The impact of successive typhoons on sediment transport and topography in the Pearl River Estuary

Successive typhoons can induce cumulative effects on estuarine sediment transport and seabed change, yet their impacts remain poorly understood compared to atmospheric or upper-ocean responses. This study investigates sediment transport and seabed change during two successive typhoons (Hato and Pakhar) in the Pearl River Estuary using the MIKE 3 numerical model. Results reveal that preceding typhoon Hato (peak winds >40 m s⁻¹) triggered widespread erosion, particularly south of Lantau Island (−11.8 mm), while sheltered west shoals retained deposition. In contrast, the weaker subsequent typhoon Pakhar generated a net sediment transport flux 4.5 times pre-typhoon levels - double that of Hato - displacing high sediment concentration zones seaward into deeper waters and mitigating channel sedimentation. Pakhar prolonged erosion in shallow zones and drove significant slope erosion in the West Channel (−6.2 mm), widening the deep channel while shifting the eastern estuary from deposition to net erosion. The combined effects of sediment redistribution and morphological reshaping underscore how typhoon sequences dynamically maintain estuary navigability. These findings offer critical insights for managing sediment in storm-prone areas and emphasize the need to account for cumulative typhoon effects in estuarine management.