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Hydrology Tools - Flow Accumulation Raster Attribute Table

Question asked by michaeljcullen_PennStateGIS on May 4, 2018
Latest reply on May 4, 2018 by Dan_Patterson

I have 2 DEMs of a portion of Eastern PA in ArcMap:  one is a large area in Pennsylvania another DEM is a smaller clipped polygon within the larger one.  When I try to conduct Hydrology Tool analysis (Fill, Flow, and accumulation) the raster I generate in the TOC for the larger polygon area does not allow me to access an attribute table.  For the flow accumulation raster I selected INTEGER not FLOAT per my lab instructions.  My project requires me to access the table to calculate the number of cells accumulating to a surface area.  I read on another thread that ArcGIS will grey out the attribute table if the raster accumulation tool has too many classes to calculate.  I am attempting to try the process on the smaller polygon to access the attribute table.  What is the class number cutoff that ArcMAP has for prohibiting access to the attribute table?  Is there a threshold area for a polygon after which it becomes disabled?  

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