Measuring Moisture in Vegetation Helps Combat Wildfires

SCE partners with LA County Fire Department to start a program focused on protecting fire-prone communities.
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Stories : Safety

Measuring Moisture in Vegetation Helps Combat Wildfires

SCE partners with LA County Fire Department to start a program focused on protecting fire-prone communities.
Photo Credit: Maria Hedrick and LACoFD Forestry Division
Video Credit: Dean McDonnell and Roberto Lazarte

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As Tamara Hanna and her team hike up a trail near the San Gabriel Mountains, they methodically clip and collect new growth sprouting on the ends of branches, shrubs and other vegetation and place them in specially designed plastic containers as quickly as possible. The samples will be measured for moisture content to help combat California’s wildfires.

Hanna is a vegetation management coordinator with the Los Angeles County Fire Department’s Forestry Division and is continuing a decades-long process to help fight fires in Southern California.

“It’s really important to collect between 30 to 50 grams of live fuel samples because overcrowding the container can affect the air circulation and we’re trying to measure the amount of moisture in the plant itself,” she said. “As soon as you clip the plant it starts losing moisture very quickly through the atmosphere, which is why we seal the container immediately.”

Dan Sanchez, LA County Fire Department’s forestry technician, places new growth in a container.
Dan Sanchez, LA County Fire Department’s forestry technician, places new growth in a container.

SCE fire scientist Tom Rolinski recently joined Hanna to start the utility’s first live fuel moisture program. Rolinski is learning the process so the company can continue to expand its 2019 Wildfire Mitigation Plan to protect the public from wildfires.

“It’s best to learn from a team who has the knowledge, experience and the same dedication to protect communities from wildfires,” said Rolinski.

The data collected from live brush plays a critical role in determining how receptive the brush is to a fire starting in high fire risk areas. The live fuel sampling methodology that LA County Fire follows was created by the U.S. Forest Service.  

Tom Rolinski, SCE fire scientist, and Tamara Hanna with the LA County Fire Department examine vegetation from the field.
Tom Rolinski, SCE fire scientist, and Tamara Hanna with the LA County Fire Department examine vegetation from the field.

“We would like to fill in some of the gaps in the data that exists in our region. The more data we have will help us make improvements to our modeling of live fuel moisture in areas at risk for wildfires,” Rolinski said. “The better we understand conditions in the field, the smarter our response will be at preventing a small spark from growing into a large wildfire.”  

Once all the vegetation is collected, it’s taken back to LA County Fire’s Pacoima facility where the scientific work begins. All live plant samples remain in a container and are weighed to determine the moisture amount. Even the condensation that accumulates on the walls of the container is counted as well.

A vegetation sample (left) just removed from the oven and a new sample (right) just arrived to be tested.
A vegetation sample (left) just removed from the oven and a new sample (right) just arrived to be tested.

The next step is placing the plant samples in an oven at about 200 degrees for up to 20 hours. Hanna and her team are then able to determine the actual moisture content of each plant sample.

“All of the data collected is used as a predictive tool in fire modeling and allows LA County Fire Department’s incident commanders to make informed decisions that includes assessing the need for augmented staffing levels while preparing to fight wildfires,” Hanna said.