I mentioned some books to our group about history of Belfast which include nice old photos which it would be fairly easy to compare to current photos. I couldn't remember the titles at the time though. These are: Once upon the Lagan by May Blair and the Rivers of Belfast by Des O'Reilly
While searching the internet to remind myself of these names I also came across this piece:
Belfast’s Hidden Rivers – Hidden Hydrology https://www.hiddenhydrology.org/belfasts-hidden-rivers/