Close a trade route? Now that's a new idea. Maybe the next Pharaoh type game could have this as an option. Back to the subject: The most obvious way is to disconnect the dock entirely. Perhaps you could delete the dock, but maybe all those annoying "no working dock" messages would appear.
One more thing: How come you guys hate Sawu? Isn't it a nice place? What's wrong with it?
BTW after what baltic has said about Sawu being challenging, I have a funny feeling that in the near future, one competition will be using this map.
Da Pharaoher
From the Field of Reeds