AUTOMATED CHANNEL ORDERING AND NODE INDEXING FOR RASTER CHANNEL NETWORKS

A numerical algorithm is proposed for automated interpretation of chan nel networks from raster images, indexing of network nodes, and orderi ng of channels by the Strahler method. Channel ordering and node index ing is fundamental to the automation of flow-routing management in dis tributed hydrologic models and morphometric evaluation of channel-netw ork structure. The node index numbers can also serve to link network n odes to corresponding tabulated attributes of network channels. The pr oposed algorithm uses a two-step approach: first, the raster image of the network is interpreted and a channel attribute table is created; s econd, the network nodes are indexed based only on the network connect ivity information contained in the channel attribute table. The use of attribute information in the second step eliminates a repeat of the t ime consuming cell-by-cell interpretations of the network raster image . In addition to the general case of nodes with two upstream inflows, the algorithm also handles complex nodes (nodes with more than two ups tream inflows) which are rare under natural conditions, but more Frequ ent in raster networks. The final product of the presented algorithm i s a table of channel orders and node indices derived from raster image s of channel networks. (C) 1998 Elsevier Science Ltd. All rights reser ved.