I like the concept, I think that the map just needs a couple of tweaks to show better the mechanics of what and how.

Perhaps more mountains to the south and north of the chute area? I like the idea of the overflow into the marsh, can picture a brackish marsh with crocodiles and the like feeding on the fish that get flushed through. Or the pod of dolphin that ride the passage for fun.

Generic maps like this are great.

BOB