What happens when Chris drives the Datsun into the Lake Mead National recreation area

Chris was forced to abandon the car after the area experienced flash flooding. The entire campsite was washed out.

McCandless was camped at the edge of the wash, a couple of feet higher than
the main channel, so when the bore of brown water came rushing down from the
high country, he had just enough time to gather his tent and belongings and save
them from being swept away. There was nowhere to move the car, however, as
the only route of egress was now a foaming, full-blown river. As it turned out,
the flash flood didn’t have enough power to carry away the vehicle or even to do
any lasting damage. But it did get the engine wet, so wet that when McCandless
tried to start the car soon thereafter, the engine wouldn’t catch, and in his
impatience he drained the battery.