The effects of climate change and extreme wildfire events on runoff erosion over a mountain watershed

VIC-WEPP model results indicate that SRB streamflow will have an earlier shift in peak flow by one to two months under future climate scenarios in response to a declining snowpack under warming temperatures. The magnitude of peak flow increases with each higher severity fire scenario; and under the highest fire severity, the peak flow is shifted even earlier, exacerbating the effects of climate change. Similarly, sediment yield also increases with higher fire severities for both historical and future climates. Sediment yield is more sensitive to fire occurrence than to climate change by one to two orders of magnitude, which is not unexpected given that our fire scenarios were applied basin wide as worst case scenarios. In reality, fires only occur over portions of the basin in any given year and subsequent years' vegetation regrowth reduces erosion. However, the effects of climate change on sediment yield result in greater spatial heterogeneities, primarily because of the spatial differences in precipitation projections, while fire conditions were uniformly applied. The combined effects of climate change and a possible continuation of increasing fire frequency and severity will compound excess sediment issues that already exist in this region of the intermountain West.