BC
More than half of Fraser River dikes would overtop in repeat of 1894 flood, new modelling showsLONG READ
Gordon Hoekstra , Nathan Griffiths -
In March 2017, under the then-B.C. Liberal government, the province announced $10.5 million to upgrade the Nicomen Island dikes.
Although the dike is under the authority of a diking district with a volunteer board, the province provided the money to the Fraser Valley Regional District to administer on behalf of the diking district.
Some of the funding is expected to be used to upgrade five pumping stations, while other funds may be used to widen and raise some of the dike system, said Fraser Valley Regional District spokeswoman Angelique Crowther.
A 2015 report estimated the cost to upgrade the entire Nicomen Island dike system to modern standards would be $65 million.
In Delta, there are sections of its dike system in the Ladner area that were found to overtop in various flood scenarios, according to Postmedia’s analysis.
Suman Shergill, manager of utilities and engineering for the city, said due to the community’s proximity to the ocean, its dikes are built to withstand a 200-year winter coastal flood, which produces higher water levels than a spring freshet.
The city did not say whether it had received the latest dike crest-flood scenario information from the Fraser Basin Council and had checked the figures on the ground.
Following last year’s deadly flooding that caused billions of dollars in damage, B.C. municipalities and First Nations have been calling for the province and Ottawa to show more leadership on flood protection.
The November flooding was caused by an atmospheric river, a torrential downpour in a short period of time. This is different than a spring freshet but also expected to increase in frequency and severity because of climate change.
B.C. government officials noted they had funded the latest work of the Fraser Basin Council, saying the information was provided mainly for local governments to prepare for the freshet along the Fraser River.
But Andrew Giles, manager of the River Forecast Centre and flood safety for the province, said the information also supports longer-term planning by dike authorities through the four elements of emergency management: preparedness, response, mitigation and recovery.
“This information also provides a foundation for further dialogue between the province and diking authorities toward flood risk reduction,” said Giles.
The federal government referred questions about the new dike information, and what it meant for its plans, to the province.
ghoekstra@postmedia.com
twitter.com/gordon_hoekstra
Yesterday
Vancouver Sun
This low, overgrown dike, left, in Maple Ridge would be no match for a major flood.
In May of 1894, rapid snow melt triggered a massive flood from the upper Fraser Valley to Richmond. Homes, barns and bridges were swept away and railway tracks were left twisted from the deadly flooding.
The flood was the largest on the Fraser River since settlers arrived. But because the population was so low, the value of property damages was not great, perhaps a half-million dollars by one estimate.
Today, a similar event would have a much different result.
A Postmedia analysis of information recently provided to Lower Mainland municipalities shows more than half of the dikes along the lower Fraser would overtop in a repeat of 1894, inundating homes and businesses in towns and First Nation communities, and vast swaths of farmland.
The data provided to Metro Vancouver and Fraser Valley municipalities — and to Postmedia at its request — used the latest dike crest survey information produced by the province in 2019 and 2020 and was applied to five flood scenarios, ranging from the 1894 flood, considered a one-in-500-year event, to a one-in-20-year event.
The data for 100 dikes was produced by the non-profit Fraser Basin Council, which is helping co-ordinate a Lower Mainland flood strategy with municipalities, the province and Ottawa.
The new information is meant to help communities prepare for spring high-water levels on the Fraser, known as a freshet, and to influence longer-term plans to improve flood resiliency as climate change is expected to make flooding more frequent and severe.
“It’s one piece of the puzzle,” says the Fraser Basin Council’s director of water programs, Steve Litke, who presented the information to a recent meeting of the Metro Vancouver flood-resiliency task force.
© Jon Murray Steve Litke of the Fraser Basin Council.
“Obviously, the crest height of the dike is significant, a pretty important part of a dike functioning properly relative to different flood events. … This does reveal deficiencies in terms of height,” said Litke.
The latest information does come with caveats.
The analysis focuses on the spring freshet and does not include potential flooding from coastal storm surges or flooding from other rivers — and as a result does not include all the dikes along the lower Fraser.
The Fraser Basin Council has cautioned local governments the information should be checked on the ground for measurement errors or situations where some feature such as adjacent high ground provides flood protection.
