Here's a clip about the reversing falls in Alna:

Farther downstream it (Sheepscot River) drops over the Head Tide Dam to mix with the incoming tide, flowing by the delightful antique houses of Alna. After meandering through Sheepscot Village, with its reversing falls, the river slides through Newcastle and bustling Wiscasset, once one of the busiest ports in North America.

We used to sing a verse of lamentation about Head Tide:

I lost my maid in Head Tide...

Cheerily,
Charley Noble