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Fraser River flood risk in Mission decreases; city packs up Tiger Dam

Last week’s forecast predicted a 1-in-100 year flood on Thursday
City workers deflating the Tiger Dam that was set up along the eastern edge of the Mission City Dike. City of Mission photo.

The flood risk from the Fraser River has decreased from last week, and the City of Mission has packed away the Tiger Dam protecting the weakest points in its dikes.

On June 29, B.C. government’s River Forecast Centre predicted the Fraser freshet would reach a once-in-100-year levels in Mission on July 7; as of July 6, the risk has decreased to between a once-in-five year, and once-in-10 year levels.

RELATED: Fraser River forecasted to reach 1-in-100 year levels in Mission on July 7

With the better forecast, the Tiger Dam was deflated and packed up on July 6, said Taryn Hubbard, manager of communications with the City of Mission.

“We are working within our flood preparedness and response plan and are monitoring the situation closely,” Hubbard said. “We won’t return (the Tiger Dam) for another week, just in case we need to put it up again if the river levels rebound.”

The Tiger Dam was lent to the city by the province, Hubbard said. The dam is a series of water-filled tubes over a metre high, anchored into the pavement to create a barrier to floods.

It was deployed along the easternmost end of the 3.5-kilometre Mission City Dike over the weekend near Harbour Avenue and Horne Street.

The Mission City Dike protects nearly 100 commercial and industrial properties along 370 acres of floodplain, and at its weakest point, its over two metres below the flood construction level (FLC).

A report on the state of Mission’s dike system was presented to city council in June.

All of the city’s dikes were given “sub-standard” ratings in the provincial 2015 dike assessment, and portions were rated as unacceptable.

The Mission City Dike has six points below the FLC, and has not had any upgrades since 2011. Staff have said that in the event of a major freshet, a “major mobilization” would have to occur to temporarily dike around 700 metres.

The Silverdale dike is in even worse shape. It runs 4.1 kilometres, protects 570 acres of mostly agricultural land, and has 15 points in the dike where it does not meet the FLC.

RELATED: State of Mission’s diking systems detailed in report

RELATED: Building Mission ‘superdike’ likely requires developer land assembly


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