Surface Subsidence in Urbanized Coastal Areas: PSI Methods Based on Sentinel-1 for Ho Chi Minh City

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.

A Flood Risk Framework Capturing the Seasonality of and Dependence Between Rainfall and Sea Levels—An Application to Ho Chi Minh City, Vietnam

“…Important sources of nonstationarities should be considered when applying our framework to future risk projections. First, HCMC experiences high subsidence rates between 20 until 60 mm/year close to the rivers (Duffy et al., 2020; Minh et al., 2015). A simplified way to include this would be to assume spatially uniform subsidence, even though this might result in an underestimation or overestimation of flood impacts.…”

Review of satellite radar interferometry for subsidence analysis

“…Extensometers measurements, providing convenient ground control along columns of soil, have been also used (30 times) to constrain the interferometry results (Buckley et al, 2003;Calderhead et al, 2010;Tessitore et al, 2016) being aware that, depending on the depths of the extensometer bases relative to the compacting layer, the extensometers may measure only a partial amount of the total subsidence. Some authors investigated the relationship between spatial patterns of ground deformation and topographic changes by using DEM, built with stereo images using space-borne optical photogrammetry (Pu et al, 2021) or the space-based radar such as the Coastal-DEM (Duffy et al, 2020). This latter has the great advantage, with respect to other prevalent DEMs, to have a reduced vertical bias in low-lying, coastal densely populated areas, where accurate elevation data is vital for accurate inundation risk assessment.…”

Anpassung an Überschwemmungen in südostasiatischen Megastädten – Was kann der Privatsektor leisten?

“…Der durch Landsenkungen verursachte relative Meeresspiegel steigt jährlich um mindestens 4 cm in Jakarta bzw. im Durchschnitt um 3,3 mm in HCMC (Bott 2020;Duffy et al 2020). Obgleich nationale und lokale Behörden in diesen Hotspots mit internationaler Unterstützung (u. a. durch die Weltbank und die japanische Entwicklungszusammenarbeit) Fortschritte beim Überschwemmungsschutz erzielt haben, sind die bislang durchgeführten Maßnahmen angesichts der prognostizierten Klimaauswirkungen unzureichend.…”