WEYDV-02-065

Hydrologic Simulation of Wildfire on Sawridge Creek
Sponsor: 
Weyerhaeuser Company Limited
Lead Researcher: 
R.L. Rothwell, Watertight Solutions Ltd., Edmonton, Alberta
Body: 
This project was prompted by the interest and concerns regarding the recent occurrence of wildfires in the Slave Lake region, and the history of flooding of Sawridge Creek, which flows through the town of Slave Lake, Alberta. The objective of the project was to simulate the effects of the Agnes Lake wildfire on the flows of Sawridge Creek, and provide a public presentation of the results.

Hydrologic simulations were carried out using the Regional Hydro Ecological Simulation System (RHESSys). The model is a spatial simulation system designed to estimate the spatial patterns of forest productivity, as well as the energy and water budget of watersheds. The Agnes Lake fire occurred in 1998 and burned approximately 25% of the basin. Hydrologic simulations of the effects of the Agnes Lake Fire on seasonal and daily flows of the Sawridge Creek were completed as well as a simulation for the watershed without fire. The hydrologic effects for both scenarios were simulated for a 15-year time series (1980-1990, 1995-1999). Simulating the fire in 15 different years provided an estimate of how the hydrologic effects would vary with changes in annual and seasonal precipitation.

The hydrologic effects of the Agnes Lake fire are not expected to significantly increase major flood events in the Sawridge Creek watershed. Simulated increases to flow were small. A much larger portion of the basin would have to be burned before changes in the magnitude and frequency of flows would be detectable in the Sawridge watershed. Changes in flow following an extensive fire in the watershed would be most noticeable in the small to medium sized flows than in the major flood events.