The Riverscape Analysis Project (RAP) is a web-based GIS Decision Support System that will assist in salmon conservation across the North Pacific Rim (NPR), based upon a robust classification (typology) of rivers and river habitats which is aimed at conserving the existing potential production of salmon in the context of the ocean domains influencing the rivers and salmon that spawn and rear in them. Funding for this project was provided by the Gordon and Betty Moore Foundation.
We developed a hierarchical Dominant River Tracing (DRT) algorithm for automated extraction and spatial upscaling of basin flow directions and river networks using fine scale hydrography inputs (e.g. flow direction, river networks and flow accumulation). In contrast with previous upscaling methods, the DRT algorithm utilizes information on global and local drainage patterns from baseline fine scale hydrography to determine upscaled flow directions and other critical variables including upscaled basin area, basin shape and river lengths. The DRT algorithm preserves the original baseline hierarchical drainage structure by tracing each entire flow path from headwater to river mouth at fine scale while prioritizing successively higher order basins and rivers for tracing. We applied the algorithm to produce a series of global hydrography data sets from 1/16° to 2˚spatial scales in two geographic projections (WGS84 and Lambert azimuthal equal area). The DRT results were evaluated against other alternative upscaling methods and hydrography datasets for continental USA and global domains. These results show favorable DRT upscaling performance in preserving baseline fine scale river network information, including: (1) improved, automated extraction of flow directions and river networks at any spatial scale without the need for manual correction; (2) consistency of river network, basin shape, basin area, river length and basin internal drainage structure between upscaled and baseline fine scale hydrography; (3) performance largely independent of spatial scale, geographic region and projection. The results of this study include an initial set of DRT upscaled global hydrography maps derived from HYDRO1K baseline fine scale hydrography inputs
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