We see them on little year round springs. I think they are to keep debri out and keep the spring flowing. I have also seen one's like that around whiskey sites. would not hurt to look for artifacts or run a metal detector around the area.
Saw your mound post. Probe the humps and see if they are as hard as the flat ground. If they are softer could be a mound or debri piles from ancient loggings. If you have permission a quick test hole will tell you. I did not see any old growth hardwood on them.
Hope you find treasure