The late summer flash flood season announced its official startlast weekend by wiping out Supai Campground along Havasu Creek in the Grand Canyon. A huge flood hit around 3 a.m. on Saturday, August 16th, sweeping through the campground, which is located several hundred yards above famous Havasu Falls.
Apparently the river began its rise gradually, and waters turned muddy brown, offering a modicum of warning as the rumbles got louder. In response to shouts of alarm, roughly 100 of the 200 campers in the canyon scrambled up a cliffy slope to high ground at the Havasupai cemetery, but an undetermined number ended up stranded on ledges and in trees. One party of 16 rafters who were moored where Havasu Creek meets the Colorado River, eight miles below the main falls, were also stranded after flood waters washed away their boats.Five rafts were later seen floating on the Colorado with life jackets and personal gear still aboard.
Eleven campers who were thought to be missing have been accounted for. At least 350 campers and tribal members were evacuated from Havasu Canyon by helicopter on Sunday and Monday. Access to Havasu Canyon is now prohibited.
Supai Village, located two miles upstream of the campground, and home to over 400 members of the Havasupai tribe, was not inundated. However, the flood wiped out trail access to this remote village, along with the tourism on which the tribe depends. A similar flood occurred 10 years ago and resulted in large economic losses. Nearly 20,000 people visit Supai each year, mostly to view Navajo, Mooney and Havasu Falls, or camp along the creek with its pale "travertine" blue water, courtesy of dissolved calcium carbonate. Havasu'Baaja is the tribe's native name for itself. It means 'people of the blue-green waters.'
This flood was originally thought to be caused by a collapse of the earthen Redlands Dam 40 miles upstream. It was later determined that the flood resulted from thunderstorms on Friday and Saturday that dumped 3 to 6 inches of rain some 20 to 40 miles upstream on Cataract Creek, which feeds into Supai Canyon. The resulting flood blew out the Redlands reservoir, which added force to the natural event.
Flash Flood 101
Flash floods like this (and worse) are common in late summer and early fall throughout the American Southwest, fueled by intense thunderstorm activity that cranks up when seasonal storm tracks shift to 'monsoon' mode, bringing moist air northward out of the Gulfs of Mexico and California. Devastating canyon and riverbed floods can occur anywhere, but true wall-of-water floods are extremely rare in well-vegetated regions. In redrock country, most narrow canyons flood at least once or twice each summer, and the season can run into October.
There was a time when I was obsessed about videoing flash floods, which are common around my Torrey, Utah home. I witnessed quite a few at very close range, and from those impressive experiences I learned several important flash flood safety lessons:
--Know the weather forecast where you'll be hiking, but realize that thunderstorms can be isolated events. If thunderstorms are prowling, stay out of deep drainages.
--Know the layout of any canyon you'll be hiking in - how long it is, which direction it runs, and what and where the major upstream tributaries are.
--Always have a backup activity planned when you go canyoneering or hiking in flash flood country; That way you won't stubbornly proceed if the forecast is sketchy.
--Floods can originate dozens of miles away and surprise hikers who are traveling in bluebird conditions - but most desert canyons aren't that long, and it's usually obvious that the situation's bad.
--It takes a serious downpour - somewhere - to create a dangerous flash flood; Your average storm squall isn't enough.
--Flash floods can take a surprisingly long time to develop and reach your location, and the delay is unpredictable. I waited four hours for one flood to travel a mere 10 miles. I've also seen a smaller flood travel that same streambed in 45 minutes. But a flood that builds slowly can still arrive as a raging wall of mud and logs traveling 30 mph. I'm not sure what the mechanism is here, but be very cautious moving into a canyon again after rain ceases. It's easy to assume the coast is clear and then get nailed.
--Flash floods can also come in waves as a thunderstorm travels across upper finger tributaries of a canyon. Don't assume the flood that just subsided will be the only one.
--In a steep, winding canyon, you may only have 5-15 seconds of warning, depending on how far upstream you can see. Only the most attentive, athletic - and lucky- hikers could pull off a streambed escape that quickly - assuming they're not walled in.
--If you get hit by a REAL flash flood, you will probably die. None of the large slot canyon floods I've seen were remotely survivable, due to the power of silty water and the tumbling log piles that usually form the leading edge of a flood wall. Consequently, DO NOT enter any confined canyon if thunderstorms are underway.
--If you're lucky, you may get a warning. Flash floods are usually (but not always) preceded by water turning a murky brown or red, as the initial silt load washes into the stream. It can be very difficult to hear a flash flood coming if you're alongside a canyon-bottom stream. The water echo off walls will obscure its approach. If winds are blowing downstream, you may be able to smell a flash flood coming. All the floods I've witnessed had a strong smell like rotten mushrooms and burnt gunpowder. But don't assume you'll get any notice.
--Most flash floods subside quickly, within a half hour to four hours. Do not attempt to cross flood waters, assuming you'll be trapped long-term.
--Never attempt to view a flash flood by traveling upcanyon - the time lag is far too unpredictable. However, if you can safely travel overland to a good viewing point well above the streambed, enjoy: It's a learning experience you'll never forget. Just make sure you're high enough above the drainage, because flash floods can arrive far larger, higher, and faster than you expect.