Abstract
This study develops an integrated modeling framework to assess the transport and coastal risks of floating debris. The approach is applied to the Pearl River Estuary (PRE), one of the largest and most populated coastal areas in the world. The framework is built on an enhanced Lagrangian particle-tracking model (TrackMPD), incorporating Stokes drift for wave-induced transport, site-specific horizontal dispersion coefficients, and a probabilistic beaching module based on coastline topology. Representative hydrodynamic conditions were derived using K-means clustering of multi-decadal data, driving ensemble simulations from five source domains, including Zhu Jiang (ZJ), West Estuary (WE), East Estuary (EE), Hong Kong (HK), and Da Peng (DP) domains. A composite hazard-vulnerability index, quantifying pollution exposure and ecological-socioeconomic sensitivity, was applied for risk assessment. The analysis revealed distinct, region-specific risk patterns shaped by local topography and seasonal hydrodynamic features, with pollution impacts predominantly localized to the coastlines near each source domain. High-risk zones for floating debris largely overlapped with ecologically sensitive areas such as nature reserves and aquaculture sites. Beaching dynamics, validated against marine refuse data from Hong Kong beaches, showed patterns strongly dependent on coastline type and source domain, leading to elevated risk along the eastern Hong Kong and western PRE coasts. The comprehensive framework effectively predicts the spatial and seasonal distribution of floating debris, providing a validated tool for supporting targeted regional pollution management in complex coastal systems.