Around here, well more like Tucson, there are such things as run-off streets or flood streets(much less of those now), these were actually built to channel water rather than dump it. And this would be combined and dump into 'washes' most often. Like all river systems, the washes tend to combine too. Anything solid could push up against a large bush or rock and get buried under a type of sticky (yet slick) red mud we have.
An uncertain number of people died back in the day, thinking their floating VW was safe to cross 4in of fast moving 'red' water. (read that as slick) If 'this one' crossing didn't work out, it would just float yes? Trouble is, 4in was enough to drag it into deeper faster moving water, and of course you didn't stay upright in it.
The process: roll many times, mash windows, fill up with water, get trapped by bush or rock, sink, 'turbolate' into muck, disappear for a week or more with-out a trace.