This bridge isn't pointless. It's flooded. It could have been built higher, but why? During a flood it's a bridge to nowhere. It could have been built lower, but then boats wouldn't be able to pass under it. All very sensible.
And artful. Someone thought about how the bridge could look during a flood, and took the opportunity to make some art. During a flood there's something to catch the eye, and make the eye and mind pay attention in the way that is the core of art. I love that.