Unveiling coastal urban road settlement issues from InSAR monitoring and time-series forecasting: insights from Zhuhai, China

Urban roads connect multiple elements within the city, and the settlement problems of underground railways and above-ground road systems are widespread worldwide. Therefore, we take Zhuhai as an example to investigate the current status and short-term evolution of the coastal city road system settlement. We applied Sentinel-1A and based on the SBAS-InSAR, extracted the settlement information from 2016 to 2019. The results show that the road system settlement has a ‘three-ring’ interval, experiencing four stages: small rise and fall, linear plunge, large rise and fall, and stable settlement. The spatial characteristics of the settlement of highways, national highways, provincial highways, railways, and other types of single roads are manifested in the form of many prominent settlement segments, unequal horizontal extension distances, large vertical settlement variability, and a three-year cumulative settlement of −150~−100 mm at prominent settlement points. Road settlement is strongly influenced by the hydrogeological environment, and the tuning point of road deformation coincides with the timing of extreme meteorological events. The predictive modelling under the existing conditions shows a major settlement of −50 to −30 mm in the coming year, and the impacts will continue to deepen in the following years. This study provides a multi-level perspective on urban road settlement.