Analysis and risk evaluation of current land subsidence in Ningbo City

In response to evaluating the current status and assessing the risk assessment requirements of land subsidence in Ningbo City, the characteristics of land subsidence in recent years were analyzed using InSAR remote sensing monitoring data and subsidence point monitoring data from 2017 to 2020. Based on this analysis, a land subsidence risk assessment system has been developed, primarily consisting of six evaluation factors, including ground elevation, susceptibility to subsidence, cumulative ground subsidence, subsidence rate, urban population density, and the proportion of construction land usage. The susceptibility to subsidence is a comprehensive evaluation factor that takes into account geological conditions, hydrogeological conditions, and the impact of human activities. The results of the land subsidence risk assessment indicate that there are no high-risk susceptibility zones for land subsidence in Ningbo City. Medium and low-risk susceptibility zones are primarily associated with factors such as the thick layers of the Holocene soft soil, historical excessive groundwater extraction, localized high-intensity urban development, and coastal land reclamation projects within the region. Finally, the areas were categorized into medium-risk, low-risk, and risk prevention zones, along with corresponding control recommendations for land subsidence risk management.