A flash flood generated by a thunderstorm hit Zion National Park Tuesday afternoon, closing the main road, damaging a few camping tents, uprooting at least one large tree and disrupting electrical power for four hours.

"As of 10 p.m., there were no reports of injury or missing visitors, though a few tents and personal belongings were damaged in the debris flow from the side canyon," said park spokesman Denny Davies.The National Weather Service's new flash flood warning system, which began issuing alerts on Monday, had listed the possibility of flooding in the area as high. Park officials thought the Virgin River did not flood within Zion, but a sharp rise was recorded downstream near Hurricane, Washington County.

"It rose 3 feet in 15 minutes," said William J. Alder, meteorologist in charge of the National Weather Service regional office on North Temple.

At Hurricane, the storm dumped only 0.3 of an inch, but the river was swollen from the thunderstorms upstream. A river gauge showed that the surge hit the Hurricane portion of the river between 8:45 p.m. and 9 p.m., four hours after the Watchman Campground flooded inside the park.

The storm delivered lightning, strong winds and heavy rain, as well as pea-size hail. Three loops of the Watchman Campground were hit with runoff from a side canyon, which left 6 inches of mud, gravel and debris.

"After the storm passed, some campers voluntarily left the area while most others moved to the many other parts of the campground that were unaffected by the runoff," he said.

Debris swept across the Zion-Mount Carmel Highway, which connects the park with U.S. 89, cutting that artery for about four hours. By 9 p.m. emergency crews had cleared the debris and reopened the road.

Davies urged hikers to consult the National Weather Service spot forecasts of flash flood potential, which are posted in the park's visitor center, before embarking on any trips through narrow canyons.

"Everything is open at this point," park employee Janis Kali said Wednesday morning.