Wildfire impact on the hydrological conditions of an Alpine slope

Wildfire events have severe effects over mountain environments, changing dramatically the local terrain hydrogeological conditions and frequently affecting slope stability. Besides burning vegetation, wildfires induce a modification on soil properties that could result in a decreased capacity of infiltration. This leads to an increase of erosion and, potentially, of the related geohazards, such as flash flooding and debris flows, in the vicinity of the affected sites.

Past studies found that this reduced infiltration rate changes over time and the original hydrogeological soil properties are expected to recover in as long as 10 years after the wildfire event, depending on the environmental characteristics and on the soil properties of the site.

Our work aims to investigate the impact of a wildfire on the infiltration conditions of a slope located in the Southern Alps, considering as a case study a wildfire event occurred in Sorico (CO) in December 2018.

The effects of the wildfire on the infiltration rates and the subsequent recovery of the original hydrogeological properties were evaluated over the span of more than two years after the event. Infiltration tests were performed both within the most affected area as well as in the nearest unburnt area. Results were then correlated with precipitation and satellite imagery data in order to retrieve a recovery factor, necessary for the calibration of a simple 1D hydrogeological model.