New insights into the 2020 Sardoba dam failure in Uzbekistan from Earth observation

On 1 May 2020, the Sardoba Reservoir in Uzbekistan breached its western wall, and the uncontrolled release of water caused casualties, environmental damages and economic losses. We investigate the dam failure based on three sets of Earth observation data, including: (i) satellite altimetry products, i.e., ICESat-2 data, with the aim of understanding the topographic features in the study area; (ii) multi-geometry Sentinel-1 SAR data to retrieve the pre-failure deformation along the vertical and horizontal east-west directions between 2017 and 2020; (iii) optical images from Sentinel-2 satellites and Global Precipitation Measurement (GPM) products, which are involved in exploring the environmental status before the failure. We analyse the possible causes of the collapse in terms of both physical and human factors. The differential settlement of ∼60 mm revealed by InSAR at the failure section is a sign of internal erosion through the embankment, which is the physical factor contributing to the failure. The opportunity to prevent the collapse were missed due to the human factor of ignorance brought by limitations of the conventional monitoring methods. Neither ground observations nor satellite-based GPM products show extreme precipitation in the region, ruling out the likelihood of rainfall-induced overtopping. The settlement rate of the embankment shows no decaying trend, indicating that the dam is undergoing the primary consolidation phase of total settlement. Maximum settlement of ∼270 mm (∼0.8% of the dam height) has happened on the north bank since the reservoir impoundment, which should raise concern in future monitoring and surveillance. The results reveal that InSAR can discern the failure precursor by detecting surface motion, and that the deformation signals can help to warn of risks and avoid dam damage. We recommend InSAR deformation monitoring be included in future safety programs, providing detailed deformation and resisting risks of ignorance.