Scientists warn about outdated flood-risk maps

Leafing wistfully through pictures of her flooded home, Marie Nason can now joke about her misfortune.

"I called it my river view," she says of the three feet of water that inundated her yard and filled her basement. But the flood that hit Fredericton in 2008 was no laughing matter and scientists predict events like it will only become more frequent. 

As governments spend billions cleaning up the aftermath of events, such as Hurricane Sandy and the Alberta floods, scientists say more money should be invested in mitigating and preventing the ravages of such disasters.

Located half a mile from the St. John River, Nason and her husband knew their house was on a floodplain when they bought it, but they decided to take their chances.

Still, Nason says the flood took them by surprise.

"It went from no water around our house in the morning to completely surrounded by afternoon," she says.

"My husband is looking out the window going like, ‘It's coming in the driveway,’ and like, ‘It's coming up really fast, we need to get out of here or we won't be able to get out.’ We basically had to leave and just hope and pray that it didn't come in."

Yet the water made its way through the foundation, causing tens of thousands of dollars in damages to the property.

Nason says people should never have been allowed to build in the area.

"Get us out of here," she says.

"This used to all just be farmland. Back when it was just farms and cows and stuff, people just moved the livestock to higher ground. But when your house is here, you can't really move your house."

New mapping tools

Flood-risk maps used by the provincial government and communities are in the process of being updated, according to Darwin Curtis, the executive director of the Department of Environment and Local Government’s climate change secretariat.

"We’re developing new technologies and tools to augment what’s already on the ground," says Curtis.

He says the provincial government has started mapping key areas using Light Detection and Ranging (LiDAR), which uses lasers beamed down from planes or helicopters to measure land relief with incredible accuracy.

However, Curtis says implementing the LiDAR data to enhance existing flood-risk maps and effect legislative change is a long and expensive process.

Tim Webster, a research scientist and flood-risk mapping expert at the Nova Scotia Community College, says LiDAR will provide communities with important information.

'As that science improves, we need to continuously update our flood-risk maps or revise them, if you will. So we look at what areas will be vulnerable not only today, but in the future.' — Tim Webster, flood-risk mapping expert

"We have a much more detailed terrain model that we can then impose different water levels on and very precisely determine where that water will go and what extent will flood because of this underlying high accuracy of the elevation model," Webster says.

"As that science improves, we need to continuously update our flood-risk maps or revise them, if you will. So we look at what areas will be vulnerable not only today, but in the future."

Still, Webster says LiDAR is only one piece of the puzzle and that fully understanding flood risk also depends on hydrometric data, such as measurements of river discharge and tide gauges.

Unfortunately, he says, cuts made to the Canadian hydrometric program have resulted in years of lost data on water patterns, which prevents scientists from identifying trends.  

"Maybe people didn't see the value of this monitoring program, but I think we're sort of paying the price now," says Webster.

"We can't go back and look to see how often these events happen, the precise elevation that the water got to, how the atershed has changed, the behaviour of the hydrology."

Environmental audits

The last available audit of the federal hydrometric program dates back to 2010 and echoes Webster’s concerns: "Based on documentation reviewed and interview results, the size and structure of the hydrometric network is considered insufficient for the overall characterization of water resources in Canada."

The audit goes on to say that, "climate change also results in data becoming outdated where there are significant shifts in the hydrological signal. All these needs require consideration of climate variability and change and it is this issue that underpins the most pressing need for improved data collection in Canada."

A spokesperson for Environment Canada told CBC News the national hydrometric program has since been audited again and is "in the process of implementing a risk-based approach to its network design."

Webster says there is a tendency for governments to be more reactive than proactive.

"Often times, just like with Sandy, they knew there were certain areas of New York and New Jersey that were vulnerable, but still infrastructure was built there, homes were built there," he says.

"It's only after a big storm that people kind of wake up and say, or politicians wake up and say, wow, we need to do something about this. We need a study to determine the vulnerability, we need an adaptation plan to try and mitigate from this happening again."

Mapping and adapting

Identifying floodplains is a big part of community planning and flood-risk maps shape zoning policies to help protect residents and business owners by dictating what — if anything — can be built in vulnerable areas.

In 1976, the federal Flood Damage Reduction Program was created to assist Canadian communities in creating flood risk maps.

New Brunswick was the first province to sign on and in the 1980s maps were created in 13 areas, with the provincial government and municipalities each contributing one third of the cost.

Depending on the region, the comprehensive maps were built using hydrometrics (the measurement of water movements and patterns), topographic data and information on historical flood events to delineate where water levels had risen in the past.

Brian Burrell, a former hydrotechnical engineer for the New Brunswick government, helped create some of these first flood-risk maps.

He says he still remembers the date each map was created.

"Lower Fredericton Lincoln was designated in 1982, in February. Oromocto Jemseg, that came out in 1981, in March," he says.

Burrell says there are various tools to help people deal with flood events, but that flood-risk maps are the fundamental first step in protecting people.

"Flood forecasting is directed to help people move away from the floodplains, but they can’t relocate all their buildings, all their materials. Flood-risk maps were there to help people avoid being there in the first place," he says.

Burrell says there have been some updates to the maps — mostly outlining the reach of the most recent flood events — and they still serve a useful purpose for residents and planners. But he cautions that more exhaustive updates are necessary. 

"These maps are old," Burrell says.

"Whether that flood-risk area is as large as it should be is not something that I don’t think anybody really knows for sure at the present time."

He says many of the statistics with which the maps were built were contingent on environmental conditions remaining the same over the years.

However, with climate change and rising sea levels altering the Atlantic landscape, this has not been the case.

"There would be some reason to re-examine that hydrometric records and produce new flood risk maps," says Burrell. 

In a report prepared by the Atlantic Climate Adaptation Solutions Association (ACASA) , the environmental effects predicted for New Brunswick include wetter spring and fall seasons and more frequent "extreme" weather events, including hurricanes and storm surges.

What’s more, researchers at the Massachusetts Institute of Technology and Princeton University have recently found that powerful storms once deemed one-in-100 year events could now happen every three to 20 years. This could increase the risk of floods.

"Homes and businesses could be threatened due to their proximity to the coast, or their location in floodplains or water runoff paths," the ACASA report warns.

Changes require community support

In New Brunswick, Curtis says the process of updating flood-risk maps and adapting zoning legislation to newly identified risks requires community buy-in.

He says the costly preventative measures can be a tough sell: "Sandy might not happen for another 50 years. No one knows for sure. So how much money do you put into these things?"

But Webster said there have been some positive improvements.

"The government is moving ahead, unfortunately it seems to be in rather piecemeal fashion and the emphasis now seems to be a lot on changes in policy," Webster says.

"They are not concentrating so much on doing the fundamental mapping on a systematic basis to cover all the regions that are at risk."