A novel algorithm with heuristic information for extracting drainage networks from raster DEMs

Abstract. Extracting drainage networks from raster DEMs is a necessary requirement in almost all hydrological and environmental analyses and determining surface water flow direction is a fundamental problem. In a raster environment, surface water flow direction of each cell can be directed to the neighboring cell with the steepest downslope drop (The basic D8, deterministic eight-neighbour method), which is inadequate for routing flow over pits and flats. Several improved algorithms are proposed to find the outlet of pits and flats, which typically use entirely different procedures for processing pits and flats. Being different from others, this paper presents a new method to route flow through the pits and flats by searching for the outlet using the heuristic information to compensate inadequate searching information of other methods. Heuristic information can reveal the general trend of the DEM and help the proposed algorithm find the outlet of pits and flats accurately. Furthermore, the proposed algorithm can handle pits and flats effectively in one procedure. This new algorithm is implemented in Pascal and experiments are carried out on actual DEM data. It can be seen from the comparison of the drainage networks generated by the proposed algorithm and ArcGIS 9.2, the proposed algorithm with heuristic information can get a closer match result with existing river networks and avoid the generation of the unrealistic parallel drainage lines, unreal drainage lines and spurious terrain features.