basement question - possible trench?

I've been living at my townhouse 6 months. My basement is finished, so I can't see, from the basement itself, if there is a trench near the foundation walls. One thing I failed to notice until now is that my garage floor (which is a basement level, below grade, garage) seems to be intentionally designed so that it is several inches, or more, lower than the level of the basement itself. You could think of it either as the garage floor being lowered relative to the basement, or the basement being raised relative to the garage.
In addition to being lower than the level of the rest of the basement, the garage floor is also appears intentionally sloped downward (VERY obviously sloped downward...higher toward the rear and lower toward the front). If I look at the corner of the garage's rear wall which divides the garage from the basement, it appears that somebody intentionally left that corner of the drywall unfinished.
Call me crazy, but to me, it appears, from looking at this corner, that there might be a trench or gap on the side of the basement wall, and the drywall in that particular corner was intentionally left unfinished so that, if this trench exists, and got filled with the water, it would likely just run into the garage and eventually under the door and outside of the house. Granted, this setup (having water run through the garage to prevent a flood) is less than ideal, but it would beat the heck out of the water staying in the finished basement.
I'm not planning on ripping up the finished basement to find out for sure if there is a trench. I can only base what I'm saying on the fact that when I viewed the corner of the garage, and I peer through the dividing wall between the garage/basement it appears that there is a 2 inch gap between the basement's concrete floor and the foundation wall, and this appears to be some type of trench (albeit filled with debris that looks like pieces of concrete).
Is it likely that they designed my basement and garage this that way to prevent the basement itself from potentially getting flooded, or do you think I'm mistaken in believing this?
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