What is the impact of "mountain view houses" in Hong Kong?, Black rainstorm

The Hong Kong Observatory issued a black rainstorm warning signal late on the 7th night, causing flooding in many parts of Hong Kong. The headquarters of the Hong Kong Observatory recorded an hourly rainfall of 158.1 millimeters from 11pm to midnight on the 7th, which is the highest record since records began in 1884.

Due to terrain limitations, many tall buildings in Hong Kong are built on the mountain, and houses located on the mountaintop often sell for higher prices due to their spacious views. Under the "century rainstorm", does the house built on the mountain need to worry about natural disasters such as debris flow? What impact will housing prices be affected by?

A house built on a mountain

Public information shows that about 60% of the land in Hong Kong has steep natural slopes. Mount Tai Ping, located on Hong Kong Island, has an elevation of 552 meters and is the highest mountain in Hong Kong. Due to its high terrain and wide field of view, Victoria Harbour has always been favored by Hong Kong tycoons, with many executives from multinational banks and companies gathering here.

According to public media reports, Xu Jiayin, Chairman of the Board of Directors of Evergrande Group, previously owned three villas on the Peak Boulevard, namely Block B, Block C, and Block E, with a market value of HKD 700 million to HKD 1 billion.

Shi Wenxin, Director of the South and Mid Levels Business of Lijia Property, introduced to China News Service that, taking Taiping Mountain as an example, most of the houses built on the top of the mountain are Western style houses with a unit price ranging from HKD 40000 to HKD 100000 per foot, while the houses at the foot of the mountain and Mid Levels are mostly layered buildings with lower prices. The Mid Levels in Central are conveniently located and enjoy the beautiful scenery of Victoria Harbour, with prices ranging from over 20000 to 70000 Hong Kong dollars per foot, depending on factors such as landscape and layout; Shanjiao mainly refers to residential units in the urban area, with a unit price of approximately HKD 10000 to HKD 20000 per foot in the Wan Chai and Central Upper Ring areas.

Shi Wenxin said that people in Hong Kong have been living halfway up the mountain since a hundred years ago, and the retaining walls on the mountain are very strong. There have been no major accidents in recent decades. There is no need to worry about safety when living in the mountains, but traffic will still be affected in rainstorm weather.

On the 8th, the reporter visited near Wan Chai on Hong Kong Island and saw that multiple sidewalks and road surfaces were cracked, underground pipelines were exposed, and the ground was scattered with some gravel and tree branches. Some shop staff in low-lying areas have been cleaning up the accumulated water in the shops since early morning. On the Morrison Mountain Road, nearby businesses are spontaneously clearing the branches, leaves, and gravel covering the roadside drainage outlet to allow the accumulated water to be drained.

How to prevent landslides?

Hong Kong has many mountains and few plains, with an average annual rainfall of over 2000 millimeters. The website of the Hong Kong Observatory states in its introduction to the climate of Hong Kong that approximately 80% of the rainfall in Hong Kong is recorded from May to September, with June and August usually being the months with the highest rainfall. On average, 30 tropical cyclones form annually in the western North Pacific, East China Sea, and South China Sea. If the center of a tropical cyclone moves closer to Hong Kong, the wind will increase and there may be heavy rain in a wide area. The heavy rain brought by tropical cyclones can last for several days, causing landslides and flooding, and sometimes causing more damage than strong winds.

Despite being mountainous and rainy, and being frequented by typhoons all year round, Hong Kong has had very few casualties in the past decade. Against the backdrop of frequent extreme weather, what experiences can it draw from?

According to public information, Hong Kong has also experienced multiple serious disasters in the past. For example, in 1976, a fill slope in Xiu Mao Ping, Kowloon collapsed in heavy rain, causing 18 deaths. In this situation, Hong Kong Geotechnical Engineering was declared established in 1977 to develop an overall slope safety strategy and reduce the risk of landslides on slopes.

In 2010, the Hong Kong Department of Soil and Water Engineering launched the "Long term Prevention and Control of Landslide" plan, which generally adopts risk mitigation measures to deal with natural mountain slope landslide disasters, such as building concrete debris dams and flexible protective nets under the slopes to prevent collapsed debris from entering residential buildings or roads and causing casualties.

