Assessment of shoreline alterations using a Digital Shoreline Analysis System: a case study of changes in the...

The aim of our study was to determine the erosion rates and shoreline changes in the Yeşilırmak Delta (Delta) between the oldest available date (1953) before construction of the large-scale dams on the Yeşilırmak River in northern Turkey and 2017. To clearly illustrate the impacts of the dams on the Delta, we investigated the relationship between the dams and shoreline changes. To compute the net shoreline changes and erosion rates over these 64 years, we used a Digital Shoreline Analysis System. To digitize the shoreline changes at the mouth of the Yeşilırmak River, 1:25000-scaled topographic maps from 1957, panchromatic aerial photographs from 1962, a KH-9 Hexagon satellite image from 1980, an Ikonos satellite image from 2002, and a WorldView-2 satellite image from 2017 were used. The west and east sides of the river mouth were divided into six main groups and assessed. Each group included a time series for the shorelines. The groupings were based on the time series. For each group, the net shoreline change (m) was calculated using the net shoreline movement (NSM), and erosion rate (m/year) was calculated using the linear regression rate (LRR). According to NSM computations, net shoreline change varied from - 235.04 to 379.18 m. The greatest evolutions in net shoreline change were observed for group I, with a minimum of - 1101.11 m. According to LRR analysis, the calculated erosion rate varied from - 6.83 to 19.06 m/year. The greatest changes in erosion rate were observed for group II, with a minimum of - 30.63 m/year. There is a close relationship between the construction dates of the dams in the Yeşilırmak Basin and the shoreline changes in the Delta.