Experts analyze burned soil in anticipation of Thomas Fire flooding

Mud and debris flow a large concern

Thomas fire flood concerns

OJAI, Calif. - The Thomas Fire may be nearing full containment, but the threat is far from over. 

Any significant rain will likely cause flooding and debris flows in and around the burn areas. 

Soil scientist Eric Nicita with the United States Forest Service combed through the burned soil in Matillija Canyon in Ojai on Sunday. 

Nicita is looking at how hot the soil burned during the Thomas Fire, then creating severity and debris flow maps. Those maps will explain just how much water, mud and debris will flow down the denuded hillsides during a storm. 

"Two of our biggest concerns are the increase in flooding and the debris flows," Nicita said."We know this is a really active channel now we've burned off 80 to 100 percent, we're pretty sure we are going to see this kind of deposit in a greater magnitude."

Those deposits could flood communities, roads and reservoirs below. 

The Matillija Reservoir is a good example of the potential impacts. It's already full of sediment and if a significant rain happens more ash and debris will likely cause it to overflow and head towards homes and infrastructure.

Nicitita says the site at Matillija Canyon is a good indicator of what other watersheds in Carpinteria, Montecito and Santa Barbara will do during a storm. 

"Now that all of the field testing is done, all of that data will be handed over to local counties and water agencies so they can create an action plan once the rain comes," Nicita said. 

Officials stress the most important thing is to heed any evacuation warnings.


The assessments for the Thomas Fire are being organized into four geographical areas:

  • Ojai – Burn severity and debris flow assessments are completed and have been shared with local government leaders who will assess and respond to risks to the local community. BAER-recommended treatments to improve the stability or reduce erosion from forest roads and trails have been initiated. 
  • Santa Paula – The Forest Service BAER team will provide burn severity mapping to local, state and other federal agencies for use in hazard and risk-mitigation planning.
  • Santa Barbara – The majority of National Forest System lands is north of the urban interface and is very steep. The Forest Service will partner with local Office of Emergency Services and the state to complete this assessment.  The primary work will occur in the Wildland Urban Interface to provide for the life, safety and flood preparedness of the community and mitigation to any fire-related resource damage. 
  • Wilderness and Backcountry – This area will be assessed as conditions allow, focusing on roads, trails and other affected resources. Recommend treatments will be implemented before any seasonal precipitation can cause damage. 
  • Not every wildfire affects the landscape in the same way, so areas that may not have been flood- or slide-prone previously may now be at risk. County-based emergency service agencies are reviewing assessment reports from the BAER and WERT teams and working on emergency preparation plans for affected communities. After a wildfire, flood risk is usually highest until vegetation returns, which can take up to five years.


Flood preparation information is available at:


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