DWR: Understanding the effects of wildfire on fish populations and stream geomorphology in Twitchell Canyon
January 2013 - September 2018
- Utah Division of Wildlife Resources
Wildfires can cause significant disturbances to terrestrial and aquatic ecosystems. Impacts of wildfire are highly variable; some areas experience only modest changes and are quick to recover while other areas incur profound changes to aquatic biota, in-stream habitat, water quality, watershed hydrology, hillslope erosion, and sediment transport. While the biota of some streams recover very quickly (e.g., 2-4 years), in other cases, the trajectory of recovery can be very slow and take decades. Further, in some cases, these impacts only affect areas within or near the burned area, while in other cases the impacts are propagated far downstream. At present we have very limited ability to predict which parts of the landscape, and thus which populations of fish, are most likely to be negatively affected by fire. Similarly, we have little basis for projecting ecosystem recovery and prioritizing areas for fish populations. Such knowledge could inform future pre-fire forest and fish conservation management practices as well as post-fire burned area emergency response efforts and stream restoration/rehabilitation practices. We are studying the area burned by the 2010 Twitchell Canyon fire as a case study to understand post-fire landscape and biotic response, towards a goal of informing future management of both landscapes and fish in the face of fire. This project will address four general interdisciplinary questions: 1) Based on the geomorphic setting and combination of fire, rainfall and other environmental variables, why were some creeks more impacted than others? What are the most meaningful metrics to quantify impacts? 2) How significant was the landscape response from this event compared with other wildfires in the same area and how do erosion rates estimated from this event compare to the long-term (millennial-scale average, i.e., natural background) rates of erosion? 3) What is the trajectory of biological and physical recovery and does it vary predictably within and among streams? 4) Using the environmental and biological data available, can we generate a predictive model of post-fire ecosystem response, which accounts for effects of the North American monsoon, at the landscape level?