“The loss of forest cover is directly attributable to increased flood events, both in magnitude and frequency.”
Is there a link between the loss of forest canopies and the intensity, and frequency of floods in BC?
For decades in British Columbia, forest hydrologists have determined that clearcutting has had little to no effect on flood frequency and magnitude. Studies have now determined that the removal of primary forest cover does in fact, have a significant impact on flood frequency and magnitude.
Civil engineer Younes Alila obtained his BSc., MSc., and Ph. D from the Civil and Environmental Engineering Department of the University of Ottawa. Prior to becoming a professor with the UBC Department of Forest Resources Management in 1996, he worked as project engineer for the Greater Vancouver Regional District.
Upon taking up his duties at UBC in Forest hydrology and watershed management, Professor Alila immediately observed that forest hydrology research was using a unique approach, one that was not used in general hydrology. This approach piqued his curiosity and led to extensive research comparing the two approaches.
For nearly two decades Professor Alila, supported by other research scientists, conducted numerous comparative research studies, and have now concluded that in every study, the unique forest hydrology results were diametrically opposite to those of conventional hydrology. Their findings indicate that; 1, forest disturbance affects not only the small and medium but also larger floods; 2., effects can increase with event size; and 3., forest disturbances can affect large floods in small and large watersheds in environments where rain or snow is the dominant form of precipitation.
60 years of clearcut logging have increased the frequency and magnitude of BC floods. These flood waters collect and increase in magnitude as they flow into the major watershed like the Fraser basin.
You can read Alila’s Biography here: Alila, Younes - Faculty Profile - UBC Forestry
I have referenced Professor Alila’s work many times and feel its valuable to summarize it here and provide links to and commentary of his work.
Kim C. Green and Younes Alila 2012
“We illustrate how forest harvesting has substantially increased the frequency of the largest floods in all study sites regardless of record length and this also runs counter to the prevailing wisdom in hydrological science.”
Forests and floods: A new paradigm sheds light on age-old controversies - 2009
Younes Alila, Piotr K. Kuras´, Markus Schnorbus, and Robert Hudson
“We call for a re-evaluation of past studies and the century-old, preconceived, and indefensible paradigm that shaped our scientific perception of the relation between forests, floods, and the biophysical environment.”
“expose a set of flaws of the most fundamental construct in methods that dominated decades of research in forest hydrology and as a result, cast serious doubts on the current state of science on the relation between forest land use and floods.”
“In contrast, the few studies that have used FP, although not commonly cited by forest hydrologists or land use policy advocates, showed how forest removal can increase the magnitude across a much wider range of return periods”
“The forest hydrology community has been misguided by these CP-based research questions for over a century and as a consequence forced a flawed deterministic process understanding on what should have been purely stochastic research questions.”
Living Water Smart in British Columbia:
““Everybody in the science and professional practice within forest hydrology and in all other Sciences have missed out on the deeper meaning of the risk of extremes.” Dr. Younes Alilia, P.Eng, University of BC