WOO--HOO!! That water looks REAL. My dog would have a field day chasing trains. Squirrels, would breath a sigh of relief. LOL LOL
I would hate to keep those tracks clean! Water is real, you can see something drop into it early in the video. Very cool video!
Outdoor HO seems to be more popular in England than here in the US (although they use OO scale). That would be fun to do with a large backyard, but you just have to make sure that your plastic ties and roadbed aren't damaged by UV light. Some plastics become too brittle after exposure to the outdoors for long periods of time, but using PCB ties may alleviate the problem. As long as you can find a way to secure the track to the ground and prevent it from being overgrown by grass, a lot of G scale techniques probably work on HO too.
My layout sat out for about 7 years and it was fine. The rail naturally weathers to black and all you do it clean the rail heads. Switches you want to put covers over, otherwise it's actually pretty doable. Maintenance is required, yes. But look at that real water and real rock.
