Abstract
An algorithm to extract drainage networks by using digital elevation model (DEM) was proposed. It has three characteristic points, i.e., pre-specification of inland water areas, shortest path for outlet in flat areas, and restriction of filling level for depression areas. The algorithm was applied to DEM with 50m grid size covering Tohoku district of Japan, which has about 35 million inland grid points. The extracted drainage networks were relevantly compatible to those described in 1/25, 000 topographical maps, and also included a lot of finer drainages in rugged areas. The processing time by using HP9000/C3000 workstation system, however, was about 25 minutes.
