[Paddlewise] Reading the Water - river bars

Dave Kruger's excellent explanation of how tides work when combined with the
flow of rivers made me realize that even though I have done a lot of boating
on tidal waters not much of it was on rivers. At least not much above the
river entrances which, at least in the Pacific Northwest, is often a bar.
And since crossing a river bar is part of reading the water I began to think
of the methods I use to cross them. Over the years I've made hundreds of bar
crossings in everything from a kayak to a sailboat to a fishing vessel to a
Chevron tanker. I was nervous on every single one of them, too but most of
them have been uneventful.

Almost all the river bars that lead into harbors on the west coast of the
USA have been improved with jetties on at least one side and often on both
sides. These jetties help keep the entrances free of sediment buildup by
forming a protected area where dredges can operate as well as providing a
nice aiming point when you are running down the waves and headed in. It's
just amazing how tiny that entrance can look from the wheelhouse of a 30 or
40 foot fishing boat.

Let's see if we can't itemize the variables in a bar crossing and then work
out the methods for dealing with them. These should form a good basis for
input from other paddlers too. :)

First there is the current in the river. This varies according to the
season, recent precipitation, and perhaps water releases from dams upriver.

Second there is the tide. The tidal range here is important as a larger
difference between high tide and low tide results in greater current speed
as the water moves inland.

Third is wind. We all know about wind.

Fourth is something many people don't take into consideration when entering
river bars and that's the currents outside the bar. Generally this current
moves along the shore (and is called the "longshore current"). These can be
somewhat unpredicatable and variable but can reach speeds of over 1 knot.

Fifth is the state of the entrance. This can include areas of shoaling
iwthin the jetties, how long the jetties extend into the ocean, the width of
the entrance, etc.

Sixth is whether you are going out over the bar or coming in over the bar.
These two, like surf landings on a beach, present completely different sets
of problems.

The boat you're in and your ability to handle that boat are other variables.

Hmm... well there may be more but I can't think of them offhand.

First of all: go look. My w/w rule was, "if in doubt get out and scout".
Before you launch walk out to where you have a decent view of the bar and
watch for a while. Note any problems other small craft are having in the
channel. Does the current correspond to what you were expecting (assuming
you checked tides and river flows on the Internet before you left). If the
wind comes up later in the day (a common occurance on the west coast of the
USA) will the current be opposing it?

If you are arriving from seaward you can't get out and go look but you can
get close and stop and watch for a while. I started boating after flying
airplanes and I used to say that one of the nicest things about boating is
that you can usually stop and think things over.

We have already discussed the interaction of tide and river current when
applied to the nether reaches of a river system but the combination of the
two right at the bar is what we're dealing with now. And, in general, less
current is better. I suppose that seems to be a no-brainer but I'm always
surprised at the people who plan their trips to coincide with an ebbing tide
in the spring after a heavy rain. It's safest at slack water but that's only
30 minutes a day. As a rule I try to cross any bar with a flood tide;
especially if there is an onshore wind. And most especially if the entrance
has shoaling.  If I can't cross on a slack or flood I want a low-tidal-range
ebb with an offshore wind. Choices deteriorate after that.

A tide, as has already been explained, is a clump of moving water that is
pulled along by the gravity of the moon (mostly) and the sun (a little).
When this clump hits a beach it causes the water to rise. When it enters a
river, a bay, an archipelago or an estuary it does the same thing but you
see a very noticable current as the water moves farther inland. This tidal
current can - and often does - overcome the river current so that the
current at the river bar flows into the river entrance. And if an ebb tide
can frequently make an otherwise sleepy river current into a raging torrent
at the bar a flood tide can turn a nasty bar into a pussycat by creating a
situation where the water simply rises on the tide with little or no current
in either direction. This is good. It's especially good if there is wind.

I think any wind - from any direction - makes a river bar crossing worse.
But if you must have wind, try to have wind that is not in opposition to the
sum of the tide and river current. We all know what that means: steeper
waves that are closer together. It also greatly increases the chances of
waves breaking across the bar. So as far as I'm concerned the worst time to
cross a river bar is when the wind is blowing onshore, the tide is ebbing,
and the river is chuck-full of run-off water.

The longshore current will not be a factor until you get beyond the entrance
jetties unless your particular river bar doesn't have them. In that case
you'll have to deal with that current about the time you are also dealing
with all the extra sediment both the longshore current and the river current
deposited. The rock or cement jetties protect you from the effects of the
longshore current while you are inside them but once you get out you will
face whatever effects they produce. These currents rarely run much over
about 1 knot but that can produce some interesting waves when the wind is
opposing the current. The longshore currents often change direction with the
seasons and the prevailing wind. Charts are available but it's often best to
ask someone familiar with the area; especially someone who has just come in.

