USGS Method B-9135-00

Suspended sediment concentration (SSC) information on the coastal waters is necessary for understanding and management of the estuarine environment. It serves as an indicator of coastal erosion and deposition.

It is challenging for a macro-tidal estuary like the Hugli with a complex hydrodynamic condition and depth variations to estimate suspended sediment concentration by field observations only. In the present study, we estimated suspended sediment concentration at different depths of the lower Hugli estuary in the post-monsoon season by using Sentinel-2 satellite data. Since SSC is highest in the monsoon months, the image of October 22, 2019 was selected, which was the earliest available cloud-free data. Furthermore, about forty water samples were collected from different depths on the same date and time of the satellite pass for ground truth verification and data calibration. An empirical multivariate regression algorithm was used to demarcate the SSC zones in the image and correlate them with depth variations.

MIKE-21 hydrodynamic model was also used to assess the spatial pattern of sediment flow in the Hugli river estuary. Remote sensing and GIS have proved to be a useful framework to estimate the SSC of any water column’s surface layer to overcome the limitation posed by the field measurements alone.