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Why are the displayed delineations different than the delineation I've downloaded?

By StreamStats

The StreamStats application uses a generalization process to reduce the resolution of a basin for display purposes. Rest assured the computations are calculated on the full-resolution delineation.

The StreamStats application uses the flow direction raster (a product of the hydro-conditioned DEM) to delineate a basin. Depending on the size of the basin that has been delineated, this raster can have upwards of 1,000 vertices which can significantly delay the display of the delineation in the application. Thus, the application uses a generalization process to reduce the number of vertices for display purposes only. All basin characteristics and flow estimate computations are calculated using the full resolution delineation. The full resolution delineation is also provided in the download functionality.