Stephen Caruana
The Cocos Fire one month after the 2014 blaze. The May outbreak …
Know your environment
The best way to predict erosion is to look at the native environment. The number, size, and location of vegetation, slope and soil characteristics, and fire intensity influence the severity of erosion.
Inside the fire, the naturally produced oils, resins, and fats stored in vegetation and leaf litter are vaporized and released into the atmosphere and soil. As the vapors cool, they condense into the lower, cooler soil below the surface, creating a hydrophobic, or water-repellent, layer that increases the rate of runoff and lessens infiltration, making it difficult for seeds to germinate and for the roots of surviving plants to obtain moisture.
As water saturates the surface, the soil reaches a tipping point that, combined with a lack of vegetation, causes it to slump, or slide, downhill. One acre of soil a foot deep produces about 2,000 tons of material. That can cause considerable damage in a landslide.
Also, previously deposited debris can remobilize, become unstable, and contribute to a secondary avalanche. In dry climates, or where it takes significant time for soil to re-establish, the landslide risk can last five years after a fire.
Averting landslides or other erosion-based events requires site-specific control plans that consider regional population, flora, fauna, and geology.
Next Page: Once the fire’s out