Prof. Alex Hay-Man Ng
Guangdong University of Technology, China
Title: Comprehensive Assessment of Land Subsidence in the West Pearl River Delta using Combined InSAR Time Series, Land Use, and Geological Data
Abstract:
The
West Pearl River Delta (WPRD) region is experiencing land subsidence due to the
combined effect of natural and anthropogenic factors. This study investigates
the concern of land subsidence in the region, attributed to rapid urbanization
and tremendous population growth over the past few decades. A comprehensive
subsidence analysis of sixty-seven Sentinel-1 images, acquired between 2016 and
2021, using the persistent scatterer interferometry technique (PSI), has been
conducted to monitor and reveal the ground subsidence characteristics in the
WPRD.
The
findings indicate a range of overall vertical deformation velocities in the
WPRD, varying between -70 mm/year and 10 mm/year. Notably, three distinct
subsidence bowls have been identified in the study area, including Gaolan
Island in Zhuhai, the junction area of Zhuhai and Zhongshan, and the junction
area of Zhongshan and Jiangmen. Spatial-temporal subsidence patterns have been
analyzed, revealing that ground subsidence is predominantly observed in
Quaternary deposits and closely related to sediment thickness. This association
underscores the significant contribution of soft soil consolidation to land
subsidence in the region.
Furthermore,
land use maps for 2016 and 2021 were generated utilizing Landsat-8 images to
examine the relationship between land subsidence and land use. The analysis
reveals that rapid subsidence occurs primarily in aquaculture, urban, and
agricultural areas, with higher rates observed in regions undergoing
substantial land use conversions driven by human activities. To predict
subsidence rates, a Random Forest Regression (RFR) model incorporating
influential factors such as soft soil thickness, groundwater exploitation, land
use, elevation, and strata lithology was employed. The RFR model demonstrated
favorable predictive performance (R2 = 0.631, RMSE = 2.7 mm/year).
Importance assessment of these influencing factors based on the RFR algorithm
revealed that soft soil thickness, elevation, groundwater exploitation, strata
lithology, and landcover type are the most significant factors affecting
subsidence.
Moreover,
the applicability of geological data and land-use history for land subsidence
prediction was demonstrated through the utilization of the RFR algorithm.
Finally, a comprehensive land subsidence risk assessment was conducted by combining
information on land subsidence hazard and vulnerability. The results identified
high-risk regions and sub-high-risk regions of subsidence, covering an area of
17.93 km2 and 123.52 km2, respectively, which account for
0.4% and 2.77% of the total evaluated region. These regions are primarily
concentrated in Zhuhai City, Zhongshan City, and Jiangmen City.
This study provides crucial
insights and serves as a valuable reference for the prevention and management
of land subsidence in the West Pearl River Delta region.
Biography:
Prof. Ng is a Professor in
Guangdong University of Technology. He completed his Bachelor's and Master's
degree in Electrical Engineering in University of New South Wales, Australia,
and continued his doctoral study in Department of Surveying and Spatial Information
System. In June 2011, he obtained his doctoral degree. From November 2010
to December 2016, he worked in University of New South Wales in the Department
of Surveying and Spatial Information System and Department of Civil and
Environmental Engineering as a research associate and was mainly engaged in
satellite remote sensing image analysis method and its application, InSAR
algorithm and software development, ground subsidence monitoring and modeling,
image classification. In 2017, he joined Guangdong University of Technology and
has since been working there.
Prof. Ng has published more than
80 articles in international journals and conferences. In addition, he has
presided over and participated in a number of national and provincial research
projects. His research papers have received more than 900 citations according
to the Web of Science database, resulting in an h-index of 18. Prof. Ng has
been actively engaged in various research projects. He has led or participated
in research projects supported by the National Natural Science Foundation of
China, the Discovery Fund of the Australian Research Council, the Natural
Science Foundation of Guangdong Province, etc. In addition to his research and
teaching achievements, Prof. Ng serves as Associate Editor for the SCI journal
"Frontiers in Earth Science" and as an editorial board member for the
journal "Remote Sensing."