Development and application of a new algorithm for automated pit removal for grid DEMs

Pits and flat surfaces in raster digital elevation models (DEMs) have been unavoidable obstacles in the extraction of drainage networks. A new automatic method of "pits filling" is presented that eliminates all pits and flat areas simultaneously. Spatially distributed elevation increments of pits are computed. Based on this new approach, drainage networks of more than 10 medium- to large-sized basins have been extracted, including the Mekong River and the Yangtze River. Overlaying the computed drainage networks onto the digitized actual stream networks, good visual consistency was obtained. Besides, the calculated flow pattern over a flat area has been shown to be convergent. The results indicate that the proposed algorithm is easy to use and applicable to DEMs with a wide range of terrain relief and resolution.