THE ENVIRONMENT
An important agricultural area is the alluvial plain around Yuen Long in the northwestern New Territories. These alluvial lowlands were probably formed within the last 33 000 years, and some areas are still prone to flooding. There are more than 5 000 hectares of floodplain in the territory and much of it is located in Yuen Long district. The natural deposition of sediment is continuing around the Deep Bay area, where brackish fish ponds have been established successfully in areas that once were mudflats, mangrove swamps or salt-water rice paddies.
As Hong Kong lacks large rivers, lakes or underground water supplies, reservoirs have been constructed in large valleys such as Shek Pik and Tai Lam Chung, and in coastal areas such as Plover Cove and High Island, where embayments and channels have been enclosed by large dams. In most instances, the catchment areas of the reservoirs have been designated as country parks.
A description of the onshore and offshore geology can be found in a series of new geological maps and memoirs produced and published at a scale of 1:20 000 by the Hong Kong Geological Survey, located within the Geotechnical Engineering Office. Detailed geological reports and maps at 1:5 000 scale have been published for Yuen Long, and are being prepared for Ma On Shan, North Lantau and Tsing Yi. Information about the terrain is also contained in the 55 maps and 12 reports of the Geotechnical Area Studies Programme. Published documents are available at the Government Publications Sales Centre.
Hydrography and Oceanography
Approximately two-thirds of the territory of Hong Kong, or almost 1830 square kilometres, is covered by the sea. Historically, the sea has been very important, as a highway for international shipping and in the form of a large and sheltered anchorage. Hong Kong is one of the busiest ports in the world. Offshore areas have assumed greater importance in recent years with the increasing number of engineering projects offshore, including reclamations, the construction of tunnels and pipelines and cable-laying. They are also an important source of fill.
Maximum water depths reach a little over 30 metres in the southeastern corner of territorial waters to the south of Mirs Bay. More commonly, water depths range between 10-15 metres, with a generally flat and featureless muddy seabed that slopes gently southwards. Several deeper channels occur in constricted tidal pathways, for example in Urmston Road, the East Lamma Channel, Lei Yue Mun, Sheung Sz Mun and Lo Chau Mun.
Terrestrial Fauna
The physical and climatic environment of Hong Kong provides woody and grassy habitats for a wide variety of native animal and plant life. Under the pressures of urbanisation, larger animal species are rarely seen, but reptiles, amphibians, birds and many kinds of insects are common.
Most of Hong Kong's countryside is protected by the Forests and Countryside Ordinance, the Wild Animals Protection Ordinance, the Country Parks Ordinance, and the Animals and Plants (Protection of Endangered Species) Ordinance.
One of the most important sites in Hong Kong for wildlife is the Mai Po Marshes. A restricted area under the Wild Animals Protection Ordinance, and managed jointly by the
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