The complex vortex structure causes navigation-obstructing obstruction in the fluctuating backwater area of the Three Gorges.However,the dynamic evolution mechanism of the vortex structure is unclear,making it difficult to effectively guide ship navigation.To address this issue,a high-precision unmanned aerial vehicle (UAV) image acquisition system is built to carry out the observation of the vortex structure in the Hujiatan Reach.An image processing technology for surface vortex structure identification and tracking is proposed,and the spatiotemporal evolution characteristics of the vortex structure in the variable return water area are quantitatively analyzed.The core area of the vortex is identified through gray-scale conversion,binarization segmentation and morphological detection methods,and its geometric characteristics are quantified by the equivalent circle method.Combined with the inter-frame displacement method,the dynamic evolution parameters between frames of the vortex structure are extracted.The results show that the vortex structure exhibits a distinct three-stage evolution characteristic during its motion process.There is a significant positive correlation between the radius of the vortex structure and its movement velocity,and this correlation shows stage dependence:in the expansion stage,the correlation is weak due to the influence of external factors;in the contraction stage,the correlation is strong,dominated by internal hydrodynamicmechanisms.Furthermore,the growth rate jump point during the rapid expansion period of the vortex structure's movement and migration process can be regarded as a key node for the pre-adjustment of the ship's course,providing theoretical support for the subsequent discovery of the influence of the vortex structure in the fluctuating backwater area of the Three Gorges on ship movement.