Floods follow fires: Leaders prepare for post-Bighorn Fire monsoon

Flooding concerns after Bighorn Fire

ORO VALLEY, Ariz. (KOLD News 13) - All eyes have been on the Bighorn Fire since it sparked on June 5.

But now, city and county leaders are preparing for what comes next — monsoon and flooding.

“This isn’t our first rodeo with a fire on the mountain,” said Oro Valley’s public works director and town engineer, Paul Keesler. “We’ve been following this since Day 1.”

Right now the town of Oro Valley is reviewing the effects that seasonal storms could create within the upstream watersheds due to the Bighorn Fire.

After flooding hit the town of Oro Valley in 2003 after the Aspen fire, Keesler said they’re trying to prepare for the rainfall by alerting residents.

“What that did is that taught us to be a lot more proactive on this so as soon as we started seeing the fire we were getting out the maps and do our analysis.”

A wildfire right before monsoon season is a big cause of concern. University of Arizona Research Scientist Ann Youberg said that’s due to the burned landscape turning soil into a slide.

“The fire consumes the vegetation so there’s no longer a plant canopy to intercept the rain fall,” said Youberg. “You actually have more water hitting the soil and because there’s more water it runs off faster, there’s nothing to stop it, and the soil is easily eroded.”

She specializes in post-wildfire debris flow, something that happened after the Aspen fire. And although it’s too early to tell what the Bighorn Fire’s flow will look like, it’s burning in similar areas, which could mean history repeating itself.

“Do we have evidence of past debris flows? And if we do have evidence of past debris flow it’s likely that watershed could have another debris flow,” said Youberg.

One of the main watersheds Oro Valley has its eye on is Canada del Oro that starts on Mt. Lemmon and makes its way down to Oro Valley. It’s why the town is alerting the homes around it.

“It’s likely that watershed could have another debris flow.” said Youberg. “What we don’t know what the likelihood of that debris flow is what the size, the magnitude, the volume of that debris flow might be, and we don’t know how far downstream it might travel.”

But Youberg and Keesler want to share the same message for everyone across the town and county.

“You should have flood insurance and if you don’t have it go out and get your flood insurance. Every rain storm can fall in a different part of the watershed and have a completely different response than what the different part of the watershed did.”

Because like wildfire, monsoon storms are unpredictable and it’s better to be safe than sorry.

"We should just be really aware and cognizant that it can happen anywhere. And this is a monsoon to be paying attention during," said Youberg.

What the town of Oro Valley’s Public Works Department is doing to prepare for post-wildfire floods:

  1. Coordinating with the Forest Service and Pima County Regional Flood Control District to assess flood and fire conditions
  2. Identifying watersheds affected by the fire and assessing impacts change the amount of runoff
  3. Identifying Town infrastructure that needs to be cleaned out and assessing how the impacts change the amount of runoff
  4. Identifying and implementing possible flooding protection measures
  5. Determining vulnerable properties and contacting those property owners
  6. Coordinating with ADOT to ensure drainages underneath Oracle Road are cleaned out
  7. Reaching out to homeowners, businesses and homeowner associations in the affected areas

“All residents living below the areas impacted by the Bighorn Fire should look into purchasing flood insurance before monsoon arrives. If you are near a wash that doesn’t have a mapped floodplain, contact the town to see if your property might be affected by post-wildfire flooding to help you determine whether flood insurance is appropriate,” added Keesler. “The post-wildfire exception for flood insurance is important to understand.”

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