The woman who died at the base of the Grand Canyon from a flash flood in the Colorado River and the 4 with her who were injured were like Sitting ducks

In other words they didn't have a chance in this situation and anyone is lucky to have survived this where they were. Why?

Because likely cell phone service wasn't happening so no one could warn them because of their location and because they were just above the river in altitude when the flash flood came down the river it was lucky ANYONE survived this.

Because no one can see storms in the canyon so there was no way they would know to protect themselves and seek higher ground so that they all could survive uninjured or dead.

Because of the 26 year drought and the the non-porous condition of soil throughout the American west any water coming down out of the sky isn't going to go into the ground but going to wash off and create various kinds of havoc in Arizona, Nevada, New Mexico, and maybe California and Texas and Utah.

So, I wouldn't recommend in camping anywhere near dry washes or anywhere near where the Colorado River is especially anywhere it goes through the Grand Canyon unless you want to wind up like the people I mentioned above.