This is a remake of an old scenario I made with the first OTTD build with rivers, then I overwrote it with another scenario when saving, but I had a screenshot, so I was able to remake it
I used no grfs (the ones you can see are loaded after saving the scenario to make it a little more nice to view on the screenshot)
The scale sort of puts a limit on the overall effect. What might be nice to see some day is a "swamp
" or "marsh" tile that would incur some additional cost to build upon. However, that would mean someone would have to do the work to code it and its effects. Although I'm sure I have plenty of "great ideas
myself on how to improve some of the terrain features of the game, I'm way too swamped (no pun intended) in my own personal life with my own business to have time to contribute to the effort myself.
Maybe some day...