On 40 years of landslip prevention by four current and former heads of the Geotechnical Engineering Office
Hong Kong has a hilly terrain with limited flat lands. Most of its buildings and road facilities are constructed along the hillsides. The unique topographical conditions have posed many challenges to the slope safety of Hong Kong. In the early years, the city was prone to landslides, causing injuries or loss of human life and damage to property. The Geotechnical Engineering Office (GEO) was thus set up in 1977, which is currently under the Civil Engineering and Development Department. The GEO has since vigorously implemented the comprehensive Slope Safety System, and landslide risks have been substantially reduced. However, we still need to stay vigilant against the Landslide Demon. For this purpose, I have invited the current and three former heads of the GEO to come together and talk about their work in this aspect.
Frequent landslides in the 1970s
The prolonged, heavy rainstorms on 18 June 1972 led to a series of major landslides on Kotewall Road, Mid-Levels, and in Sau Mau Ping, Kwun Tong. Mr CHAN Kin-sek, Raymond, Head of the GEO between 1998 and 2011, recalled that he lived close to the scene of the Kotewall Road landslide back then and on the night of the incident, he suddenly heard a loud rumbling noise the moment the hillside collapsed. As shown in the historical photographs, the Kotewall Court was completely destroyed by a huge mass of boulders and debris rushing down. The Government mobilised a large rescue team and even the British forces for the rescue and excavation operations. In Sau Mau Ping, tonnes of mud crashed down a hillside and buried a squatter area that left many people dead. Four years later, another landslide tragedy struck Sau Mau Ping again.
Mr CHAN said that the series of major landslides had prompted the Government to recruit engineers from different departments and overseas experts, in the hopes of addressing slope safety problems in a systematic manner. Work included accelerating the stabilisation works on more than 30 fill slope black spots where the soil was loose; and successfully amending legislation to require private slope owners to repair dangerous slopes through the issue of Dangerous Hillside Orders. Mr CHAN Yun-cheung, Head of the GEO between 2011 and 2013, was a graduate engineer in 1976. Mr CHAN said that as people were deeply worried about the frequent disasters, the Government back then had especially trained up a group of personnel for the slope stabilisation works. Moreover, at that time the GEO colleagues were very determined to do their best to prevent disasters and ensure public safety.
The origin of setting up the GEO
After multiple incidents, the Government in 1976 set up an independent review panel comprising international experts to study the landslide problems and recommend solutions. Afterwards, the panel recommended the establishment of a control organisation to regulate hillside development and the design, construction and maintenance of slopes. In 1977, the GEO was established to control the geotechnical works of new or redevelopment projects, and develop strategies for dealing with the large stock of potentially substandard man-made slopes. The designs of new slopes built since then have generally been checked by the GEO to ensure that they conform with the required safety standards. In addition, given that most of the squatter huts that sprang up in the 1980s were on hillsides, the GEO worked with other relevant departments to promote a non-development squatter clearance programme to resettle up to 100 000 people in an orderly manner so that they would not live under the threat of landslides.
Analysing the causes of landslides
For Mr WONG Hok-ning, Head of the GEO between 2013 and 2016, the landslide incidents of the 1970s were the reason why he was drawn to engineering. Mr WONG pointed out that the primary causes of landslides in Hong Kong were typically threefold. Firstly, many existing slopes did not meet the modern safety standards and required stabilisation one after another. Secondly, even with the best engineering techniques, slopes were bound to be affected by uncertain geological factors. Therefore, starting in the 1990s, the GEO had been using soil nails to enhance the robustness of the slope upgrading works. Thirdly, with ever increasing challenges from climate change and extreme rainfall events, natural slopes would be subject to greater pressure. Thus, the public and the practitioners should be constantly reminded to pay more attention.
The public should keep vigilant
Last year marked the 40th anniversary of the establishment of the Slope Safety System. Mr PUN Wai-keung, current Head of the GEO, said that thanks to the efforts of his predecessors, landslide incidents had been considerably reduced in recent years. However, with the numerous hillsides in Hong Kong, it was almost impossible to achieve zero risk. The Government would, therefore, continue to devote resources to slope stabilisation works to keep the risk of landslides at a low level.
The Hong Kong Slope Safety System is a comprehensive, effective slope management system aimed to protect the public from landslide hazards. Its areas of work include upgrading substandard government man-made slopes; ensuring that the new slopes comply with safety standards; mitigating natural terrain landslide hazards; conducting regular inspection and maintenance of government man-made slopes; improving slope safety standards and technology; promoting public awareness on slope safety; and protecting public safety through the Landslip Warning System and landslide emergency services.
Mr PUN cited the example of Typhoon Hato that hit Hong Kong last year, saying that while many praised Hong Kong’s infrastructure for the minor consequences we suffered, it was fortunate that the rainfall was not heavy at the time, and if the torrential rainfall had concentrated in the urban areas, more landslide incidents would possibly have happened. As such, we must be vigilant at all times and made preparations without delay so as to cope with the impact of acute climate change on the slope safety of Hong Kong. We also need to educate the public to stay vigilant so that they would know how to protect themselves in case of emergency.
Slope Safety Summit
In addition, the GEO and the Geotechnical Division of the Hong Kong Institution of Engineers have successfully held the Slope Safety Summit 2017 earlier. I was absolutely delighted to attend this geotechnical event to learn about the efforts made by the department in landslip prevention and mitigation over the years, and to explore the future challenges to the slope safety of Hong Kong and the approaches to tackling them. The summit comprises four discussion sessions on landslide risk management, innovations and technological advances, climate change and public efforts in combating landslide risks. The Chief Executive, the current and former heads of the GEO, and about 260 experts and stakeholders from around the world had been invited to join the summit.
Slope safety is closely related to people’s daily lives and safety. I will find another opportunity to invite our colleagues to introduce the current technological advances in landslip prevention and mitigation. I appreciate the public’s co-operation and their continued support for the work of the GEO in enhancing the slope safety of Hong Kong. I hope that our colleagues will conduct exchanges and collaborate with experts from around the world and continue to upgrade the technology in combating landslide risks for public safety.
4 February, 2018