A powerful flash flood swept through Arizona's Grand Canyon on August 29, sending muddy water, huge boulders and debris through Bright Angel Canyon and the Colorado River. About 15 people may still be missing or unaccounted for, while authorities evacuated 62 hikers and campers from the affected areas, according to the National Park Service and reports cited by the Times of India.The Grand Canyon flood comes days after a catastrophic flood disaster struck the Nepal-China border, where thousands of people remain missing. The two disasters have highlighted the sudden danger that flash floods can create in mountainous regions, although the Arizona flood came from intense rainfall rather than the glacier-related disaster reported in the Himalayas.Grand Canyon flood sweeps through Bright Angel CanyonThe flood struck the Bright Angel Canyon and Phantom Ranch area at around 2.30 pm on August 29. Heavy rain over the Kaibab Plateau sent water rushing down the steep terrain and into Bright Angel Creek.The water quickly gathered mud, rocks and other debris as it moved through the canyon. The torrent eventually carried debris into the Colorado River and dramatically changed parts of the creek.The National Park Service initially said more than 20 people could be missing or unaccounted for. Officials later revised the working figure to about 15 people as they continued efforts to identify and locate visitors who had been in the area.— foxweather (@foxweather) 62 people evacuated from Grand CanyonRescue teams evacuated 62 hikers and campers from Phantom Ranch and areas around the lower North Kaibab Trail. Helicopters helped move people out as flood damage cut off parts of the canyon.The flood also destroyed nearly all footbridges crossing Bright Angel Creek, making several routes inaccessible. Water widened parts of the creek bed and created what appeared to be a new rapid.The National Park Service has asked people to share information about hikers and backpackers who travelled through the Bright Angel Creek corridor on August 29. Officials have also asked people with reservations at affected campsites to help them establish who remains unaccounted for.Phantom Ranch, Bright Angel Campground and the North Kaibab Trail remain closed because of the damage and continuing weather threat.Flood damages Grand Canyon water supplyThe flood caused another major problem by damaging the Grand Canyon's only water pipeline. The damage forced park authorities to restrict overnight hotel stays from August 31 and ask residents to conserve water.The pipeline already forms part of a $208 million infrastructure project aimed at improving the park's water system. The sudden flood has now added another challenge for authorities managing the affected infrastructure.The storm produced roughly 0.5 to 1 inch of rain over a short period. Because steep canyon walls quickly channel rainfall downhill, even a relatively small amount of rain can produce a powerful flash flood.More storms could bring fresh floodingThe immediate danger has not ended. Weather forecasts point to more thunderstorms in the region, raising the possibility of additional flash floods, debris flows and rockfalls.Park officials have therefore kept several affected areas closed while rescue and damage-assessment operations continue. The National Park Service is also working with Arizona authorities to account for people who may have been in the flood-hit corridor.The Grand Canyon disaster follows the much larger flood emergency along the Nepal-China border. Reuters reported that the Himalayan disaster had left nearly 800 people confirmed dead and more than 3,000 missing across Nepal and China by August 30. That disaster began after a glacier collapse triggered a massive flow of rock, ice and water into a Himalayan river system.The Grand Canyon event had a different trigger, but both incidents show how quickly water can become dangerous in steep mountain terrain. In Arizona, authorities now face the task of locating missing visitors, repairing damaged infrastructure and keeping hikers away from areas that could see another sudden surge.