A 2018 Association of Environmental & Engineering Geologists seminar titled Debris Flows: Understanding the Hazard, gave insight into the mechanisms of debris flows in burn areas. The intense heat from the fire reduces the infiltration of water into the soil in the upper 2 to 4 inches. This phenomenon coupled with the lack of vegetation and abundant small debris (ash and branches) increases the risk of a debris flow in burn areas. The increase in material can help boulder transport as well, leading to rockfall hazards where none previously existed.
Geocon worked with the County of Riverside under an on-call contract to evaluate areas adjacent to development with respect to rockfall hazard. The final report identified areas along Clinton Keith Road and within the Calle Del Oso Oro neighborhood that require further study.
County of Riverside Transportation Department
Paul Therialt, CEG