CGRG Bibliography of Canadian Geomorphology
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Author : Bender, M.; Wu, S.; Chan-Yan, D.; Bonar, R.L.; and Denney, P.
Date : 2004.
Title : An empirical analysis of flood peak changes due to forest harvesting along the Alberta Foothills.
Publication : Forest Land – Fish Conference II. Ecosystem Stewardship through Collaboration, April 26-28, 2005. Edmonton, Alberta.
Issue :
Page(s) : 137-138.
Abstract
Logging activities in forested watersheds often result in a variety of changes. The magnitude and extent of these changes, however, is highly dependent on the local climate, surfi cial geology, altitude, and other site-specifi c factors. The timing and magnitude of stream peak fl ows is one type of change that is often reported from scientifi c experiments involving paired-watershed studies. Along the foothills of the Rocky Mountains in Alberta Canada, the change in peak fl ow magnitude due to logging has also been empirically-derived from the analysis of gauging station data. The records indicate a direct correlation between peak fl ow magnitude and the percentage of equivalent clearcut area. The scope of the analysis involved the forest management agreement areas near Rocky Mountain House and Hinton Alberta, where detailed watershed and clearcut information was available. This paper presents a multivariate prediction model for design fl ood peaks, and an example application comparing previous peak fl ow predictions. The model provides predictions for the 2-year 25-year and 100-year return period peak instantaneous fl ows, based on catchment area, average catchment elevation, equivalent clearcut area, and road density. Other factors were also considered, but were statistically insignifi cant compared to the selected model parameters. The other factors included: maximum catchment elevation, average catchment slope, average aspect in terms of percent northern or eastern aspect. The example provided is for Hardisty Creek, at Hinton Alberta. Hardisty Creek is a small ungauged catchment, and a design discharge was needed for several culvert rehabilitation projects. Three previous regional analyses provided estimates of the design discharge, but were determined to produce poor results based on historical anecdotal evidence and based on hydraulic model analysis at the culverts. The multivariate model provided a more realistic estimate of the design discharge, and it provided a means of describing the likely changes due to recent logging activities upstream of the culverts. The example illustrates that while the prediction model may not account for any mitigating site-specifi c conditions, it seems to be more accurate for small watersheds compared to traditional regional hydrologic analyses, and that the multivariate model may be practical for the sizing of culverts and bridges.
Bibliography of Canadian Geomorphology