Are Past Wildfire Activities Correlated with the Frequency of Different Types of Post-Wildfire Geomorphic Events such as Landslides and Debris Flows

Around the world, the frequency and intensity of wildfire events are rapidly increasing. Such a trend increasingly exposes some communities to the risk of the secondary hazards of wildfire, such as post-wildfire geomorphic events like a landslide and debris flow. To better manage the risk imposed by the secondary hazards of wildfire, a better understanding of the relationship between wildfire activities and the geomorphic events related therewith is necessary. In this paper, the temporal relationship between past wildfire events and the frequency of two different types of geomorphic events (landslides and debris flow) was studied statistically through the conduction of a time series analysis. The analysis conducted using the data created by the construction of a geomorphic event inventory derived from a set of Landsat based land cover classification of the region of the Rocky and Omineca Mountains in the Canadian province of British Columbia ranging from 1986 to 2019, and the wildfire boundary data provided by the Federal Government of Canada. Both a simple linear regression and a Poisson regression were conducted to analyze the relationship between time and the frequency of geomorphic events, with the application of a slope-based stratification. The study has three key findings. The first finding is that overall, there exists a strong negative temporal correlation between the time elapsed since the most recent event of a wildfire and the frequency of post-wildfire geomorphic events. Second, slope appears to be an influential factor for the relationship between wildfire and the frequency of post-wildfire geomorphic events. Third, despite the presence of a strong correlation, time is a very poor variable for explaining the dynamics of the frequency of post-wildfire geomorphic events.