Burned, denuded hillside in the CZU Lightning Complex

The USGS landslide team monitors and continues to update the hazard map models based on data collected in burn areas. This information improves future models and provides better hazard assessments used by officials for emergency response and decision making. Many of the steep hillsides burned and denuded in California fires repel water rather than soak it in. This condition, called hydrophobic soil and caused by the fire’s hot temperatures, causes water to flow over land instead of soaking in, picking up surface debris along the way with potentially devastating force once it reaches people, communities or property.

The CZU Lightning Complex in the Santa Cruz Mountains of San Mateo County and Santa Cruz County experienced a massive wildfire in August-September 2020. Photo shows rilling and a shallow landslide within the CZU Lightning Complex near Eagle Rock, California. Soil about 3 centimeters below the surface was almost completely dry after the rain storm, highlighting soil water repellancy.