That is true, but the river is the only dark ribbon around, so you just stay in the middle. This is one of the most fun approaches to do in the 727 or the 757. One evening many years ago, I was flying the river visual just at dark. It was the 4 of July. As we turned past the Watergate Hotel, the sky erupted in the most amazing display of fireworks I have ever seen. What a show!  :)

Lou