Big Dollars Needed For Flood Mitigation

Monday, May 25, 2009 08:49 PM

Areas awash in light blue are the highest risk areas of flooding in Prince George, whether it be from an ice jam event on the Nechako, or the spring freshet on the Fraser.

Prince George, B.C.- The final report on flooding in Prince George and ways to mitigate damage from floods presents several options, but they come with a high price tag, and no guarantees.

There will need to be a new flood plain level established, as the event of the 2008 ice jam blew the old flood plain marks right off the map. That will mean new construction regulations for some areas of the city.

The experts say what they have learned is that in order to create an ice jam event, you need flows of more than 200 cubic metres per second in the Nechako during 20 days of temperatures that are -5 or colder.

The report presented to Prince George City Council this evening, outlines that dredging the Nechako is not a viable option. “I know that will come as a surprise to many” says Monica Mannerstrom, Senior Engineer with Northwest Hydraulic Consultants “Gravel extractions can be effective for lowering flood levels in some rivers, but that would not be the case in Prince George.” She says you could remove enough gravel to fill a 25 storey building in a football field, and there would still be an ice jam “”Removing gravel would increase flow areas, which would reduce velocities and encourage more ice to accumulate.” However, the report says there is merit in widening the channel at Cottonwood Island to carry some flow during an ice event, and there is merit in making a similar channel on the north side of the river.

While the full suite of range of mitigation options carries a price tag of $35.4 million dollars, the total has been whittled back to $32.6 million for the following five most important actions:

Dike along North side of River Road $15.5 million
Land Use changes along P.G. Pulpmill Road (land expropriation $9.3 Million)
Enlarge the Cottonwood Island Flood relief side channel $3.0 million
Raise Preston Road and Build a short dike $1.2 Million
Land use changes (expropriation or flood proofing of buildings) in the following areas
- South Fort George near Paddle Wheel park $1.4 million
- Morning Place $1.4 million
- Lansdowne south end $0.8 million

Mannerstrom says no matter what options are taken, there are no guarantees, “You could build a dike to the new 200 year flood plain level, and next year be hit by a 500 year level flood.”

The next stage will be public consultation carried out by the Fraser Basin Council .There will be public open houses, and submissions accepted on line . The hope is to have all the information ready to return to Council this fall for some decisions on action.

City Engineer Dave Dyer says that’s when the next budget process will determine if there can be funding found for some of the mitigation works. The City has applied for funding for design work for a dike and the enlarging of the Cottonwood Island channel, but has not yet heard if those dollars will be provided.

In any event, if the proper conditions exist next winter, there won’t likely be any mitigation work done in time to spare the city from an ice jam flood.

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Posted on Monday, May 25, 2009 08:49 PM in News by 250 News

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Comments

Posted by: hammmy on May 26 2009 3:30 AM

$32.6 million to dredge a few kilometers!
All I can say is WOW

Posted by: acrider54 on May 26 2009 5:44 AM

Oh well the taxpayer has loads of money

Posted by: onemansthoughts on May 26 2009 7:45 AM

What a total bunch of idiots, yes, all they have to do is dig out around the bridge and the junction of Nechako and the Fraser rivers. It can be done in the fall when the rivers are at an all time low. It would take maybe 2 weeks.Any of our old time loggers could do this, but nope we have all these educated experts, that cant garantee that the 32 million pricetag will work.
Hey Ben, jump on this so we can dredge that
river this fall. Take care all.

Posted by: metalman on May 26 2009 8:22 AM

I second the proposal put forth by 'onemansthoughts'
It is too bad that a common sense solution like that can never fly if any level of government is involved.
metalman.

Posted by: seamutt on May 26 2009 8:47 AM

Ah just build the new cop shop and PAC on stilts.

Posted by: Loki on May 26 2009 4:32 PM

I see no reason for appropriation or mitigation.
Anybody dumb enough to buy or even live by a major tributary, especially on a known flood plain has bought their own problem. Not the tax payers problem.
The only real problem is that this was and still is actually permitted.
Change the bylaw to forbid any habitation, occupation or daily year round business.

We are no longer tied to the river as a transportation route.

Posted by: Palopu on May 26 2009 8:23 PM

Seems to me that this study is flawed in a number of ways.

One part of the study states that the ice in the Fraser River starts to form 30 km South of the Nechako, and the ice backs up to the Nechako thus causing the ice jam. Sounds pretty good if you say it fast, however during the last ice jam, the river south of the Nechako was open water. In fact the ice breaker from Quebec was put in the water at Paddle Wheel Park and worked its way up the Fraser and into the Nechakos North Channel. The water South of the Simon Fraser River Bridge was also open.

So it would appear that we had a ice jam on the Nechako West of the conflueance, and we had open water South of the confluance.

Another statement ;put forward was that even if you did the dredging it would not make any difference, because the dredged space would just fill up. The rational is that you can only put so much water into the Fraser River. They also state that the removal of gravel, increases flow areas, reduces velocitys, and you get more ice accumulation.

There are a number of things wrong with this statement; One is that in the next paragraph they state that there is some merit it widening the channel at Cottonwood Island and making a similiar channel on the North side of the river. Now wouldnt making these channels wider, increase flow areas, reduce velocitys, and cause more ice accumulation????

There are other things open for discussion however I doubt if anyone would pay any attention to them anyway. After all we are not ****Experts***

Insofar as the amount of water than can be put into the Fraser River. Where the hell do you suppose the water went before they built the Kenny Dam. To make a statement that you can only put so much water into the River is goofy.

The whole idea behind dredging the Nechako and Fraser was to increase the depth to a level that would allow the ice to flow freely down river. As it is now, during the winter the ice piles up on the gravel that has accumulated over the years, and starts to jam. This in turn causes the flooding.

Have a nice day.