7 September 2011 CBPOA MEETING – Carrie Barron, Surrey’s Drainage Engineer
Subjects addressed (specific to Crescent Beach)
A. Drainage, Sea Levels, Storm surges
B. Earthquakes, Tsunami, Liquefaction, Slope Erosion (affecting train tracks)
A. Drainage, Sea levels, Storm surges
The present drainage system doesn’t cover all of Crescent – it will gradually be replaced. The new pump station will be liquefaction-proof.
The ground water table level is rising and will continue to rise as sea levels rise. The current prediction is for a rise of .67 metres (or 2 feet) by 2100. Our land is sinking, and storm surges will be bigger. Storm surges occur mainly in Dec. and January.
The South end of Crescent is more vulnerable to wave action than the North end of Crescent. The dykes at the South end, therefore, are higher at 3.6 metres (11 feet). Areas around the Serpentine and Nikomekl rivers may see up to 2 metres (or 6 ½ feet) rise during storm surges.
The Province will update this information every 5 years – and dykes will be raised accordingly.
B. Earthquakes, Tsunami, Liquefaction, Slope Erosion (affecting train tracks).
No one really knows the “when or where” of the next major earthquake affecting this area. Vancouver Island may not protect us from tsunami. And there may be amplification as a tsunami travels through the smaller islands. There is a debate about the height of the tsunami. Present predictions for this area are 2 metres (6 ½ feet) – but no one really knows for sure. And it is not necessarily the initial tsunami wave alone that will create damage. All of these events could create a lot of damage.
Crescent Beach is in an area that is in a “high to very high” zone for liquefaction as we have soft sandy soils and a high water table. Soils lose their strength and stiffness in response to earthquakes. Our buildings may well sink.
Regarding slope damage above the BNSF tracks – all new building plans will be subject to Geotechnical tests. The details related to older buildings are hard to police. The slide at 123rd street will be mitigated by a deep – tunneled pipe drain. Presently, there is a temporary pipe.
BEST ADVICE: AFTER A LARGE EARTHQUAKE GO TO HIGH GROUND AS QUICKLY AS POSSIBLE. STAY UNTIL THE “ALL CLEAR” ADVISORY and use portable radios to tune into local stations:
CBC 690 AM or /88.1 FM
CKNW - 98 AM
CKWX - 1130 AM
