淡水沙崙海灘傳出學生結伴到海邊戲水，有8人被浪捲走。我無從判斷是被何種浪或是「離岸流」 給帶到外海。但是從 Google Map 的衛星圖中，似乎可以發現到「離岸流」的蹤跡。
What are rip currents?
Rips are strong, narrow currents that flow from the shoreline seawards through the surf. They exist as a way of getting water carried to the beach by breaking waves back out to sea and usually sit in deeper channels between shallow sand bars. The bigger the waves, the stronger the rip. Think of them as “rivers of the sea”.
Types of rips
• Fixed rips are the most common and occur when waves are smaller or haven’t changed in a while. They appear as dark gaps between areas of whitewater.
• Flash rips are bigger and occur when waves have increased suddenly. They appear as more turbulent areas of water.
• Headland rips are fixed rips that are often permanent and occur next to headlands and structures such as groynes (防波堤) and jetties (突堤,防波堤,碼頭).
Are they dangerous?
Rips are only dangerous if you don’t understand what they are and you are not a good swimmer. They can carry you more than 50 m offshore in less than a minute and are the major cause of
surf drownings and rescues in Australia. However, surfers use rips to their advantage to help them get back out to the waves.
How do you spot a rip?
Since rips often sit in deeper channels between shallow sand bars, always spend 5-10 minutes looking at the surf for consistent DARKER and CALMER areas of water that extend offshore between the breaking waves. Rips also carry things so look for moving sand, seaweed, foam and people!
What should you do if you get caught in a rip?
• The most important thing is DON’T PANIC. The rip won’t pull you under the water, it will just carry you seaward.
• NEVER swim against the rip. Stay afloat, go with the flow and signal for help.
• Don’t get caught in one! Make sure you understand what rips are and ALWAYS swim between the flags on patrolled beaches.
Fast Facts about Rips
• On long beaches in NSW and QLD, rips occur approximately every 200 m.
• Rips flow fastest around low tide.
• Rip flow increases rapidly (pulses) shortly after wave sets break.
• Even small rips can flow faster than Olympic swimmers!
• Rips often look like the safest place to swim....they’re not!
以上說明摘自以下網址連結之文件。版權仍屬於原所有者(可能是 Dr. Rob Brander 或 UNSW, Australia)。
edited: 01:49 am, Nov. 27, 2012
update: 10:23 pm, Jul 27, 2012
02:28 am, Jul 24, 2012