Quadtree and Sub-Grid Sampling FAQ: Difference between revisions

When the SGS parameters are being processed, every cell face will store its own curve of flow area versus elevation. TUFLOW doesn’t actually know the location in the cell or along the cell face where the lower elevations are, it just parametrises that they exist. As such, SGS isn't a grid within the model grid. It allows water to flow from low point to low point within the same cell even if there is higher point in between them. It automatically defines the minimum flow paths.<br>

If the DEM is fine enough, SGS can preserve the gully along the cells without using any gully line. In such case using a gully line may overestimate the width of the flow path as it makes the entire cell and face flat. This effect will get more pronounced when cell sizes are increased, e.g. wider unrealistic flow path is created when gully lines are still used in the model.<br>

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