San Antonio, Texas, has a quite famous River Walk. Dallas, Texas has been attempting to finalize a very large plan to do with the Trinity River (and Trinity Forest, etc.)

My back yard has a creek in it and there is a trail back there. But I don't suppose that helps you (but we really like it!)

The National Park Service has several sites in the east along the old canals. The C & O Canal, for one. http://www.nps.gov/choh/.

SRS