Flooding The Lower Mainland is considered to have a high vulnerability to flood risk. There have been two major region-wide floods in
1894 and
1948, both associated with an extreme
spring freshet of the
Fraser River. Other major floods in the Lower Mainlandincluding June 1972, November 1990, and November 2021have been more localized, primarily impacting areas in the Fraser Valley like the
Sumas Prairie, with comparatively minor impacts to Metro Vancouver. Prior to the 2021 flood, according to the Fraser Basin Council, scientists predicted a one-in-three chance of a similar-sized flood occurring in the next 50 years. In the second quarter of 2007, the Lower Mainland was on high alert for flooding. Higher than normal snow packs in the
British Columbia Interior prompted municipal governments to start taking emergency measures in the region.
Dikes along the Fraser River are regulated to handle approximately at the Mission Gauge (the height above sea level of the dykes at Mission). Warmer than normal weather in the province's Interior region caused large amounts of snow to melt prematurely, resulting in higher-than-normal water levels, which, nevertheless, remained well below flood levels. Flooding can cover much of the Lower Mainland.
Cloverdale,
Barnston Island, low-lying areas of
Maple Ridge, areas west of
Hope,
White Rock,
Richmond, parts of
Vancouver, and parts of
Surrey are potentially at risk. In 2007, the Lower Mainland was largely spared, although northern regions of the province, along the
Skeena and
Nechako Rivers, experienced floods.
Climate scientists predict that increasing temperatures will mean wetter winters and more snow at the high elevations. This will increase the likelihood of snowmelt floods. The provincial government maintains an integrated flood hazard management program and extensive flood protection infrastructure in the Lower Mainland. The infrastructure consists of dikes,
pump stations, floodboxes,
riprap, and
relief wells.
Earthquakes While
earthquakes are common in British Columbia and adjacent coastal waters, most are minor in energy release or are sufficiently remote to have little effect on populated areas. Nevertheless, earthquakes with a magnitude of up to 7.3 have occurred within of the Lower Mainland. Based on geological evidence, however, stronger earthquakes appear to have occurred at approximately 600-year intervals. Therefore, there is a probability that there will be a major earthquake in the region within the next 200 years. In April 2008, the
United States Geological Survey released information concerning a newly found
fault south of downtown
Abbotsford, called the Boulder Creek Fault. Scientists now believe this fault is
active and capable of producing earthquakes in the 6.8 magnitude range.
Volcanoes Much of the Lower Mainland is vulnerable to
explosive eruptions from the
Garibaldi Volcanic Belt. Volcanoes in this zone are capable of producing large quantities of
volcanic ash that may cause short and long term water supply problems for Lower Mainland communities. All airports covered by the accompanying
eruption column would be closed, heavy
ash falls would damage electrical equipment and weak structures could collapse under the weight of the ash. ==Communities==