How wildfires like the Molino 3 Fire can impact floodplains

TUCSON, Ariz. (13 News) - This summer’s extreme heat and lack of moisture are perfect conditions for wildfires to flourish.

According to experts, wildfires burning in high mountain regions like the Catalinas are changing floodplains in lower elevations.

This is why flood officials will keep a close eye on the aftermath of the Molino 3 Fire and any future blazes.

Fires like the Molina 3 fire burning on Mount Lemmon right now have a bigger impact on floodplains in Pima County than one might think.

Brian Jones, the Deputy Director and Flood Administrator with Pima County Regional Flood Control District said when vegetation and shrubs burn because of wildfires, it allows more water from rainfall to flow down the mountain, causing more flooding in different areas.

“What we like to say is everyone is in a floodplain,” Jones said.

Michael Bishop, the Risk Analysis Chief for FEMA Region 9, said different weather patterns can impact floodplains in southern Arizona.

“We have seen some of the anticipated expansion in some cases and contractions of floodplains in some places,” Bishop said.

Jones believes the Big Horn Fire back in 2020 caused changes to floodplains. This is why keeping a close eye on wildfires like the Molino 3 Fire is vital.

“Vegetation-type land cover has a significant impact on flooding and how much water runs off the land’s surface,” Jones said. “Vegetation intercepts rainfall, it absorbs rainfall with through uptake of water through plants.”

It’s not just wildfires. Jones and Bishop agree both non and active monsoons, droughts and any other weather event can also contribute to the problem.

“There are always bigger rainfall events, always changes in the watershed, whether it fires, like the big-horn fire, whether it’s development in the floodplains,” Jones said.

Jones and Bishop said since conditions in Tucson are always changing it makes floodplains more difficult to map.

“That really is just dependent on conditions, on ground conditions and climatic pattern,” Bishop said. “If you can imagine there was an increase in monsoonal events. It might push more water down through any individual flooding source.”

Pima County officials are working very closely with FEMA to re-map the floodplains in the county. They are in the middle of the process and hope to have the new floodplain officially mapped out in about two years.

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