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.

Urban heat island effects are an increasing challenge for metropolitan areas, especially in regions where climate change increases the frequency of extreme temperatures. The consequences for human health are understood and must be addressed by urban planning. Although many studies currently exist regarding relationships of adaptation measures and urban heat amongst individual single cities, there is little general understanding on how urban development impacts temperature at large scales. In this study we analyze the correlation between urban heat and two indicators of urban morphology: the green spaces and the density of buildings. We hypothesize that the relation between building density, urban green space and urban surface temperature can be quantified openly available techniques of Earth observation. To grant an objective and consistent analysis over the entire country of Vietnam, we use information from different high-resolution imaging satellites. The computation of Pearson correlations across 58 Vietnamese districts confirms the hypothesis, indicating a negative impact of urban green space (-0.217), a positive impact of building density (+0.392) and an even stronger relationship with both indicators combined (+0.435). The findings are discussed with data of three research projects involving the cities of Hồ Chí Minh, Đà Nẵng, and Huế, and interpreted regarding regional differences and implications for urban planning.