Integrating chemical and physical factors into delta vulnerability assessment: The role of erosion and diffuse pollution in the Shkumbin River Delta

Coastal deltas are increasingly exposed to combined marine forcing and land-based pollution. This study analyses the relationship between deltaic vulnerability and diffuse contamination in the Shkumbin River Delta, Albania. It introduces an Integrated Coastal Vulnerability Index (ICVI) framework that couples geomorphological, hydrodynamic, and sediment contamination indicators to quantify both physical and chemical vulnerability using multi-source datasets. The assessment is based on official institutional data on sediment quality (Cr, Ni, Cu), seawater quality near the delta, and geomorphological changes, as well as GIS-based spatial analyses for the 2017–2023 period, complemented by satellite imagery. Results indicate that the delta operates not only as a sink for contaminants but also as a secondary source of pollution. Beyond episodic extreme events, continuous coastal erosion (−32.81 ha) drives the remobilization of heavy metals from sediments into the water column, establishing a feedback mechanism between physical instability and chemical dispersion. Cr and Ni HQ values are consistently above 1 (range 2.6–4.5 and 3.5–4.2 respectively). The ICVI (12.2) indicates high vulnerability. The findings highlight the value of integrated multi-source assessments, support catchment–delta management to reduce upstream pressures, stabilize sediment dynamics, and protect the Karavasta Lagoon, Ramsar site.