Wildfires in the West: Characterizing Drivers of Post-Disturbance Hydrologic and Sediment Response through Laboratory Analysis
Conference Proceeding
Overview
abstract
Wildfires are a perennial problem across the western U.S. and internationally. By increasing; watershed sedimentation rates to 25 times or more above non-wildfire base levels and raising; concentrations of dissolved organic matter (DOM), fires create a major challenge for; downstream water treatment plants. The overarching goal of this research effort is to test the; response of sediment and runoff responses of soils at a range of burn severities, rainfall; intensities, and terrain slopes. This paper will focus on the first phase of the project, exploring; issues related to building the laboratory rainfall and wildfire simulators, and will discuss issues; related to up-scaling of results to representative watershed scales to improve predictions of; post-fire suspended sediment in streams.; Here we explore best practices for capturing burn, rainfall, and terrain related processes in the; laboratory. The key experimental settings–burn temperature and duration, rainfall nozzle type; and intensity–were determined based on published precedents and local historical; observational data. Temperatures between 150 and 550°C, 30-minute burn duration, a FullJet®; nozzle, and a maximum rainfall intensity of 2.5 in/hr were selected. We present synthetic results; using a numerical model in order to anticipate how the soils will respond to the above settings to; inform the subsequent laboratory testing. We have collected a series of soil samples from a steep; mountain catchment with wildfire history: The Cache la Poudre (CLP) Basin near Fort Collins,; CO that will form the basis of the laboratory experimentation. Samples will be exposed to; burning and rainfall processes under combinations of burn temperature, rainfall intensity, and; terrain slope, with differences in runoff sedimentation and DOM exports analyzed across these; dimensions. A longer-term goal will be to apply up-scaling techniques of post-fire sedimentation; prediction to entire catchments, in an effort to red
