Friday, May 23, 2008

River forecasters have water on the brain

By Tom Hawthorn
Special to The Globe and Mail
May 22, 2008


On the fourth floor of a Victoria office building, a small crew spends long working days crunching numbers.

They have figures for rainfall and for temperature and for water level and for snow water equivalent, which means the amount of water in a snowpack.

Up in the mountains, a season's worth of snow has at last started to melt. The water will follow gravity to the mighty rivers that course through the province.

The folks at the River Forecast Centre have the job of figuring out whether those rivers are likely to course through your bedroom.

They have water on the brain at this time of year.

This is freshet flood season. Allan Chapman, the centre's head, is on permanent duty, bad news just a pager's buzz away at any time of day. Or night.

He and his crew have the awesome responsibility of issuing alerts about rising water levels. Given enough time, dikes can be reinforced and homes evacuated. But if the data are misread, or interpreted too late, the outcome can be far different.

“We're not very good if we provide warnings after floods have happened,” he said, his humour dry in a way the province is not.

Mr. Chapman worked all through the holiday weekend, issuing advisories and offering updates on the radio and through press releases. He took a few minutes yesterday to offer a tour of a grandly named workplace that consists of some cubicles and his tiny office, dominated by topographic maps of British Columbia.

“People think we've got a floor of an office tower with banks of computers,“ he said. “But there's just the five of us.”

This was supposed to be a calm year, coming after record snowpacks in northern British Columbia in 2007. The snowpack was close to normal, which means it was neutral in the centre's parlance. No drought, no big flood risk.

In April, though, the mercury seemed stuck. Warm weather did not come. It was one of the coolest Aprils in a century. Sunshine and warmth proved elusive in May, as well.

“We got to May 14 and we really had not melted any snow,” Mr. Chapman noted. “That all changes the risk factors.”

The snowpack was not so neutral after all.

The first melting took place on the Victoria Day weekend. The centre warned the public to be careful when rafting, fishing or camping. The water on many rivers was running fast and cold. On the Cowichan River, a young man from Mexico fell off a raft and could not be found after a two-day search.

Mr. Chapman knows of one other drowning and notes another dozen people were saved in rescue operations. No search-and-rescue teams, more deaths. No River Forecast Centre, even more deaths.

He can tally the fatalities from flooding in this province from memory. He knows what catastrophic damage can result from a major flood. He knows he'd better be correct when interpreting the data.

“That's part of the weight we carry,” he said.

Mr. Chapman, 53, grew up on a small farm where the western limits of Winnipeg met the prairie. He walked to school along a mud path beside a drainage ditch and would often build dams and otherwise play with running water.

The 1950 Red River Flood was a common topic of conversation when he was growing up, so he was aware at a young age of the devastating power of a river spilling its banks.

As he got older, he and his friends played along the banks of nearby Sturgeon Creek, where they caught crayfish and cavorted at water's edge. When he was 11, his best friend drowned in the creek, showing how even a pastoral idyll could be treacherous.

He earned a science degree at the University of Winnipeg and a master's at Trent University in Peterborough, Ont.

Prognostication is for soothsayers. These folks are scientists. The science of hydrology is complex, the equations mind-boggling.

The crew at the centre – river forecast hydrologist Luanne Chew, snow survey specialist Janis Wright, snow instrumentation specialist Steve Corner, and a computer technician – are busy this week running numbers for an important snow bulletin update.

These figures are reported by people who trek by snowmobile and snowshoe to isolated spots that house instruments in buildings looking like “wooden outhouses,” as one of the crew said, as well as by automated stations that beam information to the staff via satellite. These snow pillows, as they are called, are large rubber bladders filled with antifreeze. The pressure on the fluid is measured, giving a figure for the snow water equivalent at the location.

Those numbers will determine what warnings will be issued, which officials alerted, which residents evacuated.

In Prince George, a flood warning update for the Upper Fraser River was given yesterday morning. The river was expected to crest at about 9.55 metres after rising overnight.

This morning, they will be looking at the numbers yet again.

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