Litke said he believes the biggest limitation is the fact there are other ways that dikes can fail before overtopping, including erosion and seepage. “So, that’s an additional concern that isn’t reflected in these results,” he said.
© G.W. Edwards
In May of 1894, rapid snow melt triggered a massive flood from the upper Fraser Valley to Richmond. Homes, barns and bridges were swept away and railway tracks were left twisted from the deadly flooding.
The flood was the largest on the Fraser River since settlers arrived. But because the population was so low, the value of property damages was not great, perhaps a half-million dollars by one estimate.
Today, a similar event would have a much different result.
A Postmedia analysis of information recently provided to Lower Mainland municipalities shows more than half of the dikes along the lower Fraser would overtop in a repeat of 1894, inundating homes and businesses in towns and First Nation communities, and vast swaths of farmland.
The data provided to Metro Vancouver and Fraser Valley municipalities — and to Postmedia at its request — used the latest dike crest survey information produced by the province in 2019 and 2020 and was applied to five flood scenarios, ranging from the 1894 flood, considered a one-in-500-year event, to a one-in-20-year event.
The data for 100 dikes was produced by the non-profit Fraser Basin Council, which is helping co-ordinate a Lower Mainland flood strategy with municipalities, the province and Ottawa.
The new information is meant to help communities prepare for spring high-water levels on the Fraser, known as a freshet, and to influence longer-term plans to improve flood resiliency as climate change is expected to make flooding more frequent and severe.
“It’s one piece of the puzzle,” says the Fraser Basin Council’s director of water programs, Steve Litke, who presented the information to a recent meeting of the Metro Vancouver flood-resiliency task force.
© Jon Murray Steve Litke of the Fraser Basin Council.
“Obviously, the crest height of the dike is significant, a pretty important part of a dike functioning properly relative to different flood events. … This does reveal deficiencies in terms of height,” said Litke.
The latest information does come with caveats.
The analysis focuses on the spring freshet and does not include potential flooding from coastal storm surges or flooding from other rivers — and as a result does not include all the dikes along the lower Fraser.
The Fraser Basin Council has cautioned local governments the information should be checked on the ground for measurement errors or situations where some feature such as adjacent high ground provides flood protection.
Litke said he believes the biggest limitation is the fact there are other ways that dikes can fail before overtopping, including erosion and seepage. “So, that’s an additional concern that isn’t reflected in these results,” he said.
© G.W. Edwards
The Fraser River flood in Hatzic, B.C., in June, 1894.
Postmedia used the information to estimate how much of each dike would fail in the five flood scenarios, which also include one-in-200, one-in-100 and one-in-50-year floods.
That information was then used to calculate the percentage of all the dikes where at least some section of dike was expected to overtop in the five flood scenarios.
In addition to the more than 50 per cent that would overtop in a flood similar to the one in 1894, the Postmedia analysis showed a section of more than one-third of the Fraser River dikes would overtop in a one-in-200-year flood, 20 per cent in a one-in-100-year flood, 16 per cent in a one-in-50-year flood and more than 10 per cent in a one-in-20-year flood.
Postmedia also examined information on whether dikes met the province’s guidelines for a buffer between the high-water mark and the top of dikes, known as freeboard. The guidelines call for a 0.6-metre buffer for the one-in-500-year flood.
The data showed 83 per cent of dikes had some sections that did not meet this guideline.
Craig Hodge, a Coquitlam councillor and vice-chair of the Metro flood-resiliency task force, said the latest dike crest-flood scenario modelling helps support work on a Lower Mainland flood strategy and underscores the need for funding and the urgency to get started on dike improvements.
During the catastrophic flooding in November, even though Coquitlam was not flooded, the community was affected, for example, by cut off transportation routes and gas rationing. The deadly flooding in the Fraser Valley and B.C. Interior washed away homes, bridges and roads and resulted in the evacuation of 14,000 people.
“We just have to bring everybody together. Certainly there’s a clear need to co-ordinate flood management strategies,” said Hodge. “Now, we know we can’t wait.”
Communities where there are significant portions of dikes that would overtop in the flood scenarios include Maple Ridge, Mission, Delta and Nicomen Island in the Fraser Valley, which includes a community of the Leq’รก:mel First Nation.
