I'm writing a story that revolves around people surviving the aftermath of the world becoming a gridded globe of 2x2 mile (at sea level) areas that come to be called "squares". Every "square" is subject to a different supernatural gimmick, like sideways gravity, or complete nullification of sound, or mutating anyone who spends too long inside its borders. I initially envisioned this as something taking place years after the fact, where the heroes would be traveling across the country in search of something, going through all sorts of fantastic obstacles as they went. But I swiftly realized that the immediate aftermath of this event was far, far too interesting of a story to simply pass up. And it's swiftly becoming apparent that that's more of a problem than I realized. I've come up with tons of ideas for square gimmicks, and an awful lot of them would be way, way more interesting if they were introduced right after the supernatural event happened. For example: I have a square where the borders (normally entirely for show and fully permeable) are impassible below 100 feet off the ground, and it constantly rains until the entire place is eventually drowned in water days later. Or a square that doesn't let anyone escape while there are too many people alive within it, forcing the inhabitants into a brutal battle royale for the right to leave. If I introduce these years or even just months later, then everything that makes them interesting will have already happened. The former would just be a gargantuan fish tank overflowing with water and making rivers, and the latter would never be interesting again because there would never be more than one person over the limit within it ever again. I have lots of square ideas like that, where being in the square when the apocalypse starts is way, way more interesting than coming across the square a while later, and I feel a desire to tell all of these initial stories. But I can't, obviously. There just wouldn't be enough space or time to tell more than, like, three at most. So I find myself struggling with how to prioritize which ones I want to use, and determine which ones I can afford to throw away. Any tips?
You could interweave the current traversal with a flashback of a different POV encountering the zone at inception. Maybe only do it for the zones that really need it... or something like every third zone. The concept alone sounds like its a natural fit for a more serialized mould.
I use lots of "Tell, don't show" in places when I realize I just need to get the story moving faster.
None of those ideas have anything to do with a story arc. What's your story about? What are you wanting to say? Don't get bogged down in clever details.
I can't really answer your question because this is all world-building really, there's no plot explained. Which means I can't put your ideas into context.
I once cooked up a similar idea that I called Pitworld, only in mine the planets surface was heavily cratered with massive pits and a different ecology developed in each one. Yours sounds far more magical or magical/techno in conception, mine was more natural. Of course heavy flooding in one square will run off into surrounding ones, unless there's some kind of impenetrable magical barrier to stop it. I think you'd get a lot of bleedthrough into surrounding areas.
Focus on the story, but save all the interesting ideas you don't use for a companion book written in the future by a historian who is gathering all the stories from around the world.
Just looking at your dilemma, @Simon Price . I think you may have painted yourself into a corner, in a way, because you've set this up so nothing can ever change in these separate sections of your world. So, as others have pointed out, there is no story. Yet. I think we might need a bit more information. What is this 'supernatural' you mention, as being responsible for this? Is it a being of some sort? Or just a force? Why would 'supernatural' have divided up the world like this? What was its purpose?