HKDSE Geography/E1/Human Activities and the Landscape
Opportunities and risks brought by geology to the urban development in Hong Kong
Opportunities
• granite is extracted as construction materials, e.g. granite blocks used in rock armour, aggregates used in cement pavements
• regolith from igneous rock areas, e.g. Tai Tong and Sai Kung were used as rock fill in reclamation projects in the past
• developing rock cavern in igneous bedrocks for housing undesirable facilities, e.g. sewage treatment plants. This releases urban land for housing development
Risks
• high peaks and rugged relief associated with extrusive rocks are not suitable for urban development. This leads to shortage of flatland for development
• deep weathering profile on granitic slopes means thick layer of loose materials. This increases the risk of landslides which threaten urban areas
• tors on granitic slopes may collapse in rockfalls. This may hinder road transport and threaten settlements
• engineering measures used to prevent landslides in urban areas increase the costs of development
Several human activities shape Hong Kong's landscape.
Urbanisation edit
Urbanisation has modified the landscape:
- Trees are removed and sometimes, new trees are planted in the area
- The area is covered with impermeable layer like cement
- Slopes are cut and filled if it hampers urban development. The slope is steepened.
Mining edit
To practice quarrying and mining:
- Slopes are cut, surface rocks are removed and depressions are created on the ground
- For opencast mining, vast areas of vegetation are removed
Reclamation edit
Reclamation have changed Hong Kong' landscape in a number of ways.
Reclamation along the coasts, including bays and shallow waterfronts, has the following effects:
- The coastline is shorter and straighter.
- Harbours are narrowed, most notably Victoria Harbour.
- Bays and shallow seas are buried, destroying their marine ecosystems (Yam O, Junk Bay)
- Islands disappear as they are connected to reclaimed land (Stonecutters Island)
In addition, because of the extraction of reclamation materials, the seabed may be deepened and land levelled.
Similarly, natural lowlands have been reclaimed. The effects:
- New towns and low-density residential areas have replaced floodplains, wetlands, farmland and fish ponds (e.g. Nam Sang Wai -> Tin Shui Wai and Fairview Park)
- Tombolos are raised by reclamation for settlement (Cheung Chau)
- Natural vegetation is removed and the area is covered with cement
|
Reclamation in Hong Kong
|
Landfills edit
Landfills also affect the landscape:
- Valleys were filled and land was raised
- A cap of clay seals the waste
- Layers of soil cover the clay cap for landscape restoration
All old landfills have been closed and replaced by three strategic landfills. The old landfills have often been landscaped to create green zones, further changing the landscape.
|
Landfill restoration
(Source) |
Reservoir Creation edit
To create reservoirs, several landscapes occur:
- Water inlets are dammed by connecting islands and headlands, then draining away seawater (e.g. High Island Reservoir and Plover Cove Reservoir)
- Valleys are dammed and flooded
- Channels are dammed (e.g. Shing Mun River was cut off from the upper course by Shing Mun Reservoir)
- Slopes are afforested to reduce sediments brought by runoff
Flood Prevention edit
To prevent flooding, several landscape changes have been made:
- The lowland was raised
- Winding rivers were straightened, widened and channelised to reduce silting. This increases their capacity to hold flood water and drain it to the sea. (e.g. Ng Tung river)
- The natural ecosystem is irreversibly damaged
Developing Natural and Agricultural Landscapes edit
People have developed natural landscapes for various purposes.
- Natural vegetation is replaced by selected species of grass in golf courses
- Swampy areas are dammed and dredged for fish ponds
- Trees are cleared for agriculture
- Slopes are terraced on sloping farmland