Stream network creation and watershed definition by using digital elevation model for Samsun, Turkey

In this study, drainage networks, boundaries of watershed and sub-basins were determined by using Geographical Information Systems (GIS). Digital Elevation Model (DEM), Triangulated Irregular Network model (TIN) and satellite images were used to compare stream beds in currently available database and drainage networks created in this study. DEM used to produce stream flows and watersheds was produced from topographical maps with a scale of 1/50.000 and resolution of 20 m. Stream networks with different details were obtained based on the number of minimum cell to create stream network. It was observed that a regular and realistic stream network was not able to be created over the sites with slopes less than 4% and over the sites around the dams and lakes. The TIN model and satellite data revealed a more complex morphology for channels derived from the DEM and created network is in better agreement with the actual cases than those derived from conventional methods. Following the stream network creation, watersheds were defined and classified in 3 sub-groups. There were 368 river basins (covering more than 1000 ha area), 347 micro watershed (4001000 ha) and 550 sub-watershed (200-385 ha) in research site.