Dear Paddlewisers, I’m sure there are some experienced navigators out there who might help with this. Is it generally true that where a tide stream runs through a bottleneck, such as a narrow entrance to a widening bay, slack water in the bottleneck will not coincide with either high water or low water? Peter Treby *************************************************************************** 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/ ***************************************************************************
Peter Treby wrote: > Is it generally true that where a tide stream runs through a bottleneck, > such as a narrow entrance to a widening bay, slack water in the bottleneck > will not coincide with either high water or low water? Yes. Depends on size of the bay relative to the narrowness of the neck. Slack water will occur when the relative levels of the bay and "ocean" outside the bay are the same height (ignoring the effect of momentum of the tidal stream). OTBE, this will be somewhere close to mid-tide, and may only occur for a very short time. This is discussed in David Burch's book on kayak navigation, and Bascom's Waves and Beaches, also. -- 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/ ***************************************************************************
Dave Kruger writes: > OTBE, this will be somewhere close to mid-tide, and may only occur for > a very short time. This is discussed in David Burch's book on kayak > navigation, and Bascom's Waves and Beaches, also. Funny you should mention Willard Bascomb just now. I was watching a National Geographic program last night when his name came up. It seems he wrote another book that inspired Robert Ballard, the discoverer of the Titanic, to look for ancient shipwrecks in the Black Sea. (The depths of the Black Sea being poisonous to marine life, Bascom speculated that it might be possible to find intact wooden hulls on the bottom.) When Ballard found a 1500-year-old (or was it 1500 BC?) shipwreck last year that had an intact mast still standing over the deck, he immediately phoned Bascom with the news only to find out that Bascom had died two days before. Chuck Holst *************************************************************************** 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/ ***************************************************************************
Peter, etal, This month's "The Industrial Physicist" magazine, http://www.tipmagazine.com/ , has an interesting article about using computer modelling to define tide variability, http://www.tipmagazine.com/tip/INPHFA/vol-7/iss-5/p14.pdf The author is Derek Goring, the principal scientist of the Coastal Hydrodynamics Group of the National Institute of Water and Atmospheric Research Ltd. in Christchurch, New Zealand (d.goring_at_niwa.cri.nz). --allan (In Vermont our tides are minimal and the water is getting harder ;[ ) On Thu, 8 Nov 2001 16:13:26 +1100, Peter Treby wrote: >Dear Paddlewisers, >I’m sure there are some experienced navigators out there who might help with >this. >Is it generally true that where a tide stream runs through a bottleneck, >such as a narrow entrance to a widening bay, slack water in the bottleneck >will not coincide with either high water or low water? > >Peter Treby *************************************************************************** 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/ ***************************************************************************
>This month's "The Industrial Physicist" magazine, >http://www.tipmagazine.com/ has an interesting article about using >computer modelling to define tide variability, >http://www.tipmagazine.com/tip/INPHFA/vol-7/iss-5/p14.pdf > >The author is Derek Goring, the principal scientist of the Coastal >Hydrodynamics Group of the National Institute of Water and Atmospheric >Research Ltd. in Christchurch, New Zealand (d.goring_at_niwa.cri.nz). I've heard Derek speak a couple of times and give a Power Point presentation of some tidal flows - http://www.niwa.cri.nz/pgsf/CASHCANZ/peninsula.html http://www.niwa.cri.nz/pgsf/CASHCANZ/cook.html If you hunt around a bit more on the site you will probably find the flow round New Zealand (anticlockwise). Lyttelton, which is the port for Christchurch has one spring tide a month and I believe there is one other place in the world with this. The area effected is from a bit north of Timaru to somewhere near Kaikoura so there's a fair bit of open coast i.e. not caused by constricted waters. The tide heights from tide to tide are not a "smooth" sine wave but quite ragged. Off the coast in front of Christchurch there is also a surge every 40? minutes, quite small about an inch or so if I remember correctly. > >Is it generally true that where a tide stream runs through a bottleneck, > >such as a narrow entrance to a widening bay, slack water in the bottleneck > >will not coincide with either high water or low water? Then there can be the effect of the surge (top of the tide) going in and coming out giving a couple of small peaks. Alex . . *************************************************************************** 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/ ***************************************************************************
It will be slack water at the mouth of the bay when the water depth on either side of the inlet equalizes. Because of the constriction at the mouth, which impedes the exchange of water between the bay and the ocean, equal depth will not occur at high or low tide but at some time in between. Richard Smith *************************************************************************** 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/ ***************************************************************************
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:33:24 PDT