Philip Round in Canada.com: Experts probing why the Tsolum River has been running so high in recent years have concluded it's mainly because it's raining more heavily and frequently than in the past. Suggestions that the impact of logging operations might be contributing to much greater run-off from the watershed "cannot explain the occurrence of high flows on the Tsolum River in 2009 and 2010."
But they acknowledge that assessment is based on available information, particularly from TimberWest itself, about changes to its forest management practices over the past 50 years. Northwest Hydraulic Consultants (NHC) was commissioned to conduct the detailed flood hydrology investigation of the watershed by three partners who shared the cost - Comox Valley Regional District, the City of Courtenay and TimberWest Forest Corporation. Its final report will be presented to the regional district this afternoon (Tuesday).
Local governments got involved because of concerns over more frequent flooding in Courtenay and why it might be happening. Around 2010 there were what NHC call "three flood events" involving the Tsolum - one of them the biggest in 46 years of measuring flows. But having analyzed available statistics, the consultants found the Tsolum was not unusual in carrying huge quantities of water at that time.
"There have been a number of large floods on the east coast of Vancouver Island during the last five years that have either been the largest or second largest over the period of record," the report notes. "These include floods on the Tsolum, Puntledge, Oyster, Quinsam, Englishman, Cowichan and Koksilah Rivers." And having compared the data for several rivers between Duncan and Port Hardy, NHC concludes: "The recent upsurge in flooding is closely associated with extreme precipitation events."...
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