Sappa Creek is a stream in the central Great Plains of North America. A tributary of the Republican River, it flows for 150 miles through the American states of Kansas and Nebraska. Sappa Creek originates in the High Plains of northwest Kansas. It is formed by the confluence of North Fork Sappa Creek and South Fork Sappa Creek located roughly 3.5 …Sappa Creek is a stream in the central Great Plains of North America. A tributary of the Republican River, it flows for 150 miles through the American states of Kansas and Nebraska. Sappa Creek originates in the High Plains of northwest Kansas. It is formed by the confluence of North Fork Sappa Creek and South Fork Sappa Creek located roughly 3.5 miles southwest of Oberlin, Kansas in Decatur County. From there, in flows generally northeast into south-central Nebraska. In west-central Harlan County, Nebraska, it joins the Republican River.