Flash Flooding Follows Forest Fires
Arizona Governor Jan Brewer surprised few attendees at the Western Governors’ Association meeting last week when she acknowledged that one of her biggest fears as she began running the state two years ago was the possibility of a devastating wildfire. Her fears were realized this year as Arizona set a record for acres burned by wildfires. More than 800 blazes have sparked around the state leaving nearly one million acres—one percent of Arizona’s total land mass—burned. Where green once thrived, only dead trees and denuded ground cover remained—a prime setup for that ‘perfect storm’ when monsoon rains arrived.
Using ten wildfires-to-date on the 1.78 million acres of the Coronado National Forest as an example, eight of these blazes had soil charring characterized by Burned Area Emergency Response investigators as low-to-moderate in severity. The other two (the Monument and Murphy fires) suffered greater burn severity and merited most of the concern in their vulnerable upper watersheds.
The Monument Fire wiped out large swaths of the Huachuca Mountains before red-flag wind conditions pushed it into homes and businesses near Sierra Vista, destroying over 60 structures.
Of the soil burn severity involved here, nearly half the 32,000 acres were rated moderate-to-high. “If a high-intensity, long-duration monsoon storm occurs this year, erosion hazard analysis indicates there would be a significant sediment increase compared to pre-fire conditions,” predicted Forest Service spokesman Bob Ramirez.
Much the same prediction came following the Wallow Fire in Eastern Arizona—at more than 538,000 acres or 840 square miles, the largest in state record—fed by winds that consumed as much as 80,000 acres in a day and in the process, emptied entire hillsides of vegetation that would ordinarily prevent debris flows. Meteorologists and forestry folk alike agreed: “The biggest concern after fire is flooding ... a tsunami-like concrete wall racing downhill that can carry trees, boulders, cars, homes, and anything else in its path.”
“Mother Nature is Mother Nature and we can’t necessarily predict when and where it’s going to happen in these isolated areas,” admitted Deputy Sheriff Rod Rothrock. “If you can’t get your 4-wheel drive out through the wash, I can’t get mine in, so if you think you should leave—do so or you might be stranded for awhile.”
As soon as fire containment was announced and hot spots had cooled, the Natural Resources Conservation Service and Emergency Management Services personnel got to work. “We’re transitioning from Response Mode to Recovery Mode with one foot still in the response phase in case of new lightning-caused fires,” said EMS Coordinator Mike Evans. "We’ve got a very short window to ensure rainwater moves smoothly downhill and stays inside the washes. We know it’s going to rain heavily over the next couple of months and there’s going to be a lot of flooding, some of it very serious in the high risk areas populated areas off the forest itself.
“The state has given us 20,000 bags for sand, a neighboring county loaned us their sandbagging machine, and inmates from a nearby prison are filling those bags to be used to deflect water around residential structures rather than coming through the buildings.”
District Conservationist Gerry Gonzalez says that where Forest Service Burned Area Responders stop at their boundary lines, his group picks up working with private landowners. “We don’t put out fires, we work with the recovery and rehabilitation of land and resources, erosion, sediment, vegetation ... and we’ll have some radical hydrology coming up in these canyons,” he predicts.
Apple orchard/guest ranch owner Tom Beatty took a severe hit when Arizona flames raced down his property adjacent to the Miller Peak Wilderness Area, wiping out hundreds of his 1,300 apple trees. He’s now keeping a very watchful eye on the skies for heavy rainfall.
In New Mexico, the same wait is on for another large apple orchard owned by the Cochiti Pueblo tribe. “We expect rains in a severely damaged canyon that extends six miles and drains 20,000 acres to send a massive wall of ash, soil, and debris down the canyon and we’re working with the tribe to get things stabilized as fast as possible,” reported State Land Commissioner Ray Powell.
Weather prognosticators warn that flash flooding conditions could last through mid-September.
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