Investigation on the seasonal transformation of Tiab estuary’s shoreline using RS and GIS techniques

Estuaries are transition zones between the sea and land, and are constantly affected by tides. These areas are biologically important and sensitive. Tiab estuary, 7 km from away from the coast of Strait of Hormuz, is covered with mangroves and is also used for navigation by small commercial boats. This estuary is facing sedimentation issues nowadays which troubled navigation of vessels. Since the local wind conditions of the area is different seasonally, the influence of this difference on the transformation of the shoreline is considered for the years 2019 and 2020. The wind direction in the area is mainly SSW during summer, while is totally diverse during winter. Sentinel-2 satellite images have been used with similar water-level conditions. Normalized Difference Water Index and K-means algorithm are used for shoreline detection. The results show that the area of the estuary is more than 10 hectares smaller in summertime than in wintertime. The correlation coefficient of the seasonal transformation of the shoreline in 2019 and 2020 is 0.84, which shows that the seasonal transformation was similar in the two years. Shoreline transformation was at most along the curvatures of the river, whether in upstream or downstream. It was however varied between 45 and 200m. Some dissimilarity in shoreline transformation was detected between the two years of study, specifically in upstream of the river, which is suggested to be due to human activities. It is believed that those parts of the estuary with high transformation are subject to permanent transformation in long term.