State-accredited scholar puts SAR on safe track

Hong Kong geotechnical expert's multi-hazard prevention team is helping the city deal with landslides and severe flooding caused by torrential rain. Xi Tianqi reports from Hong Kong.

Aonce-in-a-century rainstorm tore through a wide swathe of the Guangdong-Hong Kong-Macao Greater Bay Area on Sept 7 last year, forcing Hong Kong to hoist the black rainstorm signal - the highest of a three-tiered rainstorm warning system - for more than 16 hours, with roads inundated, cars submerged and trees uprooted.

The torrential downpour broke the Hong Kong Special Administrative Region's one-hour precipitation record set in 1884, with 158.1 millimeters of rain, triggering about 500 sizable landslides in the following days although no landslide casualties were reported.

The widespread landslides posed a great threat to residents' lives, recalls Zhang Limin, head of the Digital Cities and Smart Hazard Mitigation Laboratory at the Hong Kong University of Science and Technology.

Zhang is leading a team in developing a multi-hazard prevention digital-twin system to strengthen the city's predictive, early warning and emergency coordination capabilities against landslides induced by rains and earthquakes.

Using data from government departments, including the Geotechnical Engineering Office and the Hong Kong Observatory, the experts have drawn up high precision maps with details of hillsides, landforms and buildings across the city with precipitation and earthquake data.

The system also relies on scientific eyes from outer space - the HKUST-FYBB#1 satellite - and other remote sensing technologies to monitor deformation and displacement hazards of the natural terrain and more than 60,000 artificial slopes in Hong Kong. Data collected by the sensors is shared with Zhang's system.

With the data in hand, Zhang believes the system can perceive and simulate natural disasters like landslides and flooding, identifying locations where they're likely to occur.

Zhang's bid to mitigate secondary disasters paid off after last year's record rainfall as the number and locations of landslides and flooding that occurred between Sept 7 and 12 closely matched his system's projections. The simulation results covering the HKSAR and Shenzhen have formed part of the post-event retrospective analysis of the impact of the black-signal storm on the Guangdong-Hong Kong-Macao Greater Bay Area.

Zhang, who heads the HKUST's Department of Civil and Environmental Engineering, is the first Hong Kong scholar to win the National Engineering Award - the nation's highest honor for the profession.

As a renowned expert in slope safety, landslide risk management and geotechnical engineering, Zhang joined the HKUST in 1998. Last year, his team received a HK$74 million ($9.49 million) grant from the Research Grant Council to develop a citywide disaster-prevention system.

The system, apart from helping researchers to perceive, simulate and demonstrate landslide disaster processes, can also report the results to emergency response departments for prompt action to mitigate potential risks. Such capacity plays a crucial role in dealing with natural disasters, says Zhang.

In case of landslides or severe flooding, researchers can be notified by sensors installed on slopes or other key locations, enabling them to plan anti-disaster action in computers. "Where a landslide would possibly occur and how it would affect nearby areas are what we need to simulate," he explains, adding that his team can also predict societal responses in order to coordinate with disaster response measures.

According to the geotechnical expert, rainfall, like many other natural disasters, is only the first domino in the chain. The consequential hazards can, sometimes, cause greater damage to residents and infrastructure.

Zhang's team was involved in the reconstruction of Wenchuan, Sichuan province, a region that was almost been wiped off the map by a magnitude 8 earthquake in 2008. The reconstruction work was particularly challenging due to numerous difficulties posed by secondary disasters, he says.

Like other regions in the country, the HKSAR government played an active part in Wenchuan's reconstruction, contributing HK$10 billion to rebuild infrastructure and supporting those affected by the disaster from 2008 to 2016.

Zhang recalled that the massive temblor brought down numerous buildings, triggering widespread landslides. Loose materials from landslips turned into huge pools of debris during the rain, becoming deadly torrents that caused significant damage.

By 2010, most of the main roads in the quake-stricken areas had been rebuilt, including some funded by the HKSAR. However, following a heavy downpour, a road constructed with Hong Kong funds was destroyed. Many rebuilt roads in Wenchuan have repeatedly been washed away by mudslides or heavy rain, according to Zhang.

Drawing on experience

Experience gathered from earthquakes and other natural calamities have enriched Zhang's understanding of the mechanism of disaster chains. The simulation software developed based on data collected from previous projects has placed his team at the forefront of those preventing natural disasters in the country.

