This RAPID project focuses on production and delivery of dry ravel, a characteristic and immediate post-fire response on steep slopes in the western USA. Dry ravel arises from a dry-season transport process whereby gravel sediment moving down hillslopes by gravity becomes trapped by vegetation. This material provides a significant sediment source into river channels after wildfire in chaparral environments. The investigators will quantify the volume of dry ravel sediment deposited along channel margins as a result of the Springs Fire that burned Big Sycamore Canyon in southern California during May 2013. Terrestrial laser scanning before and after the rainy season (which typically begins around October 1) will capture initial changes in landscape topography. These data will be augmented by field surveys. Data collected during the first post-fire year are important for developing models of the dynamics of dry ravel. The investigators have geomorphic data spanning over 25 years for Big Sycamore Canyon and two comparable basins nearby with different fire histories--a tributary to north fork Matilija Creek that burned completely during the July 1985 Wheeler Fire-- and a tributary to Malibu Creek that has remained unburned. Comparing dry ravel processes at these three sites will enable a direct comparison of both short- and long-term sediment dynamics following wildfire in chaparral environments.
Developing a predictive understanding of both short- and long-term effects of wildfire is critical, especially in an era of changing climate that has increased frequencies and magnitudes of wildfires. Yet, accurately predicting post-fire effects remains elusive, and physically-based models of post-fire runoff and erosion are still being developed. The proposed project will integrate research and education by involving undergraduate students from California State University, Channel Islands (CSUCI). These students will pursue their capstone undergraduate coursework while assisting the PIs with field data collection and analysis. Two of these students are participants of the Hispanic-Serving Institutes ACCESO (Achieving a Cooperative College Education Through STEM Opportunities) Research Assistant Program on the CSUCI campus. These students will receive valuable research experiences including training in use of cutting-edge technologies.
In May 2013, the Springs Fire burned Big Sycamore Canyon, CA. The NSF Rapid project goal was to study the sort and long-term effects of the fire on sediment dynamics (pre and post rain) to improve prediction and planning for future wildfires. The project focused on production and delivery of dry ravel, a characteristic and immediate post-fire response on steep slopes in the western USA. Dry ravel is a dry season erosion process whereby gravel sediment moving down hillslopes by gravity becomes trapped by vegetation. Dry ravel therefore provides a significant sediment source into river channels after wildfire in chaparral environments, which may result in debris flows and flooding. We collected baseline data that documented dry ravel processes immediately after the May 2013 Springs Wildfire prior to the onset of California’s rainy season in order to document geomorphic responses to storms during the first winter storm season following the fire. We compared these short-term responses to responses in nearby chaparral fluvial systems where wildfires occurred decades ago, which will allow for modeling of sediment dynamics after future wildfires and storms. We conducted two campaigns of Terrestrial LiDAR Scanning (TLS) and field data collection documenting dry ravel deposits and channel morphology post-wildfire, prior to winter storms, and post-storm. In order to investigate long-term sediment dynamics, we conducted field surveys at the same time in two nearby chaparral fluvial systems, where fire occurred 20-30 years ago, respectively. One small storm occurred on Feb 28-March 2, 2014 and generated only a small flow in Big Sycamore Canyon, yet transformation of channel morphology occurred. Concurrently, we collected field data from two nearby chaparral fluvial systems before and after the same storm. In these study sites burned 20-30 years ago, no significant changes were observed during the same small storm that greatly modified the recently burned Big Sycamore Canyon. These results indicate the magnitude of the channel response induced by fire. They also suggest that 20-30 years is sufficient time for geomorphic recovery to occur after fire in the chaparral environment. The project provided training in geomorphic field methods (surveying, measurement of dry ravel landforms, and sediment sampling) for undergraduate students and one high school student. In addition, undergraduate students were exposed to scientific data collection during our Terrestrial LiDAR campaigns. Undergraduate students had an opportunity to transfer their class-room knowledge to practical experience needed for future employment related to earth sciences. Four California State University Channel Islands students in the Environmental Science and Resource Management Program participated in the research as part of their Senior Capstone Projects: 1) Understanding Wildfire Effects: A GIS Approach in Modeling Sediment Mobilization 2) Evaluating the Universal Soil Loss Equation in Steep Slope Chaparral Environments Following Wildfire 3) Stream Flow Dynamics Following Wildfire 4) Long–Term and Short-Term Effects of Wildfire on Streambar Structure Processes In addition, these students were invited to present their poster "Effects of Wildfire in Chaparral Environments" to the CSU Channel Islands President's Circle and the CSU Chancellor’s Office. Resulting publications & Presentations: a) Two conference abstracts presented: 1) Geological Society of America, GSA Oct 2013; 2) American Association of Geographers, AAG April 2014; b) Two abstracts submitted for presentation at Fall American Geophysical Union, AGU 2014); c) One manuscript in preparation underway for submission to Geomorphology. This project also strengthened partnerships that will be important in addressing future wildfires and their environmental impact. Partners include: National Parks Service, Ventura County Watershed Protection District, and the National Weather Service. This was a collaborative research project with University of California Santa Barbara and University of Colorado Denver.
