Linking land subsidence to soil types within Hue city in Central Vietnam

Kurzfassung

Coastal areas of Southeast Asia are progressively threatened by flooding as a consequence of more frequent precipitation extremes and rising sea levels. Especially urban areas are affected by flood risk which is additionally increased by surface subsidence related to building activities and groundwater extraction. However, the severity of subsidence as well as its triggers and environmental interrelations are only little understood. This study measures surface subsidence for Hue city by using persistent scatterer radar interferometry (PS-InSAR). A series of 53 images acquired by the Sentinel-1 radar satellite between 2018 and 2019 was analyzed to reliably retrieve surface changes at the millimeter scale. The overall displacement ranges between -25 and +10 millimeters per year. Its spatial distribution was then compared to the extent of different soil types in the study area to conduct an analysis of variance (ANOVA). The results confirmed a significant difference between the soil types with Plinthic Acrisols as the soil type having the largest negative average surface velocity. Possible triggers are the intrusion of slack water from the surrounding rice cultivation areas and construction activities which lead to increasing weight and soil compaction. The findings shall raise awareness for the topic and underline the demand for further research.