In the City of Maple Ridge, nearly 90 per cent of the 2.5-kilometre Albion dike would overtop in the one-in-500-year flood, with seven per cent of it overtopping in a one-in-20 year event. Almost all of the dike does not meet the province’s freeboard guideline, according to Postmedia’s analysis.
City officials said the Albion dike is not owned by the city, but it has been carrying out work at the request of the province.
City spokesman Fred Armstrong said the city has the latest Fraser Basin Council figures and had conducted its own surveys, which have helped influence the city’s freshet flooding plan.
“In the event of potential inundation of the areas, the city’s freshet flooding plan has an interim plan to place concrete blocks along the edge of the river to act as a temporary dike until such time as a permanent dike would be completed,” said Armstrong.
The city has said it is willing to take ownership of dikes in the city but not until the province provides funding for upgrades to current standards, which also need to be part of a comprehensive plan along the Fraser River, noted Armstrong.
The Lower Mainland flood strategy was meant to set flood mitigation priorities, costs and a cost-sharing model but is four years overdue. Hodge, the Metro flood-resiliency task force’s vice-chair, said it is still probably at least one year away.
Work carried out earlier for that flood strategy estimates a similar 1894 flood today would cause about $23 billion in damage and result in severe economic fallout.
These latest flood scenario figures underscore the significant undertaking needed to improve flood protection on the lower Fraser — and the struggles local governments and First Nations have to do that.
A recent Postmedia News investigation found that municipalities don’t have the billions of dollars needed to upgrade flood protection after the province downloaded responsibility to municipalities beginning in 2003.
In Mission, analysis showed 16 per cent of one of its dikes along the Fraser River, largely protecting commercial property, would over top in the one-in-500 year flood, 10 per cent in the 200-year event and six per cent in the 100 year event.
More than 20 per cent of the dike doesn’t meet the freeboard guidelines.
City of Mission spokeswoman Taryn Hubbard said they received the Fraser Basin Council data and have used it alongside other reports and studies to influence their work and planning. A recent report on the state of Mission’s dike system found they are “deficient” with issues such as being lower than design flood levels, and pumps not having enough capacity.
In the Fraser Valley, Nicomen Island’s dikes also face overtopping in flood events. About 90 per cent of the 35-kilometre dike system would overtop in a one-in-500 year event, according to Postmedia’s analysis. And none of the dike meets the province’s 0.6 metre freeboard guidelines.
Postmedia used the information to estimate how much of each dike would fail in the five flood scenarios, which also include one-in-200, one-in-100 and one-in-50-year floods.
That information was then used to calculate the percentage of all the dikes where at least some section of dike was expected to overtop in the five flood scenarios.
In addition to the more than 50 per cent that would overtop in a flood similar to the one in 1894, the Postmedia analysis showed a section of more than one-third of the Fraser River dikes would overtop in a one-in-200-year flood, 20 per cent in a one-in-100-year flood, 16 per cent in a one-in-50-year flood and more than 10 per cent in a one-in-20-year flood.
Postmedia also examined information on whether dikes met the province’s guidelines for a buffer between the high-water mark and the top of dikes, known as freeboard. The guidelines call for a 0.6-metre buffer for the one-in-500-year flood.
The data showed 83 per cent of dikes had some sections that did not meet this guideline.
Craig Hodge, a Coquitlam councillor and vice-chair of the Metro flood-resiliency task force, said the latest dike crest-flood scenario modelling helps support work on a Lower Mainland flood strategy and underscores the need for funding and the urgency to get started on dike improvements.
During the catastrophic flooding in November, even though Coquitlam was not flooded, the community was affected, for example, by cut off transportation routes and gas rationing. The deadly flooding in the Fraser Valley and B.C. Interior washed away homes, bridges and roads and resulted in the evacuation of 14,000 people.
“We just have to bring everybody together. Certainly there’s a clear need to co-ordinate flood management strategies,” said Hodge. “Now, we know we can’t wait.”
Communities where there are significant portions of dikes that would overtop in the flood scenarios include Maple Ridge, Mission, Delta and Nicomen Island in the Fraser Valley, which includes a community of the Leq’รก:mel First Nation.
