Assessing the impacts of cyclone ‘Remal’ induced storm surges on soil and water salinization in a coastal region of Bangladesh

The southwestern coastal region of Bangladesh experienced severe environmental disruption due to Cyclone ‘Remal’-induced storm surges, intensifying salinity stress in soil and freshwater systems. The study provides a post-cyclone evaluation of salinization in Sarankhola combining field and laboratory data, geospatial analysis, multivariate analysis, and indices obtained through satellite analyses to measure the extent and spatial variability of the salinity effect. Water quality analysis showed extensive saline intrusion, with average electrical conductivity of 3,273 µS/cm and peak values reaching 10,021 µS/cm, accompanied by elevated chloride (Cl^-, 4250 mg/l) and Total Dissolved Solids (TDS, 6500 mg/l); 13 times higher than WHO’s guideline. Salinity in the soils was widespread, and the average EC was 3,481 µS/cm, with a maximum of 8,486 µS/cm. The disruption of biogeochemical processes was evident from excessive nutrient enrichment, as soil nitrogen (N) and phosphorus (P) concentrations reached 599 mg/kg and 936 mg/kg, respectively. Principal component analysis (PCA) showed salinity parameters (EC, TDS, Na⁺, Cl⁻) explained 83.7% of water variance, while soil salinity and nutrients accounted for 70.8% of variance. Satellite-based indicators derived from Sentinel‑2 imagery, including the Normalized Difference Vegetation Index (NDVI), Normalized Difference Salinity Index (NDSI), and Soil Salinity Index (SI‑ASTER), revealed vegetation loss of 104 km², a 50% expansion of high‑salinity water zones, and a 17.6% rise in very highly saline soils. The results demonstrate that cyclone‑induced storm surges act as a reinforcing mechanism for salinity persistence rather than transient disturbances, providing spatially explicit insights to support coastal management, embankment planning, disaster preparedness, and climate adaptation in vulnerable deltaic regions.