We substract out the digital sinkholes (3m+) from the visual count, and what remains are visual sinkholes with depth less than 3m. Click on cell for quadname and sinkhole count. Based on 3x3 cells over a topo quad. TN topo is about 60 sq miles, so each cell is about 6.7 sq miles.

100+ 50-100 10-50 1-10

See TN sinkholes