Deformation monitoring and spatiotemporal analysis of Hekoucun water conservancy project using SBAS-InSAR

Abstract

[Objective] The Hekoucun water conservancy project plays a vital role in flood control and water resource utilization, and its safety is of great significance to the local socioeconomic development. Therefore, timely monitoring of its deformation trend is necessary to identify and mitigate potential safety hazards. [Methods] Compared with traditional deformation monitoring method, Interferometric Synthetic Aperture Radar(InSAR) offered advantages such as all-day and all-weather operation, large-scale high-precision coverage, and high spatiotemporal resolution. SBAS-InSAR was employed to extract time-series deformation information of the Hekoucun water conservancy project area from October 2017 to December 2022. The accuracy was validated using leveling measurements and compared with PS-InSAR result. The spatiotemporal characteristics and influencing factors of deformation were analyzed in combination with geographic data. [Results] The results showed that the deformation extraction accuracy of SBAS was 5.21 mm, while that of PSI was 8.07 mm. The density of SBAS deformation points in the study area was 2.49 times that of PSI. The deformation rate in the Hekoucun reservoir area ranged from-8.6 to 3.2 mm/a. Two funnel-shaped settlement zones were identified: the dam-front square(about 45 mm settlement) and the flood-control warehouse(about 50 mm settlement), with the latter showing accelerated settlement after heavy rainfall in July 2021. The deformation rate of the Hekoucun dam ranged from-4 to 2 mm/a, with the maximum settlement of about 15 mm over five years. The central part of the dam crest showed the greatest settlement, with periodic fluctuations. The dam crest deformation was positively correlated with rainfall(correlation coefficients all above 0.5) and negatively correlated with water level(average correlation of-0.32). [Conclusion] The results indicate that SBAS is more effective than PSI in monitoring surface deformation in water conservancy project areas. The deformation of the dam front square and flood-control warehouse is mainly influenced by rainfall. The overall deformation characteristics of the dam show greater settlement at the center than at the shoulders, and greater settlement at the dam crest than at the dam base. Additionally, higher water levels lead to increased settlement at the dam crest. Dam deformation shows periodic fluctuations of relatively small magnitude and currently does not compromise dam safety. The findings provide scientific support for the safe operation of the Hekoucun water conservancy project and serve as a reference for deformation monitoring in other water conservancy projects.

Keywords

time-series InSAR / water conservancy project / earth-rock dam / deformation monitoring / spatiotemporal characteristics / deformation / settlement / rainfall