---------- Forwarded message ---------- From: Liem Bahneman <liem_at_starfleet.com> Subject: Surge/Drawdown [I sent this to your list but I'm not a member, but I think your member's might find this interesting] I'm not a kayaker, but I found your topic while searching for information about this exciting, yet terrifying effect known as the Drawdown and Surge. We were boating on the Columbia River about 4 miles downstream of Longview WA. We beached my father's boat and were playing on the beach. We noticed a huge cargo ship steaming up river at what had to be at least 35knots. It was moving so fast that when it came around the bend about a mile away, it was _leaning_. Anyways, my dad had enough sense to unbeach the boat before the ship had passed. He did it just in time. As soon as he had the boat away, the water level of the river _immediately_ dropped 4 feet. In fact it happened so fast, we were just staring in awe. The ship was still about half a mile downstream. I started recording the event at this time, mainly to see this effect. No sooner than I started rolling did I pan left/downstream to see the HUGE surge rolling in after the ship had passed. This surge was literally 6 feet higher than the normal water line, and it was almost instantaneous. The recording here goes wild as I'm scrambling to move our shoes to higher ground. In retrospect, and looking at the video when we got home, we saw how much potential there was for disaster when this event occurs. Had our son not been warned to back away, he would have been instantly swept up in an 8 foot surge with extreme upstream currents. I imagine that every time this happens (multiple times a day on this river) that people are caught un awares by the power of the surge produced by a passing ship. Though certain conditions (shore/depth/width) probably must exist for extreme conditions, those not lucky enough to see what's coming probably get soaked. Had my dad not moved the boat, it would have surely been left high and dry. Here's a URL to the video: http://www.starfleet.com/liem/photos/other/Longview_August_1/origs/MVI_3500.AVI Things to note in the video: The pebbles visible on the beach immediately in the beginning were only moments before covered with 18-24" of water, so you can see how much the water had retreated. The ship approaching: http://www.starfleet.com/liem/photos/other/Longview_August_1/tn/IMG_3496.JPG.html Passing by: http://www.starfleet.com/liem/photos/other/Longview_August_1/tn/IMG_3497.JPG.html (To get a feel for how fast that ship was moving, those pictures were taken 34 seconds apart) The waterline before (no pebbles): http://www.starfleet.com/liem/photos/other/Longview_August_1/tn/IMG_3484.med.JPG *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
In a similar vein, a group of us had been playing in surf and ledges when we came around a small island in Casco Bay, found a nice sheltered spot and quasi-rafted up for a water-granola bar break. In the shipping lane about 300 yards out, a substantial container ship was passing outbound. The wakes from these ships are sometimes large, but rarely problematic on deeper water. Somewhat unawares of the immediate underwater topography, we were hanging out right where the ledge abruptly becomes shallower than the channel. Therefore, the fairly innocuous wake I'd been watching roll our way, suddenly reared up to become a 4 foot dumping wave. A few of us yelled "incoming" and most got their boats pointed into the wave. One did not. It lifted him broad beam and threw his boat like a shot put across the bow of another paddler's boat who was facing into the wave. Fortunately, the paddler in the second boat was able to deflect both wave-surf and incoming kayak. All remained upright and uninjured, though slightly rattled and all the more wiser about paying attention to one's surroundings, above and below the water line. -W *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
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