Rising rivers, rising costs

It’s all about a pile of dirt. Oh, and some armour stone, too. But mostly dirt.

This year, it’s Newfoundland and Labrador’s pile of dirt. But it’s coming to Prince Edward Island and Nova Scotia, and New Brunswick as well.

It’s because, when it comes to weather, the ground is moving. Oh, and the water’s rising.

In St. John’s, the provincial government is preparing to build a wall. Not, like Donald Trump, to keep immigrants out, but to hold the floodwaters back.

What’s being planned is a floodwater berm 480 metres long and covering some 2.6 acres, to stop what environmental reports suggest could be the “inundation” of the province’s only tertiary care hospital, the Health Sciences Centre.

The project’s in the environmental planning stage right now – three years ago, when planning started, the construction cost was expected to be $283,400.

Leary’s Brook is hardly remarkable. More an urban stream than a river, it’s hemmed in by marsh and small spruce, by battered peach-leaf willow and stunted birch.

In most places, it’s only about 10 feet wide, and sports discarded shopping carts and tossed bicycles, the low-hanging branches on both sides hung with torn drapes of ragged plastic bags.

There are ducks, brown trout, osprey and gulls, and most of the time, it’s a pleasant enough flow of fresh water.

But the brook drains a large watershed, including paved mall parking lots and ranks of subdivision houses in areas that used to be water-absorbing forest. That means lots of water can move downstream quickly – and, as the province has seen in recent years, even more water than is usually expected.

That’s because, as the environment changes, storms sweeping up from the south are bringing more and more tropical moisture, and much higher rainfalls than infrastructure designers ever expected.

That’s led to a change in what planners call the 100-year feature: designing systems to withstand the peak storm or rainfall that can be expected in 100 years. (In Cape Breton, they’d call that 100-year event Thanksgiving 2016 – parts of Sydney saw 219 millimetres of rain fall that day, making it the wettest day since records started being kept in 1870.)

That kind of rainfall would convert little Leary’s Brook to a torrent, completely covering a nearby thoroughfare, flooding hospital utility tunnels and potentially flooding the hospital itself.

Changes to flood flows on that small urban river are remarkable; while it was thought that the 20-year peak at a bridge just above the hospital was 47.3 cubic metres per second, the new flow is almost half again as high: 68.2 cubic metres per second. In the hundred-year storm model? Possible flow rates have risen from 64.4 cubic metres per second to 91.9 cubic metres per second.

The hospital is not alone in deciding to move forward with construction to deal with increased flooding.

The City of St. John’s is considering berms all along Leary’s Brook and in other parts of the associated Rennie’s River watershed.

The city is also building a weir to allow it to use a pond on the river, Long Pond, as a catchment to hold floodwaters during peak rainfalls.

The cost? Around $4.5 million, give or take, depending on which option the city chooses, on top of the quarter-million-dollars being spent to protect the hospital.

It’s good urban planning, but it’s something else as well: it’s considerable spending and a tacit admission that the times, and the weather, are a-changing.

And that means taxpayers are going to have to find the cash necessary to help keep basements dry, and rivers somewhere close to their courses.

The alternative, as Sydney can attest, can be even more expensive – by Dec. 8, the cleanup price tag there was already $15 million. And climbing.