, is around 80 to 180 metres (260 to 590 ft) above sea level. As such, its elevation creates orographic rainfall brought in by onshore winds from the Pacific Ocean.
The western suburbs predominantly lie on the Cumberland Plain and are relatively flat in contrast to the above regions. They are situated on a rain shadow, thanks to the Hills District to the northeast. Thus, they tend to be drier than the coast and less lush than the hilly Northern Suburbs. Despite being known as "flat", there are a number of ridgy areas on the plain — Western Sydney Parklands and Prospect Hill are between 130 to 140 metres (430 to 460 ft) high. Highly elevated suburbs, which typically range between 70 to 100 metres (230 to 330 ft) in height, include Leppington and Oran Park to the southwest, Pemulwuy, Cecil Hills and Horsley Park to the greater west, and Greystanes, Seven Hills and Mount Druitt to the northwest. Agriculture is mainly concentrated in the outskirts of the Greater Western Sydney area, such as in suburbs of Kemps Creek, Orchard Hills, Luddenham and Horsley Park, among others, which lie in a countryside.
The Sydney CBD contains prominent parks such as, Hyde Park, The Domain and Royal Botanic Gardens and Farm Cove on the harbour. Other parks in that vicinity include Wynyard and Hyde Park. The Royal Botanic Gardens is the most important green space in the Sydney region, hosting both scientific and leisure activities. There are 15 separate parks under the administration of the City of Sydney. The Royal National Park was proclaimed on 26 April 1879 and with 13,200 hectares (51 square miles) is the second oldest national park in the world.
The largest park in the Sydney metropolitan region is Ku-ring-gai Chase National Park, established in 1894 with an area of 15,400 hectares (59 square miles). It is regarded for its well-preserved records of indigenous habitation and more than 800 rock engravings, cave drawings, and middens have been located in the park. The Domain is the oldest public parkland in Australia and measures 16.2 hectares (0.1 square miles) in area. Its location was used for both relaxation and the grazing of animals from the earliest days of the colony.
The inner west suburbs include Centennial Park and Moore Park in the east, Sydney Park and Royal National Park in the south, Ku-ring-gai Chase National Park in the north, and Western Sydney Parklands in the west. Other major parks in the Sydney metropolitan area include Auburn Botanical Gardens, Central Gardens Nature Reserve, Heathcote National Park, Georges River National Park, Lane Cove National Park and Blue Mountains National Park. There are large parks and reserves surrounding prominent bodies of water, such as those around Prospect Reservoir, Chipping Norton Lake, Lake Parramatta and Nepean River (Bents Basin).
Sydney has some of the finest and most famous beaches in the world. There are well over 100 beaches in the city, ranging in size from a few feet to several kilometres, located along the city's Pacific Ocean coastline and its harbours, bays and rivers. With around 70 surf beaches and dozens of harbour coves, Sydney is almost unrivalled in the world for the number and quality of beaches available. The water and sand among the city beaches, despite their popularity, are remarkably clean. The beach watch program was established in 1989 in response to community concern about the impact of sewage pollution on human health and the environment at Sydney's ocean beaches.
There are a number of informal regional names describing large sections of the urban area. Not all suburbs are necessarily covered by any of the following informal regional categories.
The regions are Canterbury-Bankstown, the Eastern Suburbs, the Forest District, Greater Western Sydney, the Hills District, the Inner West, the Macarthur region, the Northern Beaches, the Northern Suburbs, the North Shore, Southern Sydney, South-western Sydney, the St George district, the Sutherland Shire and Western Sydney. The Blue Mountains are at times considered to be part of Sydney's metropolitan area.
The largest commercial centres outside of the CBD are North Sydney and Chatswood in the north, Parramatta to the west, Liverpool in the south-west, Hurstville in the south, and Bondi Junction to the east. There has been accelerating commercial development in Parramatta since the 1950s as firms serving Western Sydney have set up regional offices and recognised the region's significant residential population mass and cheaper rents.
Sydney has a humid subtropical climate (Cfa) with warm, sometimes hot summers, and winters shifting from mild to cool. Although Sydney is predominantly humid subtropical, the hilly wet areas in the North Shore, Northern Suburbs, Forest District and Hills District have an oceanic climate (Cfb). The weather is moderated by proximity to the ocean, and more extreme temperatures are recorded in the inland western suburbs.
The warmest month in the CBD is January, with an average air temperature range at Observatory Hill of 19.6–26.5 °C (67.3–79.7 °F). The coldest month is July, with an average range of 8.7–17.4 °C (47.7–63.3 °F). In the west, the temperatures average between 17.5–28.4 °C (63.5–83.1 °F) in summer. In winter, they're normally between 6.2–17.4 °C (43.2–63.3 °F). In late spring and summer, Sydney can sometimes get northwesterly winds from the Outback, which are dry and hot, making the temperatures reach above 40 °C (104.0 °F). Frost is oftentimes observed in the outer suburbs.
Rainfall is spread throughout the year, but is slightly higher during the first half of the year when easterly winds dominate. Sydney's coast generally receives around 1,000 mm (39.37 in) to 1,200 mm (47.24 in) of rain annually. The western suburbs receive around 800 mm (31.50 in) to 900 mm (35.43 in) of precipitation, since moist onshore winds don't penetrate inland. Australian east coast low brings large amounts of rain in late autumn and winter.
- Sydney basin
- Geology of New South Wales
- Geology of Australia
- Cumberland Plain
- Sydney sandstone
- Bald Hill Claystone
- Geography of Australia
- Geography of New South Wales
- List of beaches in Sydney
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