A new topological and hierarchical river coding method based on the hydrology structure

Abstract

River network coding is important for hydrological model on the aspects of water cycles simulation, water resources evaluation and extreme hydrological events forecast. However, the existing river network coding methods had several disadvantages, such as, the river network coding structure is too complex to understand, the river network topology is difficult to identify, the river network coding capacity is limited. To overcome the above-mentioned shortcomings, this paper proposed a new topological and hierarchical river coding method based on the river network created by the DEM (Digital Elevation Method) data and ArcGIS software. This method systematically defines the river levels based on the hydrology structure from outlet to source. The river directly flows into the watershed outlet is river L1, the branch of river L1 with a certain catchment area is river L2, the branch of L2 with a certain catchment area is river L3, and so on. Secondly, we proposed a flexible coding scheme that encode the river segments with pure digital numbers hierarchically. Taking the two-digits scheme for example, the L1 river segments are coded with a sequence number, such as [01], [02], [03], […]. The L2 river segments inherit the river code from the L1 stem river segment, add a serial of self-order numbers (01, 02, 03, ……) from the junction to the river source, and become [0101], [0102], [0103], […]. The process of coding the river segments at subsequent level is similar. Finally, this new coding method was programmed in Matlab software, and successfully examined in the Amazon River basin, the world's largest watershed, as a case study. The results show that the new method is competent for easily controlling the river level and river segment density, flexibly adjusting the code digital numbers to fit different basins with abundant or little rivers, easily plotting the topological relationship, automatically encoding by computer program and easily understood. In a word, this study is a useful attempt to create new river network coding method, and it also has positive significance to promote the hydrological simulation research.