Wildfires and floods may seem like opposite disasters. But in the American West, they are closely linked — and the destruction happening across hillsides and forests this summer could determine where floodwaters surge this winter.

Wildfires not only leave behind ash and scorched trees, they fundamentally rewire how the landscape handles water. When atmospheric rivers and winter storms arrive in the months ahead, the burn scars left behind this summer become elevated flood-risk zones for the next season. 

How fire alters the ground 

To understand why wildfires elevate flood risk, you have to look beneath the surface — literally.

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Burn scars create lasting vulnerability. Intense heat can create a water-repellent, or hydrophobic, layer in the soil, limiting how much rainfall can be absorbed into the ground.

Canopy interception is another mechanism. The loss of trees and vegetation removes the canopy that normally slows rainfall to the ground. As root systems decay, they also lose the ability to hold soil in place. Ash, rocks, and burned debris sit exposed on slopes, becoming highly mobile during rainfall.

A dangerous combination. Water that would normally be slowed, absorbed, and filtered is instead accelerating downhill, picking up ash, sediment, and debris as it goes. When heavy rain or melting snow reaches these burn scars, more water flows across the surface — leading to faster runoff that erodes the weakened landscape.

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The West’s winter water cycle 

Atmospheric rivers and the snowpack question. 

Atmospheric rivers are the primary driver of winter precipitation across the West Coast and Interior West. For recently burned areas, an atmospheric river can be a worst-case scenario — drenching vulnerable burn scars with intense and rapid rainfall that hydrophobic soils cannot absorb.

The same systems that bring coastal rain build the snowpack across western mountain ranges. But burned slopes accelerate melt without root systems to hold the soil in place. When a warm atmospheric river delivers rain directly onto existing snowpack, already vulnerable burn scars like the Aspen Acres fire in Colorado and the Cottonwood fire in Utah face their greatest test. 

The mountains in the crosshairs 

The Interior West has seen a historically dry season this year, with below-average snowpack leaving soil moisture levels low heading into fire season — conditions that allowed fires to spread faster and burn more intensely than in wetter years.

With little moisture in the soil and vegetation already stressed from drought, the landscape had few natural defenses against this season's fires. The Cottonwood fire in Utah burned over 97,000 acres and the Colorado fire burned over 99,000 acres of terrain. When precipitation arrives, the slopes are primed for flooding — debris and ash from destabilized soil will quickly mobilize on steep slopes, channeling debris flows into the canyons below.

Impacts to communities 

The fires burning across Colorado and Utah this season are damaging the terrain surrounding ski resorts, campgrounds, and mountain communities that depend on recreation and tourism. Eagle Point Ski Resort in Beaver County, Utah, has seen fire damage to surrounding terrain, leaving slopes scorched and destabilized. Aspen Acres campground in Colorado is among the recreation areas already affected by fire scarring.

For communities built around outdoor recreation, the damage from fire is only the beginning — a lingering flood threat follows close behind with every rain and snowfall. The flames may be gone by winter, but the landscape left behind can remain vulnerable long after the smoke clears.