Hong Kong's geography: a drowned upland built at the water's edge

How a drowned dome made Victoria Harbour

The rocks under Hong Kong belong to the worn-down uplands of South China. Britannica describes the structure as an upfold running north-east to south-west, formed about 150 million years ago late in the Jurassic period. Lava filled it, and a granite dome later pushed up through the volcanic rock. Erosion stripped the centre of that dome, the sea flooded it, and the result is the harbour. The hills on either side are still partly capped with volcanic rock and fall to the water in steep concave slopes.

Victoria Harbour covered about 41.11 square kilometres in 2026, and it has been shrinking for as long as it has been charted. The name itself moved: the territory's Chinese name means fragrant harbour, and the British first called the water Hong Kong Harbour before renaming it after Queen Victoria. Zheng He's sailing maps of about 1425 show it, and the first detailed chart was made for the East India Company in 1810. Reclamation on both shores has joined former islands to the land: Stonecutters Island to New Kowloon, Kellett Island to Causeway Bay, Hoi Sham Island to To Kwa Wan, and Pillar Island and Mong Chau to Kwai Chung. Green Island, Little Green Island, Kowloon Rock and Tsing Yi remain islands. The last large reclamation proposed along the island shore from Sheung Wan to Causeway Bay drew organised opposition, and the Society for Protection of the Harbour was formed to resist further filling.

Pollution became the harbour's other question in the 1970s, as manufacturing grew. Club races in the harbour were stopped in 1973, and studies found decades of excess nitrogen arriving with the discharge of the Pearl River Delta.

Where Hong Kong's ridges run

The backbone of the territory is a set of ridges aligned with the structural grain of South China, and the alignment is visible in the line of Lantau Island and the Tolo Channel. From Tai Mo Shan, the highest summit, the ridges run south-west to Lantau, where Lantau Peak and Sunset Peak rise. South-east of Tai Mo Shan the line continues through Kowloon Peak and drops abruptly at Devil's Peak. On Hong Kong Island, Victoria Peak in the west and Mount Parker in the east shelter the harbour from the south.

Flat ground is scarce. Britannica puts floodplains, river valleys and reclaimed land together at less than a fifth of the land, and the only broad lowlands lie north of Tai Mo Shan in the Yuen Long and Sheung Shui plains. The urban area on the two sides of the harbour takes up only about a tenth of that level ground. Undeveloped land is mostly grassland, woodland, shrub and farmland on hill slopes.

The sea breaks the land into pieces. Besides Hong Kong Island and Lantau, the government counts 261 islands of 500 square metres or more. Hong Kong Island and its islets cover about 81 square kilometres in Britannica's figures, and urban Kowloon with Stonecutters Island about 47; the New Territories, which include the outlying islands, make up more than 90% of the total.

How much land Hong Kong actually has

The answer depends on what is counted and when. The government's own figure is land area alone, and it has risen with reclamation: 1,110.18 square kilometres in the brief published in 2021, 1,114.57 square kilometres on the fact page revised in July 2026. Wikipedia breaks the standard area down into land and inland water such as reservoirs and ponds, and gives a far larger figure, about 2,750 square kilometres, when the open sea under Hong Kong's jurisdiction is included. The territory's record on this site uses that larger figure, which is why it shows most of the area as water.

Reclamation is the only way the land figure grows. Wikipedia estimates reclaimed land at about 6% of the total land and about a quarter of developed space. Britannica notes that the area has continued to grow as more land has been reclaimed. The Victoria district on the north-west coast of the island, where the British first landed in 1841, sits on a shore pushed out by successive reclamations: the government's history records one finished in 1904 in Central, which produced Chater Road, Connaught Road and Des Voeux Road, and another in Wan Chai between 1921 and 1929.

The city's growth since the 1970s went north instead, into the New Territories, where the government decided in 1972 to build new towns. Nine were developed over the next two decades, and by 2021 they housed about 47% of the population.

Why Hong Kong has no river system

Britannica states it plainly: Hong Kong lacks a river system of any scope. The one exception is in the north, where the Sham Chun River, called the Shenzhen River on the mainland side, collects a few small tributaries, forms the boundary with Guangdong and runs into Deep Bay. Elsewhere the streams are short and cut across the north-east to south-west grain of the hills, and the reservoirs and catchwaters built on them have reduced the flow downstream.

That leaves rainfall and imports. Hong Kong has bought raw water from the Dongjiang, the East River in Guangdong, since 1965. In 2024 it imported about 820 million cubic metres, which the government's yearbook puts at 70 to 80% of the territory's fresh water consumption. The rest is caught locally: 2,310 millimetres of rain fell in 2024, and impounding reservoirs held about 410 million cubic metres at the end of that year.

