IMPACTS OF THE 2016 ERSKINE FIRE ON THE PHYSICAL PROPERTIES OF SOILS

Wildfires over the past few decades have been impacting an increasingly larger area of the southern Sierra Nevada. The effects of wildfires on landscapes, and soils in particular, can increase the frequency of debris flow events, which pose a greater risk to people, as the wildland-urban interface expands into the Sierra Nevada. Alterations in the physical properties of burned soils are one such effect that can catalyze slope failure and debris flow events, and previous studies reveal that the degree of a soil’s physical alteration resulting from wildfire has been linked to burn severity. In this study, the physical properties of soils with varying degrees of burn severity are explored within the Erskine fire perimeter. The Erskine fire ignited in June 2016 in the southern Sierra Nevada, burning 48,019 acres, resulting in soils of unburned (or very low), low, moderate, and high burn severities. Unburned (VLBS), low (LBS), moderate (MBS), and high (HBS) burn severity soil samples were collected within the Erskine fire perimeter, and the influence of burn severity on the physical properties of soil are explored using X-ray diffractometry (XRD) analysis, grain size analysis, liquid limit, plastic limit, total organic carbon content, and shear strength tests. Total organic carbon (TOC) content increased with increasing burn severity. HBS soil has the highest liquid limit, followed by LBS, MBS, and VLBS soils. Plastic limit increased with increasing burn severity. Analyses from XRD, grain size, and shear strength testing are being finalized. Results from this study will be used to help constrain the effects of burn severity on the physical properties of soils and to assess debris flow hazard models within burned areas of the Kern River watershed in the southern Sierra Nevada.