In the eyes of the outside world, one of the most successful projects of the Hong Kong Geotechnical Engineering Department since its establishment over 40 years ago is the Landslide Warning System. In the event of a rainstorm in Hong Kong, the Geotechnical Engineering Department will issue a landslip alarm to remind the public that there may be a danger of landslip. It will constantly broadcast alarm messages on radio and television stations, suggesting that the public should take preventive measures, such as staying away from steep slopes and canceling unnecessary journeys, and advising motorists to avoid going to hillside areas or roads with landslip warning signals.

According to data disclosed by the Hong Kong Department of Soil Engineering, research and engineering expenses for preventing and controlling landslides in 2022 amounted to approximately 1 billion yuan. A total of 158 government artificial slopes have been consolidated in this area, safety screening studies have been conducted on 100 private artificial slopes, and risk mitigation projects have been carried out on 36 natural slopes.

However, with the increasing frequency of extreme weather, the possibility of landslides and mudslides still exists. According to Hong Kong Wen Wei Po, Professor Wu Hongwei from the Department of Civil and Environmental Engineering at the Faculty of Engineering at the Hong Kong University of Science and Technology has conducted research on slope safety and provided three plans to cope with extreme weather. Firstly, by using artificial intelligence and machine learning, the heavy rain forecast period can be advanced from 3 hours to 6 hours ago, and the precise range can be reduced; Secondly, establish a comprehensive warning system for extreme weather and landslides; Thirdly, develop design specifications for multi-layer flexible protective barriers.

How to choose a house in mountainous areas?

In November 2022, a reference bulletin published on the official website of the Hong Kong Geotechnical Engineering Agency cited the research results, pointing out that although the slope safety system of Hong Kong has successfully reduced the overall landslide risk of Hong Kong to a "reasonable and feasible minimum level", if the rainstorm in June 2008 resumed and occurred in the densely populated urban area of Hong Kong, hundreds of serious landslide events would be triggered, especially the debris flow on natural slopes.

"Landslip may block roads, damage buildings and affect other important facilities, and it cannot be ruled out that a large-scale and serious landslip accident may cause many casualties and major economic losses. What's more, if extreme rainstorm occurs in Hong Kong around the world in recent years, it may cause thousands of serious landslip events." The above research results also said.

This typhoon has also caused flooding in several cities in Guangdong Province, including Guangzhou and Shenzhen, with severe flooding in some urban areas. Xie Yifeng, the director of the China Urban Real Estate Research Institute based in Guangzhou, said in an interview with China News Service that Guangzhou and Shenzhen have been significantly affected by disasters, with more cases of houses and cars being submerged in water. In recent years, whether in southern or northern China, the frequency of extreme weather has been increasing, which has also sounded the alarm for residents to purchase properties.

Xie Yifeng said that Hong Kong is mainly mountainous, so when purchasing property, it is important to pay attention to the surrounding terrain and try to buy in areas with higher terrain and less prone to waterlogging; If there are steep slopes nearby, in order to prevent extreme weather and rainwater from flowing back, it is also advisable to choose high-rise buildings. For cities like Guangzhou and Shenzhen with flat urban terrain, priority should be given to areas with relatively developed drainage systems and a certain distance from rivers or beaches.

Zhao Xiuchi, Dean of the Beijing Tianjin Hebei Real Estate Research Institute at Capital University of Economics and Trade, previously told China News Service that safety is the first consideration when purchasing a house, and caution should be exercised when purchasing properties in disaster prone areas such as floods. If homeowners purchase housing in relevant areas, it is recommended to consider purchasing property insurance for the property and reducing potential risk losses through insurance mechanisms.

However, Shi Wenxin believes that extreme weather is only temporary. In 2018, Typhoon Mangkhut dealt a heavy blow to Hong Kong, causing seawater to pour into residential buildings in Xinghua Estate on the eastern coast of Hong Kong Island. Currently, its housing prices have not been affected.