Research on Typical Estuarine Sedimentation Characteristics: A Case Study of the Liaohe Estuary Wetland

The Liaohe Estuary, characterized by Asia’s largest reed marshes and diverse wetland types, provides critical habitats for endangered bird species and performs vital ecological functions, making it a representative international wetland. Tidal flats, as essential components of estuarine wetlands, dissipate wave energy and stabilize shorelines. However, due to their peripheral location within estuarine systems, quantitative monitoring and risk assessment of the Liaohe Estuary tidal flat remain constrained. In this study, 187 cloud-filtered Landsat TM/ETM+/OLI scenes acquired between 2001 and 2021 were integrated with a waterline-derived DEM framework to quantify sedimentation dynamics in the Liaohe Estuary wetland. During the study period, the tidal-flat area exhibited a declining trend, while interannual surface elevations generally ranged from +2.18 to −1.61 m. The mean surface elevation increased by 25.33 cm, accompanied by a mean slope increase of 0.11‰; the average sedimentation rate was 1.27 cm yr−1, with a net depositional volume of 0.51 km3, indicating an overall depositional regime. Moreover, mean elevation displayed a statistically significant upward trend (Kendall’s tau = 0.636, p = 0.0057), corroborating the significant rise in tidal-flat elevation from 2001 to 2021. The coexistence of elevation gain and spatial contraction suggests limited geomorphic resilience and a shrinking spatial extent of the tidal flat. The proposed approach provides a robust framework for long-term monitoring and supports the formulation of quantifiable sustainability targets for coastal management in the Liaohe Estuary.