The ground clutter appears to be covering the entire terrain, including the smaller ponds near towns and Tank Town area of NDisles. There is a frame rate drop also which may be associated with the same issue.
I was testing several Graphic Detail options and removed the environmental settings that I have been using up until now. Then I also decided to test several resolution settings and discovered a problem where AHAlpha will change the resolution of the game, but when closing will not change the resolution of the desktop back to its original setting. So, if I am running a 4k desktop and then change the game resolution to 2560 x 1600 the game may close normally, or crash, but may also leave the desktop resolution at 2560 x 1600.
Also, there is an ahalpha (32 bit) background process that remains after the game is closed.
EDIT: Maybe related to that last issue. If the game crashes then I have to reboot or the frame rate will remain at about 1/2 its normal level. So, the ground clutter is obviously not the problem there. If the game closes normally there is no background process remaining.