In my setting, an apocalyptic supernatural event made the earth into a gridded globe of "squares" (more like columns) that are roughly 2x2 miles at sea level, getting larger going up and smaller going down (so there are no "gaps" between squares at higher altitudes). Each of these squares is subject to a different supernatural gimmick, and the first one that my protagonists start in is one that will, for obvious reasons, come to be known as "Fishtank".
It has invisible walls on all four sides of the square that don't let you pass through until you get a certain height above ground that I haven't decided on. This square is also subject to constant, unceasing rainfall at a rate of about an inch per hour. The idea with this square is that eventually, the entire thing will be flooded to the top of the invisible walls, with water constantly spilling off the sides of the invisible walls and eventually forming rivers.
The heroes' immediate concern, however, is getting out of this place before the flooding starts making the place a serious drowning hazard, because things are crazy all over the world, this is just the start of the heroes' problems, and nobody's coming to help them. The end goal story-wise is to have the heroes spend a week at most in this place, with the flooding making survival increasingly dangerous all the while, before they finally come up with a way to climb high enough to escape and then safely get down to the ground. As such, I need to get a good grasp of what exactly flooding an enclosed area with an inch per hour of rain would look like, and how quickly the flooding would actually happen, so I can adjust my numbers accordingly to make the flooding happen fast enough to be dangerous without happening so fast that the rain itself would be a serious danger even before the flooding happened.
Assuming this 2x2 mile square is in the middle of a flat suburban town, How long would it take before the sewage systems and other below-ground spaces are saturated, visible flooding begins, and the water level of this square starts rising?