Digitalizing Disasters to Counter Climate Change
In the face of increasing extreme rainfall events that often trigger further dangers, School of Engineering civil engineers are setting out to develop a pioneering city-scale slope digital twin to boost forecasting, prevention, and mitigation of Hong Kong’s number one natural hazard: landslides.
In early September, Hong Kong experienced its worst flooding for centuries as the last vestiges of Typhoon Haikui swept into the city bringing with them an unprecedented 16-hour black rainstorm alert. Around 600mm of rainfall fell over a 24-hour period, equating to one-quarter of the city’s usual annual total, according to the Hong Kong Observatory. On the southside of Hong Kong Island, it even exceeded 800mm. The weather monitoring body and forecaster also recorded record-breaking hourly rainfall at its headquarters, reaching as high as 158mm at one point.
There were two fatalities and over 140 people sought hospital treatment. The torrential downpours disrupted roads and MTR subway lines, and caused damage to buildings. Of further major concern, over 190 landslides – Hong Kong’s primary natural hazard – were reported, cutting off areas such as Shek O village and causing extensive damage to homes on Redhill Peninsula on Hong Kong Island. However, there were no deaths from the landslides despite Hong Kong’ s densely populated coastal and hilly terrain. And looking at the scale of incidents overall, Prof. ZHANG Limin, a geotechnical specialist in multi-hazard risk management (“where one trigger can cause a lot of hazards”), was quietly relieved. To Prof. Zhang, Head of Department and Chair Professor in Civil and Environmental Engineering, the outcome was an indication that the city’s disaster mitigation measures for flooding and associated landslide risks are having an impact.
In contrast, Prof. Zhang pointed out, the earthquake that happened shortly afterward in Morocco and the torrential rains triggering dam bursts in Libya saw thousands lose their lives and damage so extensive that international emergency assistance had to be requested. Moreover, the after-effects are on-going, with potential disease a major risk and reconstruction amounting to billions of US dollars. In Hong Kong, the day after the major downpour, the city swung back into action. Initial estimates put the cost at around US$100 million. “Though the storm in Libya was smaller than in Hong Kong, you can see the huge difference in the consequences due to preparedness and emergency management,” he said.
Engineering the future, managing risk
Nevertheless, the unexpectedness of the Haikui-related rainstorm, deaths, and deluge of criticism on preparedness that followed showed there is still much more to be done. And as a core member of HKUST’s world-renowned geotechnical research team for close to 25 years, Prof. Zhang is about to contribute, with his timely new research project focused on “Digital Twin-empowered Landslide Emergency Risk Management” that starts in January 2024.
Prof. Zhang has already been heavily involved in driving forward natural disaster and risk management and mitigation methods in Hong Kong, Mainland China, and globally. He believes engineering should not only be concerned with resolving existing problems and improving what already exists. More importantly, it is about “foreseeing and solving future problems”. Which is why he has made multi-risk assessment, risk-based engineering design, and emergency management the focus of his work for the past 15 years, in the process helping to evolve the emerging science.
Looking at the interactions between the risks rather than as individual issues, he and his team have previously established a novel multi-hazard risk analysis framework known as the HKUST five-step method (see box at the end of article). He has worked extensively on risks related to soil mechanics together with his Civil Engineering senior colleague Prof. Charles NG Wang-Wai. Prof. Zhang has also investigated landslide hazard chains triggered by strong earthquakes and associated risk management.
In Hong Kong, the University’s geotechnical engineers often work closely with HKSAR Government departments on a variety of pioneering preventative and mitigation projects. Hong Kong has over 60,000 manmade slopes as well as natural terrain – much of it mountainous – covering 60% of the city’s total land area. While the last landslide-related fatalities occurred in 2008 when two people died on Lantau, some 300 landslides on average still occur annually in Hong Kong, according to the HKSAR Government’s Civil Engineering and Development Department. Moreover, as statistics indicate (see chart below) and the black rainstorm demonstrated, extreme rainfall – one of the key triggers – is increasing in both intensity and frequency in Hong Kong.
Impact of climate change: extreme rainfall in Hong Kong
Increasing intensity and frequency of extreme rainfall in Hong Kong due to climate change. (Updated chart, based on original by Dr. C. T. Lee)
World-leading city-scale slope digital twin
Thus, in his “Digital Twin” project, Prof. Zhang is set to further assist policymakers and the community in better forecasting and emergency response, leveraging the data analysis and technological advances opened up by the digital era, in particular AI, remote sensing, and augmented/virtual reality. One project goal is to deliver the world’s first comprehensive and versatile city-scale slope digital twin to sense, simulate, and visualize landslide hazard processes in order to coordinate how to respond. Prof. Zhang is also seeking to create a new model for managing hazard emergency risks that covers the “human response” aspect of landslide emergency risk management. This will be achieved through devising a digital twin-empowered common operating platform with an augmented reality environment for interactive decision-making, emergency management, as well as immersive public education.