Abstract
In Ho Chi Minh City (HCMC), Vietnam, though at present flooding is merely a recurring nuisance, there is increasing concern that a combination of impending climate change and rapid urbanization will significantly exacerbate the situation. Given the significant measures taken in HCMC to reduce groundwater extraction and sea-level rise (SLR) inundation since the most recent subsidence studies, we aim to update and contribute to the subsidence information of HCMC with continuous temporal coverage from 2017 to 2019. In this study, we use Persistent Scatterer Interferometry (PSI) with Copernicus Sentinel-1 data and open source tools to determine current subsidence rates within the urban center of HCMC. Additionally, the scalability of this method and use of freely accessible data allows for continuous updating and monitoring of this high-vulnerability region. The observed average subsidence rates were 3.3 mm per year with a maximum local subsidence of 5.3 cm per year. These results largely align with findings of previous studies and reflect similar spatial distributed subsidence patterns. Inundation risk awareness is enhanced by not only continued improved subsidence analysis, but also incorporating latest advancements in Digital Elevation Model (DEM) accuracy. This study compares local differences between traditionally used AW3D30 DEM with the CoastalDEM. Our findings indicate that although we identify lower than previously accepted elevations in the urban core, that stabilization of subsidence is observed in this same region.
Highlights
Coastal regions are popular settlement areas, most notably river deltas
The presence of some observed uplift may suggest that aquifer-system deformation resulting from groundwater withdrawals in Ho Chi Minh City (HCMC) has remained in the elastic range of stress at least in the urban core and north east districts
This study showed how openly available Sentinel-1 data can be used to retrieve precise and up to date vertical displacements for the metropolitan area of HCMC
Summary
Coastal regions are popular settlement areas, most notably river deltas. Globally, over 500 million people live on deltas, of which many are increasingly exposed to the hazards that arise from rapid urbanization, climate change, and sea level rise [1,2]. Coastal cities of Asia-Pacific (APAC) are home to the greatest number of people, over 151 million, who currently reside on land at risk of permanent inundation by 2100 [4] For many of these cities, rapid urbanization and significant vulnerability to climate change has led to extensive undertakings by local governing bodies and institutions to address related and pressing issues such as subsidence. Persistent Scatterer Interferometry (PSI) has proven effective in urban areas because of the stable phase information returning from man-made structures and artificial surfaces, such as buildings, roads or other coherent point targets [15,16] It has been successfully applied in Vietnam, including Hanoi [17,18], Hué [19], Ben Tre province [20] and Ho Chi Minh City [21]. The latest InSAR studies published used data from 2010 or earlier [21,22]
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