Determination of Temporal Changes in the Sinuosity and Braiding Characteristics of the Kizilirmak River, Turkey

Abstract

In this study, the pattern of the approximately 1,300-km-long Kizilirmak River was recreated in a geographic information system (GIS) environment using data obtained from Landsat TM/ETM+/OLI satellite images from 1987, 2000, and 2013. The temporal changes in the sinuosity and braiding characteristics of the river were determined for the periods 1987-2000 and 2000-13. The right and left shorelines of the Kizilirmak River and the shorelines of islands and bars within the river channel were extracted automatically from the satellite images by integrating the normalized difference water index (NDWI) and modified normalized difference water index (MNDWI). The data required for measuring the sinuosity and braiding characteristics were obtained by evaluating the shorelines in the GIS environment. The braiding index (BI), braid-channel ratio (B), and braiding ratio (BR) were used to determine the braiding of the river, and the sinuosity index was used to determine the sinuosity of the river. The Kizilirmak River was divided into 21 analyzed sections based on the locations of dams. The sinuosity decreased in 15 sections in 1987-2000 and 2000-13. The BI, B, and BR values decreased in 11 sections in 1987-2000 and in 9 sections in 2000-13. Sinuosity and braiding both decreased in most of the sections downstream of dams; these sections were often subject to uncontrolled sand and gravel extractions.