Liem Bahneman <liem_at_starfleet.com> wrote: >> 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 35 knots. It was moving so fast that when it came around the bend about a mile away, it was _leaning_. >> I know that section of the Columbia and have paddled it several times. I am pretty sure I have camped and lunched on the beach in question. A couple of observations: 1. 35 knots is excessive. Large cargo vessels do not attain such speeds on the Columbia for sure, and I doubt many are capable of that speed on the open sea. 20 knots would be a maximal figure and 15 knots is a common maximum speed on the Columbia. Looking at the bow wave of the container ship in question, I'd guess that ship is travelling at about 13-15 knots. 2. I have experienced the drawdown/surge effect many times, and it is more entertaining than threatening except when the bottom configuration focuses its effect. And, that's what happened to Liem's party. I do not want to minimize the hazard of these surges, but Liem's numbers are suspect, nonetheless. I have never seen a drawdown/surge with an eight foot excursion. All the ones I have seen maxed out at about 3 feet, with maybe the odd four-footer here or there. In any case, even a 3-4 foot excursion is dangerous if you do not anticipate it. Many beached power boats on the Columbia have been slammed around by them. What makes them really nasty is that they cause a long horizontal displacement of the water's edge on a shallow beach, which could catch little kids unawares and knock them down, with injuries certain and a drowning a possibility. They make the usual ship's wake look puny. -- Dave Kruger Astoria, OR *************************************************************************** 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/ ***************************************************************************
Liem Bahneman <liem_at_starfleet.com> wrote: >> 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 35 knots. It was moving so fast that when it came around the bend about a mile away, it was _leaning_. >> That is an impressive video, Liem. Really appreciate your making it available to us. It was worth the long download. (I'm on dialup.) I've paddled that stretch of the Columbia several times, and I'm pretty certain I have lunched or camped on that same beach. And, I have experienced those surge waves many times. However, I don't think that ship could have been doing 35 knots. That speed is beyond the capabilities of ships of that type, I believe, and cargotainers do not run that fast in the shipping channel on the Columbia. The maximum speed for ships there is about 20 knots, with the nominal speed more like 13-15 knots. In addition, the bow wake in one of the photos looks like what a ship doing 10-13 knots would make. None of this is intended to minimize the effects of the surge/drawdown, however. I have seen many surge/drawdowns on the Columbia with vertical excursions of 3 to four feet. An 8 footer is not beyond possible, but I've never seen one that large. Even a 3-4 footer is a hazard because on a shallow sloping beach like the one shown in the video, the runup is enormous, and a smaller person could get bowled over and swept a long ways. To make them even more tricky, the drawdown precedes the surge, so some folks run out when the water drops, fascinated by the exposed sand, much like what a tidal wave (sic; tsunami) causes on a sloping beach. Buddies of mine who are unfamiliar with these always pooh pooh me when I warn them about ship wakes, but it only takes one shot, and they become believers. I've seen power boats in the 15-20 foot range that were stranded very high and dry by surges, and I have enjoyed surfing a couple. They are fun for the initiated, but dangerous for those who do not expect them. -- Dave Kruger Astoria, OR *************************************************************************** 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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