How about model a section of your layout that is experiencing a flood?
It should be easy to do: just rooftops sticking out of the water, the water brown and opaque (so you don't have to model the details underneath), a few boats rescuing folks sitting on their roofs...
If it was a violent flood, cars and debris up in the trees.
The intrepid rail crew pushing their train through the waters (creating a wake).
I remember years ago Model Railroader had a scene in their along the line pictures of a module where there was a flood and a farmer was trying to evacuate some of his hogs to higher ground. It was a module on the Midwest Valley Modelers layout. It was pretty neat you could see the top half of the barn and the farmer with a couple of his hogs in a little motor boat.


