Nagare" means "(to) flow" and "Bashi (Hashi)" means "bridge" so it can mean "bridge to flow".
They say it's the longest wooden bridge in Japan. This bridge is designed for the top part to be carried away with the water when the river (KIzu River) is flooded. The top part is tied to the legs with thick wire ropes so that it can be gathered after the flood is over but it still remains unrepaired after the flood in 2010 and the top part is put aside near the legs.
It was still used as an important way to cross the river by local people until then.