此外,熱帶風暴「海馬」昨晨在廣東陽西、電白交界登陸,為粵西帶來狂風暴雨,當局預測今日粵西地區仍有暴雨。另一熱帶風暴「米雷」,預測將會逼近台灣,並沿福建、浙江北上。台灣中央氣象局指米雷將會持續增強,昨晚發出海上颱風警報,外島蘭嶼的渡輪昨已經停航。福建、浙江昨亦發出颱風預警。作者: Lik 時間: 2011-6-24 10:27
No way la, they are using a 1 year return rainfall in drainage design... Can't help until they update the code... Even if they update the code to 5 year return, IMO, it's still too low... You can still see flooding easily based on these extreme weather...作者: Lik 時間: 2011-6-24 14:18
It all depends... In the old days cities used to have combined sewers (sanitary + storm). In small population area, that won't be a problem. But when the city grows, especially when people start talking about saving water resources and being environmentally friendly, that won't work.作者: lo_pak 時間: 2011-6-24 14:52
本帖最後由 lo_pak 於 2011-6-24 15:12 編輯
Take a look at some new stormwater designs nowadays...
"Here’s a link to some pictures from an airline bulletin board showing flooding at O’Hare Airport in Chicago from the remnants of Hurricane Ike. This plane is taxiing through 18″ of water (I can’t imagine a Cessna doing that!). O’Hare had 6.64″ of rain on 9/13, another 1.44″ on 9/14. From 9/4 to 9/14, O’Hare had 12.59″ of rain.
Which means:
on 9/13, 168mm in 24 hr!! as compared to 50mm in 24 hr at Beijing, go figure...
Even in Vancouver YVR, 80mm in 24Hr (10 year return), no probelmo... . You may see a minor flood when it goes to 110mm.
In facilities like the Beijing Airport, if the sewer design can't handle 50mm in 24hr, it's totally unacceptable... (it's +/- equivalent to the 2 year return in YVR).作者: fy789 時間: 2011-6-24 15:29
I copy a small part of it here, and you can see how much mm an hour is like here in Vancouver as a comparison.
The heaviest rains ever recorded in B.C. triggered mudslides and flooding across the province Monday, closing highways and forcing evacuations on the Lower Mainland and Vancouver Island.
Allan Chapman, head of the river forecast centre for the Ministry of Environment, was paged from his bed at 1 a.m. as virtually every river on B.C.'s south coast began to rise dangerously, the result of record rainfalls.
"At 25 millimetres an hour I don't see how you could breathe. It's like being under water," Chapman said. "And we measured 20 to 25 mm an hour for three hours straight at one point.
20 to 25 mm an hour for "three hours" is a real large rainstorm. The 100-year return for "3 hours" is around 18mm/hr @ YVR.作者: lo_pak 時間: 2011-6-25 11:20
The Beijing international airport is located at the Shunji District (north east of Beijing). The reported rainfall is about 34mm in 24hrs on June 23rd. I believe you haven't checked your info in details.
But to be fair, I cannot find the peak hourly rainfall on that day for that area. If this information is available, we can have a better picture of what's actually happening.
After reading the post, I feel that some of you have confused how to interpret rainfall data.
BTW, the IDF (intensity-duration-frequency) chart can be a bit tricky to understand unless you have studied statistics before.