Tuesday, October 5, 2010

We Built This City on Rock, Roll, and Silt

I've been in Metro Vancouver for more than a week now and I'm still looking for a place to keep my stuff, but that's not for lack of options. Based on what I've talked about with others, though, I may be one of the few whose options are influenced by seismic hazard maps. Perhaps that's the nature of the transplant - someone who's lived in the Lower Mainland all their life may well be blasé about earthquake dangers, whereas one of the few things I still retain from high school geography class held on Ontario's stable land was the teacher telling us how Vancouver had a 70% risk of a major earthquake in the next 25 years... and this in the late 1990s, so I don't know if the odds have shortened or what.

Today, I'm not sure where he got that information; the most recent figure I saw was from Maclean's, giving a 10% chance of a major earthquake in the next fifty years, which is really not all that bad for a metropolis in an area vulnerable to megathrust earthquakes. Still, the chance remains that a quake will happen, and that's why I'm looking for places in New Westminster.

Or, more specifically, it's why I'm staying away from the city of Richmond entirely. You may or may not have heard of the place; for those Torontonian readers, it's roughly the North York of Vancouver - a formerly rural area that has, in the last few decades, been transformed by explosive suburban development. Today it has a population approaching 200,000, making it the fourth most populous municipality in British Columbia.

It's also built on land that's full of glacial silt brought down by the Fraser River, mostly deposited within the last twelve thousand years. The problem with this is the danger of liquefaction - that is, when exposed to seismic shocks, "solid" ground with a sufficiently high water saturation would turn into a sludge. This is exactly the sort of thing that happened in Christchurch, New Zealand during the recent earthquake there. Considering the strength of earthquakes that the Lower Mainland is vulnerable to - the last megathrust quake, back in 1700, has been estimated at magnitude 8.7 to 9.2 and is thus well inside the top 10 of most powerful earthquakes in recorded history - it's unlikely that a disaster would be particularly kind to Lulu Island.

This might seem stable, but that ain't necessarily so.

What gets me is that this danger has been known since at least 1997, and I only say that because that's the year a National Research Council Canada study detailing the Fraser delta's vulnerability to liquefaction was published - additional studies go back decades. So the question becomes, why in the hell would Metro Vancouver not dial back the intensity of settlement on, and development of, land that is known to be a geological hazard under conditions that for all we know may be triggered tomorrow? I can understand why the City of Richmond itself would be inclined to brush the threat under the rug - after all, no people moving to Richmond means no expansion of tax revenue - but this seriously strikes me as a failure of government. Hell, in the early 1990s, the GVRD increased Richmond's population cap from 157,526 to 185,000 - and considering patterns of population growth, we'll probably see calls from Richmond to have that cap lifted if it hasn't been already - because, you know, they're not only building suburbs on rich agricultural land ideally placed to provide locally-sourced food to Metro Vancouver, but that land isn't solid either.

Does the city of Richmond tell its residents that they're living on land that may well turn to sludge in an earthquake? I don't imagine consulting seismic hazard maps is a common practice among homeseekers. That's just a weirdness mostly of me.


  1. You're right to be concerned. The rare earthquake we had in Toronto this year was spooky enough for me. The West Coast is just waiting for a big one, but local residents simply pretend it's never coming.

  2. That, or they're shrugging over the inevitability. One hopes that Richmond's authorities are enforcing halfway-decent building codes, given the circumstances.

  3. If you have kids, you might want to check the schools they go to: a lot of GVA schools don't meet modern earthquake standards. Back when the Sichuan earthquake happened, and everyone was blaming the Chinese government for shoddy schools, I did a bit of digging and discovered that GVA schools aren't really earthquake-ready.

    To add further irony, money was made available to upgrade schools, and accepted, and then redirected into other programs (just as the Toronto District School Board redirected ESL funds to keeping pools open).

  4. Disturbing and Appalling are two works for that sort of practice. Although in Toronto's case, the need for improving physical fitness is pretty much proven nation-wide just as much as for ESL classes. The TDSB needs money for both with equal degrees of urgency.