How is krakauer able to corroborate(strengthen or support with other evidence) the events in the detrital wash?

I believe there is a map that goes with this question. Were you provided with a link to the map, or is it in your textbook?

It is believed that Chris left the car (abandoned it) because of a flash flood. On Page 28, Krakauer describes it in this way;

"With the battery dead there was no way to get the Datsun running. If he hoped to get the car back to a paved road, McCandless had no choice but to walk out and notify the authorities of his predicament. If he went to the rangers, however, they would have some irksome questions for him: Why had he ignored posted regulations and driven down the wash in the first place? Was he aware that the vehicle's registration had expired two years before and had not been renewed? Did he know that his driver's license had also expired, and the vehicle was uninsured as well? Truthful responses to these queries were not likely to be well received by the rangers. McCandless could endeavor to explain that he answered to statutes of a higher order--that as a latter-day adherent of Henry David Thoreau, he took as gospel the essay on 'On the Duty of Civil Disobedience' and thus considered it his moral responsibility to flout the laws of the state. It was improbable, however, that deputies of the federal government would share his point of view. There would be thickets of red tape to negotiate and fines to pay. His parents would no doubt be contacted. But there was a way to avoid such aggravation: he could simply abandon the Datsun and resume his odyssey on foot. And that's what he decided to do."