Soils add to the shortage of good land. Britannica describes them as mostly acidic and of low fertility, red-yellow hill soils that thin quickly when the cover is stripped. The exception is the alluvium around Deep Bay, where silt from the Pearl River estuary settles out at high tide into mudflats and where paddy rice was once grown.

How the monsoon and typhoons divide the year

The Hong Kong Observatory describes a subtropical climate that tends towards temperate for nearly half the year. November and December are usually dry and sunny with comfortable temperatures. January and February are cloudier, with cold fronts and dry northerly winds; temperatures below 10 degrees Celsius are not uncommon in the urban areas, and frost forms at times on high ground and in the New Territories. March and April bring drizzle and fog that sometimes stops ferries and flights. From May to August afternoons often pass 31 degrees, nights stay around 26 and showers and thunderstorms are common.

Tropical cyclones may strike from May to November and are most likely from July to September. About 30 form in the western North Pacific and the China seas in an average year and about half reach typhoon strength, according to the Observatory, and Britannica puts the number affecting Hong Kong at an average of five or six a year. The Observatory notes that the landslips and floods following several days of cyclone rain sometimes do more damage than the wind.

Rain is unevenly spread. Mean annual rainfall ranges from about 1,400 millimetres at Ping Chau in the north-east to more than 3,000 near Tai Mo Shan, and about 80% of it falls between May and September. The government gives the territory-wide annual average as 2,431.2 millimetres. The records at the Observatory run from 0.0 degrees on 18 January 1893 to 36.9 degrees on 9 August 2026; the same day Sheung Shui reached 39.8 degrees, and Tai Mo Shan recorded minus 6.0 degrees on 24 January 2016.

Steep ground and heavy rain make the slopes a public works subject. The Lands Department inspects about 17,500 registered man-made slopes and maintained about 7,200 of them in 2024. That year the Civil Engineering and Development Department upgraded 150 government slopes, reduced the landslide risk of 37 natural hillside catchments and runs a landslip warning system for heavy rain.

What the country parks keep from building

The Country Parks Ordinance of 1976 provides the legal framework for the parks. In January 2025 the government counted 25 country parks and 22 special areas covering 44,842 hectares together, about 40% of the land, managed by the Agriculture, Fisheries and Conservation Department. Some 11 million visits were recorded in 2024. Eight marine parks and one marine reserve cover 8,517 hectares of sea, and 67 Sites of Special Scientific Interest are listed on land, Ma On Shan for its azaleas and Sha Lo Tung for its dragonflies among them.

The forest is mostly recent. Britannica records that centuries of cutting and burning left only about a sixth of the land forested, and that much of today's cover comes from planting since the Second World War, of pines, eucalyptus, banyan, casuarina and palms. The oldest woodland survives in the feng shui groves behind New Territories villages. The mammals are those that adapted to a crowded subtropical territory: two introduced monkeys, the rhesus macaque and the long-tailed macaque, live in the New Territories forests, and the largest carnivores left are rare small ones such as the South China red fox, the leopard cat and two civets. Tigers are said to have roamed the area once and are gone. Wikipedia counts more than 3,000 species of vascular plants in the territory, 300 of them native.

The north-west corner holds the wetland. The Mai Po Inner Deep Bay Ramsar Site covers about 1,500 hectares of mudflat, mangrove, fish ponds, tidal shrimp ponds and reed beds and has been listed under the Ramsar Convention since 1995. About 440 bird species have been recorded there, among them the black-faced spoonbill and the spoon-billed sandpiper.

The geology of the east is protected too. The Hong Kong UNESCO Global Geopark, inaugurated on 3 November 2009 and taken into UNESCO's Global Geoparks Network on 18 September 2011, covers more than 150 square kilometres of land in two regions. In Sai Kung the rock is the remnant of a supervolcano 140 million years old, set in hexagonal columns about 1.2 metres across on average and up to three metres, spread over about 100 square kilometres of land and sea. In the north-east New Territories a sedimentary sequence covers the period from 400 to 55 million years ago.

Where the city is meant to grow next

The government's plans look north again. Its forecast in the yearbook for 2024 expects about 3,000 hectares of spade-ready sites in the next decade if every procedure goes smoothly, around 1,700 hectares of them from the Northern Metropolis in the north of the territory. The first piece, the Hung Shui Kiu and Ha Tsuen New Development Area, is planned for about 66,700 flats and 184,000 more residents, and its first rehousing estate took in tenants in November 2024. The rest of the supply comes from brownfield sites, deserted farmland, the Tung Chung New Town Extension and near-shore reclamation at Lung Kwu Tan. How that land is used, and what it is used for, is the subject of Hong Kong: economy.