In the City of Maple Ridge, nearly 90 per cent of the 2.5-kilometre Albion dike would overtop in the one-in-500-year flood, with seven per cent of it overtopping in a one-in-20 year event. Almost all of the dike does not meet the province’s freeboard guideline, according to Postmedia’s analysis.
City officials said the Albion dike is not owned by the city, but it has been carrying out work at the request of the province.
City spokesman Fred Armstrong said the city has the latest Fraser Basin Council figures and had conducted its own surveys, which have helped influence the city’s freshet flooding plan.
“In the event of potential inundation of the areas, the city’s freshet flooding plan has an interim plan to place concrete blocks along the edge of the river to act as a temporary dike until such time as a permanent dike would be completed,” said Armstrong.
The city has said it is willing to take ownership of dikes in the city but not until the province provides funding for upgrades to current standards, which also need to be part of a comprehensive plan along the Fraser River, noted Armstrong.
The Lower Mainland flood strategy was meant to set flood mitigation priorities, costs and a cost-sharing model but is four years overdue. Hodge, the Metro flood-resiliency task force’s vice-chair, said it is still probably at least one year away.
Work carried out earlier for that flood strategy estimates a similar 1894 flood today would cause about $23 billion in damage and result in severe economic fallout.
These latest flood scenario figures underscore the significant undertaking needed to improve flood protection on the lower Fraser — and the struggles local governments and First Nations have to do that.
A recent Postmedia News investigation found that municipalities don’t have the billions of dollars needed to upgrade flood protection after the province downloaded responsibility to municipalities beginning in 2003.
In Mission, analysis showed 16 per cent of one of its dikes along the Fraser River, largely protecting commercial property, would over top in the one-in-500 year flood, 10 per cent in the 200-year event and six per cent in the 100 year event.
More than 20 per cent of the dike doesn’t meet the freeboard guidelines.
City of Mission spokeswoman Taryn Hubbard said they received the Fraser Basin Council data and have used it alongside other reports and studies to influence their work and planning. A recent report on the state of Mission’s dike system found they are “deficient” with issues such as being lower than design flood levels, and pumps not having enough capacity.
In the Fraser Valley, Nicomen Island’s dikes also face overtopping in flood events. About 90 per cent of the 35-kilometre dike system would overtop in a one-in-500 year event, according to Postmedia’s analysis. And none of the dike meets the province’s 0.6 metre freeboard guidelines.
In March 2017, under the then-B.C. Liberal government, the province announced $10.5 million to upgrade the Nicomen Island dikes.
Although the dike is under the authority of a diking district with a volunteer board, the province provided the money to the Fraser Valley Regional District to administer on behalf of the diking district.
Some of the funding is expected to be used to upgrade five pumping stations, while other funds may be used to widen and raise some of the dike system, said Fraser Valley Regional District spokeswoman Angelique Crowther.
A 2015 report estimated the cost to upgrade the entire Nicomen Island dike system to modern standards would be $65 million.
In Delta, there are sections of its dike system in the Ladner area that were found to overtop in various flood scenarios, according to Postmedia’s analysis.
Suman Shergill, manager of utilities and engineering for the city, said due to the community’s proximity to the ocean, its dikes are built to withstand a 200-year winter coastal flood, which produces higher water levels than a spring freshet.
The city did not say whether it had received the latest dike crest-flood scenario information from the Fraser Basin Council and had checked the figures on the ground.
Following last year’s deadly flooding that caused billions of dollars in damage, B.C. municipalities and First Nations have been calling for the province and Ottawa to show more leadership on flood protection.
The November flooding was caused by an atmospheric river, a torrential downpour in a short period of time. This is different than a spring freshet but also expected to increase in frequency and severity because of climate change.
B.C. government officials noted they had funded the latest work of the Fraser Basin Council, saying the information was provided mainly for local governments to prepare for the freshet along the Fraser River.
But Andrew Giles, manager of the River Forecast Centre and flood safety for the province, said the information also supports longer-term planning by dike authorities through the four elements of emergency management: preparedness, response, mitigation and recovery.
“This information also provides a foundation for further dialogue between the province and diking authorities toward flood risk reduction,” said Giles.
The federal government referred questions about the new dike information, and what it meant for its plans, to the province.
ghoekstra@postmedia.com
twitter.com/gordon_hoekstra
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