Subsurface Flow in a Shallow Soil Canadian Shield Watershed

Past studies in Canadian Shield headwater catchments have identified the importance of subsurface flow mechanisms in generating storm runoff. Recent work in the Muskoka-Haliburton region of south-central Ontario has suggested that subsurface flow within hillslopes with shallow soils occurs primarily along impermeable bedrock surfaces. Two trenches were dug on the side slope of a small headwater catchment and instrumented to measure flows at different levels in the soil. Results show that flow over the bedrock surface constitutes the largest component of hillslope discharge during fall rain storms. Peak discharge and recession rates for bedrock surface flow hydrographs were synchronous with channel discharge. Calculations show that this component of hillslope flow could account for the majority of peak discharge during storm events.