REPORTING · 12th February 2013
A presentation came before Council from Doctor Brian D. Bornhold from Prince George and he spoke too the topic of landslides and tsunamis in Douglas Channel. He told Council this was going to be a brief presentation and there would be a longer one at the Community Advisory Board the following night.
“I’ll be talking about the study of landslides and tsunamis in Douglas Channel which the Enbridge Northern Gateway has undertaken, studies we’ve undertaken over the past 7 years,” said Bornhold.
He told Council a large team of Marine Geologists, Geophysicists, Geo-Technical Engineers and Numerical Modellers from UBC and the University of Alberta was put together. They undertook a review of Pacific Basin Tsunamis from all over the Pacific to see what they would look like when they got to Kitimat. Then, they interpreted Eco Sounding data collected by the Canadian Hydrographic service to find if there was any evidence of past underwater slope failures.
They undertook a geophysical survey to find the thickness of the sediments and find any areas of failure. Finally, they looked at the Moonbay failure of 1975.
“There is no tide gauge in Kitimat during the period when there were very large Tsunamis, for example, 1964 when the Alaska Tsunami, but there were studies undertaken by the department of fisheries and oceans in 1988 which modeled the anticipated amplitudes of the heights of these waves and the periods from several source areas around the Pacific,” said Bornhold
The highest anticipated tsunami would come from an area in Alaska, where there has not been an earthquake in many years and experts estimate would be the most likely location for a devastating earthquake. A magnitude 9 earthquake there would give Kitimat a slow raise of sea level with a wave height of 2 metres within 1 hour.
However, the Enbridge Project will be monitoring alerts from the Northwest Tsunami Warning Centre located in Hawaii and Alaska.
The study looked for underwater instances of landslides as well. Bornhold stated they only found two events which took place 6 months apart due to a major flood in 1974 and some work being done in Moon Bay the following year. Both created tsunami’s.
Bornhold showed a cartoon of what Kitimat Arm looked like under the water. He pointed out both of the slides and told Council they did not fail all at once, but were from multiple slides, only two of which generated tsunamis. He added they do not see anything of this scale in the rest of Douglas Channel.
They used the data as well as several tools to see what such a slide would look like at the proposed dock and created four scenarios with different volumes and properties. The study provided the results to Engineers who are designing the docks for the Enbridge project. The Engineers have told them the results would not have any consequences to the vessels which were birthed there. Bornhold showed the Council what the waves would look like.
The team looked around Kitimat Arm to find polygons of what could potentially produce tsunamis. They rated them on a scale of possible to very likely. All of them fell into the lowest two categories. He added there were areas they would like to look into a second time but they were unlikely to generate a tsunami with a slide.
“None of the results included the possibility of human error during construction activities elsewhere. If somebody else undertakes construction in the Kitimat Arm and overloads the foreshore for example, or dredges trigger a tsunami which has not been accounted for in the assessments, one of the important conclusions is, in the opinion of that team I mentioned at the beginning, natural underwater slope failures large enough to generate large tsunamis in the Kitimat arm are unlikely to occur,” said Bornhold.
He stated this is based on historical evidence, two events they have identified and human activities. The Enbridge Project could deal with the waves from the event in 1975. He stated it was important for all activities around the Kitimat Arm to be regulated so there is nothing that could trigger a large failure in other areas.
Mayor Joanne Monaghan thanked him for the presentation. Councillor Mario Feldhoff wanted to know about the buildup of sedimentation which gets released into the mouth of the Kitimat river. Bornhold stated traditionally, the distributaries of the deltas move back and forth across. Sediment moves down the face of the delta.
However, in Kitimat, the delta has been taken out of its natural regime so the river distributaries cannot migrate over the natural delta. Bornhold told Council the sediment will build up and it will fail. This will not generate a tsunami.
Councillor Rob Goffinet asked for further information on the investigation. He was told it will be a look at what it is made of, whether it is stable, how thick it is and will it will fail. Goffinet wanted to know when it was done. Bornhold stated they are planning them now and it will take place later this year.
Councillor Edwin Empinado asked for more information about the study from 1975. He was told during the first event the sediment carried through the channel undercut the slope. Because the channel could not migrate freely, the slope failed causing a tsunami. In 1975, the construction of a roto-terminal led to a failure.
There were no further questions so he left the meeting.
let your gaze be world embracing
Comment by Sandy on 1st April 2014
For those that are really trying to be objective and just in their decision on this proposal to build the twin pipeline from the oil sands and shipping the bitumen and condensate in and out of Kitimat. Please look at situations around the world where the oil and gas extraction industries have beaten the population into submission. At this point in time they are using glossy and shiny promotional media to achieve their end, when that appears to be failing they use the courts. Really look at the power differential here. We have the power to slow them down and to stop them if we want to, if we are not completely convinced. Let's not cave in to promises.
Lituya Bay Alaska!
Comment by Thomas Campbell on 16th February 2013
Lituya bay Alaska tsunami Look it up. 5 tsunamis in the last 150 years. The largest was caused by a landslide...... (Holds the record for the highest ttsunami)
Believe nothing of what you hear & only half of what you see
Comment by Larry Walker on 12th February 2013
Pls somebody....correct me if I am wrong but the Douglas Channel flows from the North East in a South West direction before entering "open water"
To me, this means a quake in Alaska would have less affect on the channel than one just off the North tip of Vancouver Island.