Or in this case when you can't even tell where the street IS anymore.
Several years ago, I lived near one of the Bay Area's hidden pockets of ruralitude during an "El Nino" winter. That's a large-scale oceanic-atmospheric phenomenon whose local consequence is Old Testament rainfall.
Nearby is a place where some steep wild hills met the backwaters of a reservoir via an easily clogged culvert. Between hillside and lake there runs about a lane and a half of little old blacktop country road that population trends have turned into a minor but busy back-door commute route. Typically of little old country roads never meant for heavy traffic, there's a dip in the road right where the water wants to go.
One rainy night I was headed into town and noticed that there were deputies with the cop lights going on either side of a small new lake where the road used to be. It was easy to judge the depth of the lake because of the cars in it -- in the middle, about grille deep on a regular pbuttenger job.
Back then I had a raised Jeep wagon and a modest collection of off-roading goodies in the back, and besides the depth cues I could see that the water wasn't flowing or rising, so I waddled out there in four-low to push and tow those who wanted it. This gave me an interesting opportunity to observe different strategies for a water crossing.
A surprising number of people seem to think the problem is either loss of traction or some statistical function of transit time, and thus you should do it as fast as possible. A minivan driver I towed out told this to me pretty explicitly -- he thought the way to do it was to go really fast. What it bought him, and some of the others, was an intake and quite possibly an engine full of muddy water.
A more prudent approach would of course be to go just fast enough to set up a bow wave that travels with you. This tactic was used by most of the people who made it through, though the traffic jam, presence of cops, and stalled cars made most people turn back or take Plan B at a nearby intersection.
The only two cars I saw succeed with the speedboat approach were a high-riding pickup truck and a a Subaru, which is thoughtfully designed in certain ways that let it get through some surprising amounts of ick for a small sedan.
A couple of kids in a ratty 80s BMW dodged a bullet, financially. Their problem was an exhaust system that filled with water after the car quit (the intake was high and dry). They had a subsidiary problem with battery terminals supporting some kind of non carbon based alien ecosystem, and couldn't crank after stalling out. A bit of work with a battery-terminal brush fixed that, and a great deal of cranking caused enough water to belch out of the exhaust pipe to get the engine restarted.
By then it was pushing ten o'clock. The minivan guy told the tow truck driver where to take the thing when they got to it amid the collection of saturated vehicles on the high ground. He lived on my way home, so I gave him a ride and explained the range of what might have happened, and what to do about it in the various scenarios, and the various strategies and tactics for avoiding a similar mess the next time.
Although fortunately nobody drove into any cars or people or the reservoir, I think several overhauls were sold that night, not to mention a fair amount of dry cleaning as people in business attire ended their day wading out of their car.
--Joe "If in doubt, turn around, go uphill, and find another route" Chew
