|Satellite view of sediment plumes from the Fraser River meeting Georgia Strait
|Fraser River delta and floodplain 10,000 years ago
|Fraser River delta and floodplain 5,000 years ago
|Fraser River delta and floodplain today
|Aerial view of 1948 flood
While much of the dredged sand & silt is in turn used in land reclamation projects, and sorted for various uses by sand & gravel companies, a good portion is added to the edge of the river delta itself. However, as less and less of the delta is being maintained for farm use, and more of it is being used for housing needs and expanded port infrastructure, the risk has now shifted from one of flood to one of slope failure on the outer edge; an underwater landslide as it were. It has happened before and it could happen again, and the forces that could cause this range from ocean wave activity to an earthquake.
Earthquakes pose special problems for the Fraser delta because conditions are perfect for liquefaction to occur. Liquefaction is a phenomenon caused by earthquake shaking which turns loose, water-saturated sediment into a fluid (liquefaction). When sediments liquefy, the ground may subside irregularly, causing buildings that are not properly anchored to tilt or collapse. So, try as we may to control the Fraser River with dykes and dredging there are still many unintended consequences to factor in our plans. In the meantime I'll just wait for the muddy waters to settle like they always do and then things will be clear again.