The Fury of Nature: Coping with Landslides
By Dr Clarence Edward Choi, IAS Junior Fellow and Research Assistant Professor of Civil and Environmental Engineering
133 homes were destroyed in the 2014 Hiroshima landslide.
As human development encroaches upon hillsides in densely populated cities and extreme rainfall events occur with increasing frequency due to climate change, the danger posed by landslides will inevitably increase. The real global threat posed by landslides is reflected in the landslide disasters that occurred in Oso, Washington in the United States in 2014, which resulted in 43 deaths and the destruction of 29 homes, and in Hiroshima, Japan, where there were 74 fatalities and 133 homes demolished.
To mitigate this hazardous phenomenon, scientists and engineers must evolve with available smart technology and innovate easy-to-construct and sustainable structural countermeasures to better understand and control landslides.
The Department of Civil and Environmental Engineering of HKUST, under the leadership of Prof Hong K Lo, has recently been awarded a research grant from the Hong Kong Jockey Club Disaster Preparedness and Response Institute to develop a smart Landslide Information System (LIS). More importantly, Prof Charles W W Ng of the department recently obtained a landmark grant of HK$33.25M from the Research Grants Council of Hong Kong for a Theme-based Research Scheme project named “Understanding Debris Flow Mechanisms and Mitigating Risks for Sustainable Hong Kong”.
Choi focuses on investigating the interaction between landslides and structural countermeasures.
Smart Technology and Structural Countermeasures
Prof Y H Wang of the geotechnical group is the pioneer of using machine learning to interpret data and developing sensors to study landslide initiation in the geotechnical group. The LIS, building on his strong foundation, will leverage the use of mobile smartphone technology, including crowdsourcing and GPS technology, to expand the scale and responsiveness of landslide management. It will serve as a decision-making tool for engineers using susceptibility modeling to predict landslide danger under different rainfall scenarios and enable interactive numerical simulations to delineate the extent of a landslide.
Schematic of the 20-m flume model under construction at the Kadoorie Centre in Hong Kong.
The LIS can be further expanded to couple with smart instrumentation on hillsides and barriers, providing real-time landslide data to notify the public and emergency responders of obstructed transportation lines, identifying high-danger areas, facilitating the reporting of landslide incidents, and enhancing the preexisting quality of landslide incident reporting by the public.
By better understanding the complex interaction between landslides and structural countermeasures, engineers can also adopt sustainable, smart, and optimized solutions to protect human lives and infrastructure around the world. The geotechnical group led by Prof Charles W W Ng and Prof Limin Zhang of the department specializes in the physical modeling, specifically flume and centrifuge modeling, of the complex interaction between landslides and structural countermeasures, including an array of baffles, rigid and flexible barriers, slit-dams, and deflectors.
The group is working on the Theme-based Research Scheme project which focuses on the development of world-class facilities to model landslide interaction with barriers at realistic scales, including (i) a new pendulum impact facility in Shenzhen, China; (ii) a new 20-m-long flume model at the Kadoorie Centre, Hong Kong; and (iii) a full-scale 120-m-long flume model in Kunming, China. Prof Jidong Zhao and Prof Gang Wang of the department have also been instrumental in enhancing the current understanding of debris flow through their expertise in numerical modeling and soil dynamics respectively.
The 120-m flume is also a collaborative research project between the Institute of Mountain Hazards and Environment of the Chinese Academy of Sciences and HKUST. It will have a channel width of 10 m to facilitate the installation of prototype barriers and can simulate up to 500 m3 of landslide. These pioneering facilities will be of paramount importance in revealing the fundamental interaction mechanisms between landslides and barriers.
Sustainable Offshore Development
In addition to subaerial landslides (onshore), it is foreseeable that engineers will need to switch gears and place a greater emphasis on submarine (offshore) landslides. As we aggressively expand offshore in search of natural resources, it is expected that the rate of submarine construction adjacent to steep submarine slopes will surge, and offshore structures in these areas will be susceptible to submarine landslides.
Recent local offshore expansion includes an approved wind farm just 9 km east of the Clear Water Bay peninsula and the submarine Pacific Light Cable linking Los Angeles and Hong Kong (announced in 2016). In light of such development, significant research will be required to obtain fundamental scientific knowledge to deal with the threat that submarine landslides pose to offshore structures to provide scientific design recommendations that can prevent costly economic losses from potential damage.
The department is currently developing a new large-scale submarine landslide model to study the impact mechanisms of landslides on oil and gas platforms and pipelines. This offshore landslide research will in turn enhance the application of resilient offshore structures that are capable of withstanding landslide impact while promoting sustainable development.
The current fundamental research is timely because there is a genuine and pressing need for research on the interaction between landslides and structures, whether in subaerial or subaqueous environments. The success of this research will enable scientific recommendations that can guide practitioners to formulate robust landslide preventative measures and to encourage the use of smart and sustainable landslide solutions. This research will benefit densely populated mountainous areas such as Hong Kong, Japan, and Taiwan, and offshore developments around the globe.