Who kept flooding the streets?

Indeed.

No, there had been a thunder storm one night near the end, giving the streets that watery sheen that in movies has for some reason always signified urban noir. For most people there's something about a wet (damp but not flooded) city street that conjures up feelings of exposure, loneliness, alienation in an urban setting, through which the central character walks alone and at the mercy of the elements. Maybe it's one of these primordial feelings buried deep within human beings that causes us to instinctively react to such sights in a predictable way. So many dark films set at night in cities utilize this device that by now audiences are primed to react to it in the appropriate manner, though no one ever thinks about it or even realizes it.

In fact, my crack about that fictitious company was swiped from an old Mad magazine spoof of the 60s TV series The Fugitive. At the end, Richard Kimble (called "Richard Thimble" in the spoof) is seen walking off into a darkened, glistening city street, slightly hunched over, hands in pockets, as the narrator talks about his unceasing efforts to find the one-armed man, while in the foreground is a guy holding a hose, spraying water on the pavement and wearing a white uniform with "The Making Streets Look Like They Just Rained Company" emblazoned on the back.