Abstract:
Objectives This study aims to investigate the causes and impacts of the levee⁃breach event that occurred in Raoyang River in August 2022, with a particular focus on the role of ground subsidence induced by oil extraction. The analysis includes the spatial-temporal characteristics of land deformation and its influence on flood propagation and inundation extent.
Methods Time series interferometric synthetic aperture radar (InSAR) processing was carried out using ALOS-1 and Sentinel-1 radar images, supplemented by leveling monitoring data, to analyze ground subsidence in the Shuguang Oilfield from March 2007 to November 2021. The pre- and post-breach flood extents were interpreted using Gaofen-3 radar data and a water index-based method. The inundation process and affected land types were further examined. Cumulative ground subsidence was then overlaid with flood inundation areas to assess its impact on levee failure and flood development.
Results The findings reveal that:(1) Oil extraction in the Shuguang Oilfield resulted in an elliptical subsidence funnel, with a maximum annual subsidence rate of -212 mm/a at the center.(2) The Raoyang River flows through this subsidence funnel area, and the flood inundation extent closely overlaps with the subsidence region. The subsidence rate at the breach location reached -150 mm/a.(3) Elevation loss due to ground subsidence compromised the structural integrity of the levee, increasing the risk of pipeline inundation and seepage failure at crossing points. The formed subsidence basin reduced river discharge capacity, facilitating overflow, prolonging water retention, and increasing both the extent and depth of flooding.
Conclusions This study underscores the importance of incorporating ground subsidence into flood risk assessment and flood control planning. The results provide a scientific reference for regional disaster prevention and mitigation strategies, particularly in areas affected by significant human-induced ground deformation.
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