Wildfires can alter landscapes in a few ways; they remove vegetation that would otherwise provide stabilization and absorption to the ground, and they can alter the soil composition itself. If a fire burns hot enough, or is persistent enough, it can change some compounds in the soil to make the soil hydrophobic. Meaning any heavy rainfall that occurs in the affected area will simply pool on the ground surface, as the soil will repel the water.
Data gaps prevent assessment of most Canadian watersheds: WWF report
Spotty research and inconsistent monitoring have made it impossible to evaluate the health of most Canadian watersheds, a study has found. “It’s still largely unknown,” said Elizabeth Hendricks of the World Wildlife Fund, which has just released its second evaluation of the condition of Canada’s freshwater environments. Hendricks said the report points to the need for standardized, national water monitoring done by local communities.