Research on extraction of stream network based on digital elevation models

Three algorithms of automated extraction of stream network based on digital elevation models (DEMs) are introduced and reviewed. They are the moving windows algorithm, the flow of water over terrain algorithm and a valley line finding algorithm. The flow of water over terrain algorithm has become very widely used because it has a hydrological basis, can produce a continuous stream network, can be linked with distributed parameter models. Then the advantages and disadvantages of these three algorithms are compared and analyzed. Then the main problems are pointed out and discussed. Three main problems of flow of water over terrain algorithm: (a) the problem of positioning the ends of streams; (b) the problem of drainage direction assignment in flat areas and pits; (b) the problem of distinction between extracted stream network and natural stream network are discussed emphatically. Finally the future intensive research fields are pointed out according to the problems.