Mitigating erosion risk from enhanced soil water repellency following wildfire

Wildfires can reduce the wettability of soil (i.e. increase their water repellency), accelerating runoff and erosion that in turn can cause flooding, landslides and aquifer contamination. Our NERC-funded research carried out following severe wildfires in Sydney’s main drinking water supply catchment area, has revealed a link between fire severity and soil wettability. This work has led to substantial changes in the policy for mandatory post-fire assessments by the United States Forest Service (USFS). Moreover, this practice is being increasingly applied elsewhere, including Canada, Australia and parts of Europe, all of which now include specific consideration of soil wettability following severe fires and are underpinned by the methodology we developed. Based on these assessments, landscape-rehabilitation is applied at high-risk areas following wildfires, to limit the threats to life, property, infrastructure and ecosystem quality arising from excessive runoff and erosion. In 2012, for example, ~1.3 million hectares of burned land have been assessed in the USA using the new post-fire assessment guidelines.


Wildfires 1Top: Landscape following a severe fire in conifer forest, USA (Image, S. Doerr)

Wildfires 2Bottom: Post-fire debris flow, USA (Image, R. Leeper)