Fraser River delta sinking faster than imagined

Startling new research from the Geological Survey of Canada shows that Vancouver International Airport and other large facilities along the lower reaches of the Fraser River delta are falling below sea level much faster than previously imagined.

The airport could find itself more than 130 centimetres below the high-tide mark in the Strait of Georgia by the end of the century - and research indicates that low-lying land along the Fraser as far upstream as Maple Ridge and Langley are also sinking.

Studies this year by the Intergovernmental Panel on Climate Change predict a sea level rise of about 16 centimetres by the end of the century due to global warming - water expands as it gets warmer.

The difference for communities along the Fraser delta - and a handful of coastal venues in Canada - is that they sit on soft land that is sinking under its own weight.

When you couple rising seas with sinking land, you get a double whammy in terms of future threats to urban development as the ocean's high tides creep farther inland.

The data shows that the weight of a building is the critical factor - single-family homes aren't facing the same kind of impacts, according to Stephane Mazzotti, a Sidney-based researcher with the Geological Survey of Canada.

In a telephone interview, Mazzotti said the Fraser delta is "subsiding" at a "background rate" of one to two millimetres per year - compounding a global average sea level rise of 1.6 millimetres per year, or 16 centimetres by 2100.

But Mazzotti said the average number belies greater impacts in some areas of the delta that bear a heavy load of human activity - even where methods such as preloading construction sites with large amounts of earth are expected to settle them prior to construction.

"Some areas are experiencing faster subsidence - up to five millimetres per year and higher - due in part to heavy construction loads," he said.

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