Reverse Watershed?

[DevinMcCoy]

I am using Arc Pro 2.8 and am trying to figure out how to predict where a stream of lava will flow. I found a guide online on how to run a watershed but after repeated attempts realized it was doing the opposite of what I need. https://support.esri.com/en/technical-article/000023169 I need to predict what the flow will be, but unfortunately this predicts where flow will come from. Are there any tools that can predict where liquid will flow from a designated point?

[curtvprice · Accepted solution]

The Optimal Path As Raster tool can be used to 'trace downstream' using the same flow direction raster used to make watersheds.

The optimal path created can be a flow path based on D8 flow direction. To generate an optimal path in this way, use a D8 flow direction raster as input for the Input back direction or flow direction raster parameter. You also need to supply an Input distance accumulation raster value; the Input distance accumulation raster value is not used to determine the path. Whether you use a constant raster or a digital elevation model (DEM), the path will be the same; only an attribute value on the path will vary. See the Flow Direction tool documentation for more information on D8 flow direction rasters.