Zhang and his laboratory now focus on addressing the complex geological disaster chain in the Guangdong-Hong Kong-Macao Greater Bay Area, covering torrential rain, storm surges and flooding.

"We need to inspect every location's unique natural condition, including meteorology, geology, hydrology and the surrounding urban environment. All these require serious on-site investigation," says Zhang, adding that artificial intelligence technologies are helpful in conducting surveys and monitoring situations in different locations.

Predictive and early warning systems can only address some of the challenges facing public as disasters would inevitably occur, he explains, saying that it's crucial to implement engineering and non-engineering measures to cushion any potential effects.

If the timing of disasters could be accurately predicted, buildings with stronger anti-disaster capabilities could be constructed, says Zhang, and many measures can be taken before disasters occur, such as better urban planning and more stringent safety regulations. Non-engineering measures include emergency response plans under various scenarios.

Public education is also essential. Zhang and his team have met primary and secondary students to raise their awareness of natural disasters and give them knowledge on how to respond.

Laying foundations

In 2021 and 2023, Zhang led researchers in conducting scientific investigations along the route of the yet-to-be-completed Sichuan-Xizang Railway. Through on-site inspections of geological hazards along the train line, they've gained a visual understanding of the occurrence and evolution processes of glacier debris flows and glacial lake outburst floods in the southeastern Xizang autonomous region.

The research has laid the foundation for the design, construction and risk assessment of the Sichuan-Xizang Railway - a 1,900-kilometer rail line due to be completed by 2032 connecting Sichuan's provincial capital Chengdu, and Lhasa, capital of the Xizang autonomous region - as well as hydropower projects along the rail route.

Zhang says the Xizang site investigations offer Hong Kong a channel to use its expertise in landslide risk prevention and control to help in national initiatives.

Zhang saw a wealth of opportunities Hong Kong could offer in 1998, when he got back from the United States, saying he was deeply impressed by the establishment of the Hong Kong University of Science and Technology.

He recalls that the university's staff recruitment campaign showed its intention to create a pioneering higher educational institution in science and technology, and the favorable research conditions offered were attractive.

Having lived in Hong Kong for more than 25 years, the mainland-born scientist considers the city his second home. He believes the SAR enjoys advantages in scientific and technological innovation, including abundant professionals, substantial funding, internationalization and an entrepreneurial culture of innovation. While technologies may have specific areas of expertise, science itself shares commonalities.

Zhang suggests that Hong Kong research teams seize the chance to participate in the country's major national science and technology programs. While many national projects were not open to Hong Kong scientists in the past, the barriers have gradually been removed in recent years, giving Hong Kong scientists more space for development.

He hopes the central authorities will include scientists from the Hong Kong and Macao SARs in national research projects to allow them deeper participation. He also thanked the central authorities for facilitating the flow of research funds from the Chinese mainland to Hong Kong.

Zhang is excited by the influx of mainland and foreign professionals into Hong Kong under the SAR government's talent attraction programs in the past two years, but says retaining them will be a challenge and that the government should create more opportunities to persuade them to stay for longer.

Earlier this year, Zhang's team used the disaster-prevention system to help a Hong Kong power company implement protective measures at its substations ahead of the rainy season.

Chief Executive John Lee Ka-chiu said the government has learned from what had happened during last year's extreme weather conditions and is studying and planning various improvement measures.

Interdepartmental meetings have been held to review the experience gathered and discuss strengthening measures to deal with a higher frequency of adverse weather conditions to avert potential risks.

The SAR government announced a series of new measures earlier this month to beef up emergency response capabilities under extreme weather, including a comprehensive inspection of all artificial slopes, improvement to drainage systems and the installation of more sensors in areas at high risk of flooding.

Zhang recognizes Hong Kong's efforts in preventing and controlling landslide risks, but says the city needs to deal with more geological disaster challenges in the changing climate. He hopes his studies and the digital disaster-prevention system developed help Hong Kong go further in this direction.

Zhang Limin biography

• PhD in geotechnical engineering, Chengdu University of Science and Technology

• Director of the Digital Cities and Smart Hazard Mitigation Laboratory

• Associate director of the GREAT Smart Cities Institute

• Head of the Department of Civil and Environmental Engineering at the Hong Kong University of Science and Technology

• First scholar from a higher education institution in Hong Kong to receive the National Engineering Award — the nation’s highest honor in engineering

Research fields

• Climate information and impact assessment

• Dam safety

• Debris flows

• Foundations and piles

• Geotechnical engineering

• Landslide risks

• Slopes