Google earth engine based approach for coastal water monitoring: a case study of the southern shore of caspian sea

Coastal regions are important, sensitive ecological systems and are also significant from an economic point of view as they are used for tourism, fishing, aquaculture, and recreation. An attempt was made to focus on the Caspian Sea including the southern shore of it, Mazandaran province, Iran using the Google earth engine platform. This study for the first time assesses the shoreline changes over 33 years and sea surface salinity, by using Landsat 5 TM and Landsat 9 OLI data acquired from the coastal region of the southern Caspian Sea. The coastal zone features were delineated using Landsat 5 TM and Landsat 9 OLI data respectively from 1988 and 2022. A manual identification technique was used for coastline extraction and detection. The advances in shoreline position were mainly detected over these 33 years in 6 points, as a result of breakwaters which are constructed to prevent erosion and the structural buildings such as recreational piers or wharves. The SSS expression was implemented on the datasets of pre-monsoon and post-monsoon seasons. The estimated SSS was in the range of 3-20 PSU. The higher range of SSS was spatially along the nearshore with a maximum of about 9-20 PSU in the pre-monsoon image. The SSS derived from the post-monsoon dataset illustrated a lower amount of SSS in some places nearshore which was due to the mixing of freshwater from river discharge and Indian monsoon precipitation in summer 2022. The obtained SSS was validated by in-situ measurement in 20 stations and the R2 value of 0.92 showed a strong correlation between observed and satellite-derived SSS products.