Sunday, November 27, 2016

The Danger of Ocean Inlets

Umatilla, FL



A headline in today's news, prompted this post. It was,
7 dead, 1 missing in New Zealand fishing boat disappearance.   It was a story about a charter fishing boat that sank while trying to come in the inlet of a very big harbor.

As you know, Libby and I had 30 years of sailing expierience before setting out on Tarwathie.  We did mostly lake sailing, but I also sailed a lot in the Baltic Sea, and we chartered boats in the British Virgin Islands three times.  One would think that is plenty of experience.  Wrong.

One of the many things we learned the hard way in our first few years, was how dangerous ocean inlets are for boaters.  In most cases, we advice newbie cruisers to, "Just get out there and do it."  Inlets are an exception.  We advise them to avoid almost all inlets except in the mildest possible conditions.   No amount of inland sailing experience can ever prepare you for what happens at inlets.

The biggest and most destructive danger at inlets is the waves.  Waves build up at inlets because the water is becoming more shallow.  That is magnified greatly by sandbars which preferentially form exactly at the inlet where ocean waters meet harbor waters.  It is doubly magnified when strong tital currents are funneled in/out through narrow inlet openings and the wind is in the opposite direction.   That combination creates huge standing waves.

It sounds as if today's report from New Zealand was a case of the boat being swamped by a wave as it tried to cross the sandbar. 

In the Bahamas, when the waves at the inlets are big, the locals call it "the rage."  Almost any vessel and any crew experienced or not are in danger of being destroyed or killed by defying the rage.  

Tarwathie is a Westsail 32, one of the most rugged and seaworthy boats ever made.  She has been tested to the limit by conditions we encountered at inlets.  There have been several other occasions when I reversed course and refused to challenge conditions at an inlet.

So what do you do if you are out at sea, and you want to enter a harbor?  You must pass the inlet to enter the harbor.  First choice, is to choose one of the safer inlets.  In the USA we call them class A inlets.  They are wide enough, and deep enough, and many have jetties, to mitigate the worst effects.   New York City's outer harbor is the best example I know of a safe inlet.  For years, we used only Class A inlets.  In later years, we used lesser inlets, but only in the right conditions.  Read here about one of the times I chickened out.

When you travel up/down the ICW, every inlet you pass is a source of shoaling, and shoals that change a lot from week to week.  The Corps of Engineers dredges the shoals ceaselessly, but it can't keep up.

A contributing factor is that GPS chart plotters and paper charts, usually don't show any details at the inlets.  It is a blank area on the chart.  They do that because the details change so fast.  An outdated chart is worse than no chart.  We found one book, 
Inlet Chartbook to Southeastern United States, that is an enormous help for the SE. We have not seen similar books for other areas.  But even that book appears to not be updated since 2005.

Advice to cruising sailors.  The seamanship of your vessel and crew will likely meet their maximum challenge at inlets.

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