Canyon flash floods are extremely freaky. A storm can be a half mile away, but the canyons can route the water to other areas. When I worked in the mountains out west (US) I actually saw flood waters come out of a canyon that happened so fast that had a few people been 5 seconds faster, they would have been hit with a river that simply appeared out of a side canyon. They were walking and the river simply poured out in front of us.
Another rain storm (which was to the northwest of us, caused another flood to come down the main canyon we were in. There were campers cooking that literally didn't have time to grab their stuff before the water sweep the fire from under their pots. They heard a roar, looked up to see a literal wall of water coming and ran to get out of its path. Canyon floods are scary stuff.

