And speaking of spillways

This is the spillway at the tip of the island in the Cher at Saint-Aignan. I think it was built to create a small reservoir in the southern branch. That water provided the power to operate a gristmill adjacent to the bridge (it closed long ago and subsequently burned down).

Big tree trunks and limbs can get stranded on the spillway.

In summer, or whenever the river is low, the spillway can be completely exposed and dry; there's not enough water to spill over. The north branch of the river can look like a series of puddles when that happens. Take a look at this post from six years ago. In flood conditions, the spillway can be completely submerged (along with parts of the island) as both branches of the river flow at the same level.