Meanders
"Only liquids cause meanders"
No, no, and no again!
Meanders are NOT uniquely diagnostic evidence of the subaerial flow of liquid water.
They ARE evidence of flow of a dense fluid underneath a less dense one, but the fluid may be a gas, a slurry, a liquid or whatever.
They ARE evidence of repeated or prolonged flow down the same channel.
They ARE evidence for a momentum-dominated flow.