NETWORK TRACING METHOD
Abstract: The Network Tracing Method (NTM) has been developed to determine gridded coarse river networks for modeling large hydrologic systems. For a coarse-resolution grid, the NTM determines the downstream cell of each cell, and the distance along the actual meandering flow paths between them. As opposed to previously developed methods, the NTM uses fine-resolution vector river networks as the source of information of the flow patterns, rather than digital elevation models. The main advantage of using vector river networks as input is that they capture the hydrologic terrain features better than topographic data do, particularly in areas of low topographic relief. The NTM was applied to South America with a grid resolution of 1°×1°, and to the globe with a resolution of 2.815°×2.8125°. Overall, the method captured the flow patterns well. Generated digital river networks and drainage divides showed minor disagreement with those obtained from existing maps, and most of them were consistent with the resolution of the coarse river network. The majority of estimated basin areas were also close to documented values. River lengths calculated with the NTM, however, were consistently underpredicted.
Note: Since the submission of the manuscript to the Journal of the American Water Resources Association (JAWRA), the tool has been further developed to address the problem of underprediction of river lengths. The current code defines the cell reach length as the distance from the cell's exit node to the last point (instead of the first point) in which the stream leaves the downstream cell.
Francisco Olivera, Ph.D., P.E.
Assistant Professor
Department of Civil Engineering
Texas A&M University
Rajeev Raina
Graduate Research Assistant
Department of Civil Engineering
Texas A&M University