The longshore current presents an especially intriguing set of problems when
you are crossing the bar coming from seaward. It is often very difficult to
tell just exactly which direction the current is setting you and at the
speed we travel in a kayak this can make things pretty exciting if the
current sets you into nearby rocks or onto the jetty. Most harbors (at least
in the USA) have a sea buoy which marks the beginning of the run into the
harbor and I try to make it a rule to start from the sea buoy and keep track
of my heading. In a kayak this may not be feasable especially if the sea
buoy is more than a mile offshore (like the one at the Columbia River bar).
Nevertheless, I try to be alert for the signs of a current setting me into
danger; how the perspective of the entrance changes, if trees and houses no
longer line up, etc.

River bars are known mostly for one overwhelming characteristic; they have
shallow places where waves can break. When the water flows out of the river
mouth into the ocean it slows (or stops) and the load of sediment it carries
is either dropped or transferred to the longshore current. A goodly
proportion is simply dropped right at the entrance forming the river's bar.
This sedimentation also occurs within the confines of the jetty entrances.
In fact, one might almost say that it occurs especially within the jetties
because there is no longshore current to whisk away the sand and deposit it
somewhere else.

This shoaling represents job opportunities for dredging companies and a pain
in the ass to boaters and kayakers. If you have a VHF radio you can often
listen to individual reports for each river bar and they will often have a
phrase "breaks to the north (or south) in the entrance". It always pays to
be aware of where there might be breakers in any area you plan to paddle
through. Especially in the confined area of a jetty entrance. Breakers are
not as difficult to avoid when heading out to sea because you can see them
more easily. Coming in, however, is a different story and a paddler has to
remain alert to the telltale signs of humped up water, spray, and noise.
Where there will be "breaks" (breakers) at the entrance depends on the state
of the tide, the current in the river, the set of the longshore current and
the wind. This is why it's wise to talk to some ashore. At most of the
improved harbor entrances of California, Washington and Oregon the US Coast
Guard has a lifeboat station within sight of the bar and they can often give
boaters a good idea of conditions with a VHF call.

The relatively narrow confines of a jettied entrance is not the safest place
to unexpectedly encounter breakers so it pays to be extra vigilant. But
boaters and kayakers can encounter other obstructions to their safe passage.
One major obstruction would be the very dredges that keep the bar passable
to deeper-draft vessels. At night it can be very difficult to determine
which side of a dredge is the safe side to pass on but it's often not so
easy during the day either. Part of the reason for the problem is the
multiple anchors arrayed around the dredge. Another is the hose and pipe
system used to exhaust the dredged-up sand.  Usually these hoses extend from
the dredge to the nearest shoreline but not always. It can be dangerous to
be set into a dredge by the current without being very sure which side is
the safest side to pass. If you have a VHF radio you can often reach them on
Channel 13 (bridge to bridge) and ask them which side to pass. Just be sure
you understand where their bow is pointing when they tell you "safe passage
to port".

Other vessels can be a hazard in an entrance channel. If there are breakers
no one wants to go through them so all the boats - regardless of whether
they are headed in or out - try to crowd against the side of the channel
with the easiest water. Kayaks can snuggle up pretty close to the jetty
walls but those rocks are plenty hard. The worst part is that smaller boats
tend to travel back and forth at exactly the speed that produces the largest
wake. The confused seas from an active channel entrance can get pretty
exciting.

Another danger to any vessel entering a river bar is the increased chance of
broaching due to wave action. Within the confined spaces of a jettied
entrance a broach in a large vessel can result in the loss of that vessel
and, perhaps, even the lives of some of the crew. In a kayak a broach could
result in a nasty collision with the rock walls of the jetty or a nasty
capsize at a bad time. When crossing bars in a sailboat I try to carry sail
forward of the mast (the jib or the yankee usually) especially if there is
an onshore (following) wind. If this foresail is sheeted tight it will add
some resistance to turning and might make the difference between a turn
that's easy to control and a nasty broach. I have also been known to tow a
warp (a line rigged to form a large "U" behind the boat to add drag) but
this can be risky for a boat that needs its propeller.

In a kayak approach into a jettied entrance and across a breaking bar
deploying the rudder or skeg will add some lateral resistance aft since the
option of adding sail area forward can be pretty limited. The risk is damage
to the rudder in the event of a collision with the jetty walls. With a skeg
deployed the risk could be an inability to quickly maneuver on the wave and
the possibility that the boat could "trip" over the skeg if it side-surfs
down the face of a wave after a broach. I would work hard to stay on the
backsides of any waves and avoid surfing my way up that chute. I love to
surf but I want some clear exit paths.

Of course a lot depends on your kayak and your skills. Many sea kayaks are
designed to track well but that can be a handicap in breakers. While the
kayak may resist the turning forces better in an incipient broach once the
broach has begun it might be impossible to turn the kayak back on course
before you capsize or run into the rocks they make the jetties out of
nowadays. They can be more like rock gardens than harbor entrances
sometimes.


Craig Jungers
Royal City, WA
***************************************************************************
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/
***************************************************************************