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How to calculate the right Threshold for flow accumulation using python?

Question asked by apmartincude on Aug 7, 2017

I created a program that generates all the major watersheds that occur on a DEM using a flow accumulation raster. So the only problem that I have, is that my "while loop" depends on the weighted values of the flow accumulation raster. So the condition number I used was 0. This caused my program to create way too many watersheds and most of them I do not need. So I need a threshold number to use as my condition to end the loop. I noticed that I can use the break values that are stored in the classified section in the symbology tab and these values are calculated from a histogram.

This would be an example of a threshold number I would use. Any number below the first break value would give me watersheds that I do not need. What would be the best way to extract this number? I would prefer not to use arcpy.mapping and just have an equation I can use on every Raster to give me a general threshold number in my program. Is there anyway I can use the Maximum,minumum,mean or std value to calculate it using statistics? is there a better threshold number I could use instead? Thank you for your help.