Delineating watershed in parking lot with no "stream"

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07-08-2021 08:04 PM
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johntippett
New Contributor

Hi, I ram trying to use my elevation data from a parking lot to delineate the boundaries of the areas draining to different stormwater practices. 

I have a layer of manually collected elevation points.  I processed that in TopoToRaster to get a raster DEM.  I then used the Flow Direction tool to create a D8 flow map, and all the flow arrows look correct.

However, when I use the Watershed tool in Spatial Analyst, I get a line as the output, instead of an area.  I designated a pour point near the lowest spot, and input the D8 flow map. It generates no errors, but it is clearly not giving me the drainage area above that point.

Does the Watershed tool require that I lay a pour point on a designated stream trace?  Is is possible to delineate small catchment boundaries with this tool, on catchments that are just sheet flow?

Or maybe, hopefully, I am just doing something wrong?

The attached image shows the survey points, the raster elevation data, flow directions, and that weird "watershed" output line on the right that goes to the pour point.

Many thanks for any advice/insights,

John

 

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DanPatterson
MVP Esteemed Contributor
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DanPatterson
MVP Esteemed Contributor

Watershed (Spatial Analyst)—ArcGIS Pro | Documentation

Snap Pour Point (Spatial Analyst)—ArcGIS Pro | Documentation

did you try it with flow accumulation and snapping your pour point?


... sort of retired...
johntippett
New Contributor

That was it.  Thank you!

John