Shallow sinkholes
Subtract out the 3m+ count for each cell and what is left are the visual sinkholes with depth less than 3m. Based on 3x3 cells over a topo quad. TN topo is about 60 sq miles, so each cell is about 6.7 sq miles.

150+ shallow sinkholes per cell 50-150 10-50 1-10

See TN sinkholes