I am attempting to obtain the rainfall erosivity "R" factor for the RUSLE Soil Loss equation using rainfall PRISM 30 year history data. I have both monthly and annual data that comes into ArcMap as rasters, so in total I have 13 raster images in Arc Map. In the images below, I have placed the 12 monthly rainfall rasters into model builder, to convert the rasters to points, interpolate them using the Spline tool, and Extract by Mask, in order to get them ready for use in the Fournier Index. enter image description here Above shows the process of getting them through each tool in Arc Map. (seen in second image below). ![enter image description here][2] Once I have the "Extract" rasters (image 2), I will place them into the Fournier Index formula, which in turn will give me the R factor for the RUSLE. The problem with this, is that when I finish the model builder equation, I am left with the monthly averages all having the same raster value. enter image description here

So In turn, when I plug them into the R factor Fournier equation, I'm left with irrelevant data. Does anyone know the solution to this? I'm pretty new to stack exchange, so I apologize if I've asked the question incorrectly.


1) I think you could clean up your model a lot by using the Raster Iterator (see image below, also incorporating points 2 & 3).

2) The Clip tool is used for vector type files, not rasters. I think you mean to use Extract by Mask where you now have Clip in your first image.

3) In your second image, why do you extract by mask if you have already "clipped" all of your rasters to the same shape (Denver Watershed). Are you trying to extract an average rainfall of the area? Since it is already "clipped" to the watershed, you could simply look at the statistics for the output raster to get the average of all the cells.

enter image description here

  • Thanks for getting back to me so quickly! I originally clipped the image because the original PRISM file was too large to work with otherwise. The main goal was to interpolate the data using the spline tool. I will try and use this model! thank you! – Geordi Alm Mar 16 '15 at 16:04
  • The "Extract by Mask" in my model is doing the same thing that you describe as "clipping" I think. You are on the right track in that reducing the size of the raster to the extent you need for your analysis in the beginning of your process is a good idea to reduce processing time/resources as you go. – Leo Mar 16 '15 at 16:48
  • @GeordiAlm, if this helped you, can you please upvote and/or mark as answered? Thanks. Otherwise, maybe clarify what you're still looking for. – Leo Mar 17 '15 at 12:36

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