Basic problem: I have two layers, a layer containing river basin outlines and a layer of wetland outlines and types.

I need to make a buffer around one river basin, and then create 100 random points within a single type of wetlnad within the river basin + buffer.

I guess the first problem is how to create a buffer around just one river basin when the layer contains many (they do not overlap). The second problem is that I need to isolate just one wetland type within the total area contained by the buffer (so that river basin + the buffer around it), so that I can make random points inside that wetland type.

I've been fighting with trying to make a buffer around just that one river basin for days, I'm sure it's possible but I've never used buffers before. How do I do this?

Thanks in advance for any help!

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    What GIS software do you have access to?
    – Aaron
    Commented Apr 25, 2013 at 21:24

1 Answer 1


For an ArcGIS solution, you can accomplish this analysis with a combination of selections, an intersect and via the create random points tool.

  • Use a select tool to identify your basin. Make sure it is highlighted (usually in light blue)

enter image description here

  • Run the Buffer tool on the "selected" river basin layer. To combine the buffer and the selected feature, use Merge and Dissolve, as required. Make sure the basin is still selected.
  • Perform a SQL search to select the particular wetlands you want. A query similar to "wetlands" = 'riparian' should be added to the Select by Attributes search.

enter image description here

  • Add the buffered riparian basin and the selected wetlands layer to the Intersect tool.
  • Now you have a polygon that represents the particular area you are interested in based on two layers.
  • Use the Create Random Points tool. Make sure to use the intersected polygon as your constraining featureclass--this will allow points to be randomly generated only within the polygon.

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