Landslip mitigation Hong Kong

Year:1977

Duration:41 years and counting

Cost:£2bn

Country: Hong Kong

What did this project achieve?

Come up with a way of stopping landslide disasters after heavy rains in Hong Kong

Hong Kong has a population of over 7 million people in a small land area – around 1,100km2. Much of this is natural terrain and there has always been a shortage of flat land to build on.

Hong Kong’s economy expanded rapidly from the 1960s and homes were needed for the growing population of workers.

As a result, there was a period of largely unregulated urban hillside development to meet the demand for living accommodation. About 40,000 man-made slopes were created around this time.

This explosion of building on hilly terrain combined with high levels of seasonal rainfall meant many of Hong Kong’s urban slopes were unsafe and liable to collapse. More than 480 people have died in landslides since the 1940s.

In 1977 the Hong Kong government started a slope retro-fitting project – known as the landslip preventative measures (LPM) programme. The LPM scheme aimed to reduce risks from landslides by upgrading man-made slopes to modern safety standards.

The government launched the landslip prevention and mitigation (LPMit) programme in 2010.

LPMit builds on the success of the LPM scheme and aims to upgrade 150 substandard slopes every year.

Difference the landslip programme has made

The LPMit scheme has reduced the chance of landslides in Hong Kong by 75%.

The upgraded slopes are designed to be stronger against Hong Kong’s often heavy rainstorms and could also help mitigate the impact of climate change.

How the work was done

Engineers working on the LPMit programme generally use a technique known as ‘soil nailing’ to make slopes safer.

Developed by a working group at the Hong Kong Institute of Engineers (HKIE), soil nailing sees steel bars driven through the looser top layer of soil – known as fill material – into the more solid ground beneath.

A grid-like structure of steel – known as a surface grillage – connects the heads of the soil nails together and keeps them in place.

Soil nailing can mean less disruption than other methods which could involve major excavation works such as cutting back a slope or digging out earth to replace it with denser soil.

The technique can also make it easier to upgrade a slope when a project team is working at height or close to buildings or roads.

More than 6,000 sub-standard slopes have been upgraded as part of the LPMit programme.

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Worst deluge in 83 years hits Hong Kong… flats crash in a day of disaster; 78 squatter huts inundated in big landslide.

The South China Morning Post

on 2 landslides that killed 138 people, 19 June 1972.

Fascinating facts

Hong Kong is part of China and one of the most densely populated areas in the world.

Hong Kong was a British colony until 1997, when it was returned to China. The ownership of the islands and surrounding territories had been part of a deal signed between China and Britain in 1842 following a trade war.

While Hong Kong was a British territory the Hong Kong police force was effectively a division of London’s Metropolitan police.

People who made it happen

  • Client: The government of Hong Kong
  • Around 1,000 engineers, contractors and consultants have worked on the LPMit scheme.

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