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Getting Passed the Bars
Tidal bars are shallow accumulations of silt and sand that naturally occur at the entrance to some of the rivers and harbours in north eastern Pacific.  Americans call this area the Pacific Northwest - but that is a misnomer.  The bars seem to be built up when the Pacific Ocean storms and river flows deposit sand and silt near the river entrances.
 
When the water of the deep Pacific Ocean (hundreds or thousands of feet) meet the shallow bars (at tens of feet) upwelling occurs that causes the surface waters to confused and choppy.  When  river and/or tidal currents flow from a harbour area toward the ocean,  there is resistance to the flow that causes waves to build up.  The resistance causes the waves to get bigger and start breaking - like the waves you see in surfer movies. 

Below are a couple of pictures of the Umpqua River Bar.  Believe it or not, these pictures show the bar when it is opened

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The waves can get worse. When an opposing wind blows against the flow, you get a wind over tde situation that causes BIG and FREQUENT waves.  The water turns real ugly and the number of breaking waves increases.

 

Left is a picture of the safe water at Umpqua River.  The nasty stuff above builds up on the north side of the channel,  but under the right conditions, you can sail by on the south side.

 

 

Breaking waves are dangerous to small boats.  The waves can be as big as the boat and make steering impossible.  The waves can swamp the boat.  The waves can cause the boat go out of control and turn over or broach and sink.

When the water is shallow as it tends to be over the bars,  the waves can be bigger than the water is deep.  That can expose the ocean floor.  I hate it when that happens. 

This is a link to a some pictures of the Columbia river bar acting up.  The pictures are from the Columbia River Bar Pilots Association web site. 
 

It is amazing to come in from a relatively calm ocean and find that on the bar the water is being really nasty.  You are tired from sailing,  it is the end of the day and you are not as sharp as you should be.  You expect to come to shore where you are safe and can relax. 

But if you have to cross the bar,  you can't relax. 

Navigation controls need to be turned up to max and you need to be very careful.  Know exactly where you are and where you are going.  Watch the depth sounder and compare to soundings.  Monitor chart plotters/navigation systems.  Use what ever tools you have to monitor your position.  Strong currents will work to carry you off your charted course into even shallow waters or on to one of the many submerged breakwaters. 

The job of furling sails and preparing for landing will become much harder over the bar because the deck will be pitching wildly.

Life jackets on.  Tethers, harnesses and jack lines in use.  Anchor ready to be deployed.  All moveable gear stowed and secure.

Here are five rules to help pass a bar safely:

  1. The best time is an hour or two before or at high slack tide.  This is when the current is flowing inland but the strong flow has subsided and the water is at its deepest.
     
  2. OK to pass during any time during the flood in settled conditions.
     
  3. OK to pass at low slack tide.  But if the bar is not very deep this will reduce the safety margin.  On a very shallow bar - not a good idea.
     
  4. Crossing on an ebb tide (when the current is flowing out) is not on. 
     
  5. If the wind is, or has been blowing hard against the tide, forget about it.  The bar is closed.
     

Looking from the ocean side you see the backs of the waves and you can not see them break.  So the bar is going to be rougher than it looks.  From the shore side, however you can see the waves and know better what conditions are.

If in any doubt,  call the local coast guard on your VHF and/or listen to the bar reports on the local Wx channels. 

Be prepared for the bar at your destination to be closed.  You should have alternative plans.

So all this adds to the planning complexity for a harbour hopping strategy for sailing south down the West Coast of North America.  Still if you have time and can wait and you have the flexibility to do the odd overnight jaunt,  the harbour hopping approach seems to work just fine.