The hydrogeomorphic sensitivity of forested water catchments to wildfire
Wildfires are a strong driver of change in many landscapes (e.g. south-eastern Australia, western USA, Canada, and the Mediterranean). Vegetation removal and changes to soil properties by wildfire result in altered surface hydrology and erosion rates. When wildfire occurs in a water catchment these changes can cause negative impacts on water quality, supply, and treatment. Therefore, being able to predict the potential response of a landscape to wildfire is important in informing resource management decisions.
This research project investigates erosional response of catchments following the 2009 fires in Victoria. This paper details methods and results of preliminary work undertaken on this project. Field surveys were used to quantify error associated with remote identification of channel initiation points (CIP) from aerial photographs. Movement in the CIP is one way of measuring erosional response and post-fire sensitivity. Error in estimating the CIP was found to depend on vegetation cover. The average distance errors for increasingly denser vegetated classes (0-24%, 25-49% and 50-100%) were 23.0m ± 5.5m, 11.1m ± 1.9m and 23.2m ± 4.8m.
A difference in the morphology (area and slope) between catchments exposed to high and low annual average radiation was found. Catchments exposed to higher radiation were found to have, on average, steeper slopes and smaller catchments (16.2° and 16150m2) compared with lower radiation sites (9.6° and 39015m2).
The wider research project will explore the link between dryness (radiation), morphology and post-fire response in future work. These future project outcomes and benefits to resource managers are discussed.