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Problem with DEM mosaic in watershed delineation project

Question asked by jdacord0 on Jul 29, 2019
Latest reply on Jul 29, 2019 by MBoucher21

I am trying to delineate nearly 700 watersheds from Stormwater outflow points on relatively small order streams. I have found that 1-meter and 30-meter DEMs are either too fine or too coarse of a scale for this work. I was given multiple 10-meter .tif files to use for the DEM.

-I've used the 'Mosaic to New Raster' tool which has an overlapping effect on the raster imagery that makes it unusable (image 1). My best guess is that the mosaic tool is taking the "black" areas, which should have a null value, and giving them a very low numeric value. When the mosaic tool is used, it addresses the top most layer and uses it's value over the layers below it.

- To get around this, I tried the 'Raster Catelog To Raster Dataset' tool to see if it would behave differently and it appears to do about the same as above. 
-Images 1 and 2 show the overlapping effects and the "black areas" that have extremely low values


I'm not quite sure how to overcome this issue. Is there a tool like 'Mosaic to New Raster' that will ignore those low values? Or is there a way to edit those values in each Raster layer?