Inundation frequency correction method for mapping multi-temporal tidal flat topography integrating Sentinel-1 and ICESat-2 data

Remote sensing monitoring of tidal flat topographic changes is essential for analyzing the tidal flat evolution and coastal stability. However, the inter-annual inconsistency of inundation frequency limited the capacity of multi-temporal tidal flat topography monitoring. To address this limitation, this study proposed an inundation frequency correction method for mapping multi-temporal tidal flat topography and applied the method in Yueqing Bay, China, during 2017 ~ 2022. Specifically, we quantified the impact of tidal level distribution characteristics on inundation frequency. It was found that the discrepancies in tidal distribution characteristics of time-series satellite image collections from different periods led to the inter-annual inconsistency of inundation frequency. Thereafter, we corrected inundation frequency by aligning the tidal level distribution characteristics of time-series satellite image collections with the actual condition. Accuracy evaluation results showed that the method significantly improved the consistency of multi-temporal inundation frequency, increasing the determination coefficients (R2) of the inundation frequency for adjacent periods from 0.71 ~ 0.81 to 0.89 ~ 0.93. Thereafter, a uniform inundation frequency-elevation correlation model was established to map the multi-temporal tidal flat topography. After correction, the topography Root Mean Square Error (RMSE) validated by in-situ data in 2019 reduced from 0.47 m to 0.43 m, and the model’s multi-temporal mapping RMSE (validated by ICESat-2 data during 2021 ~ 2022) reduced from 0.66 m to 0.45 m. The proposed method effectively improved the topography multi-temporal mapping capability. On this basis, we accurately identified the tidal flat accretion and erosion process caused by human activities. The results suggested that our method could be extended to more regions to provide time-series topography data for analyzing tidal flat evolution.