How to create an upstream semicircle.

Discussion created by sdaa999 on Feb 24, 2014
Latest reply on Apr 1, 2014 by rfairhur24
Hi all:
There is likely another method to perfor this task this already so I appreciate any help or ideas offered.  I am often asked to find points at a certain distance upstream from a surface water intake.  Rather than look at each buffer around each intake manually, I am looking for a method to generate a semicircle of a known radius with its center at the intake and, once generated, align the semicircle's perpendicular radius to the upstream direction in the NHD flowlines. Then a simple select by location can be used.

Right now, I use a set buffer size on the intake points which gives me a conservative distance on the stream. But, I end up looking at each buffer individually so I can identify if the outfall is upstream or downstream.  So far this is the method I have explored: 1) generate the buffer around the intake, 2) use the Split Tool to generate four quadrants, 3) delete the bottom half of the semicircle, manually rotate the semicircle tothe upstream direction. I tend to look at upwards of 200 intakes; a simpler or automated method would be great!

I have attached a JPG image with my simplified approach.