BarCrossings

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Revision as of 03:15, 7 November 2014

Bar Crossings

The interplay of tidal flux, ocean breakers, offshore winds, and river current makes a bar—the entrance of a river into the ocean—a highly unstable environment. These forces combine in many complicated ways, and stormy seas make them even more unpredictable. The bars of smaller coastal rivers remain in their natural state, shallow and sandy with constantly shifting shoals and spits. They are without jetties or regularly maintained channels. Conditions of these bars change rapidly according to the influences of wind, current, and sea. They are always dangerous. Boaters should not cross them without expert local knowledge. Shallow water at the river’s entrance will ground a boat in the midst of breakers, the worst possible place to be stuck. The larger harbors which have bars do have jetties and regularly maintained channels. Even so, always use caution when crossing these bars.

Generally, slack tide is the best time to attempt a bar crossing because the tidal current is at its quietest and the boater has the most maneuverability. High slack is best because it puts more water between the boat and the river bottom. Low slack is second best. Avoid cross- ing on an ebb tide, when the powerful outward current is reinforced by the river’s flow but often opposed by prevailing offshore winds and ocean swells. Together, these to make the bar even more dangerous by producing waves that rise and break very quickly. Likewise, a strong flood tide reinforced by the wind can propel a boat forward too fast and make maneuvering very difficult. The influence of rivers is generally less during summer and fall, when flows are at their lowest. Most coastal rivers, being rain-fed, are fullest in the winter. On snow-fed rivers the highest waters tend to come in the spring.

Introduction

Shallow sand bars which can form at the point where rivers, creeks, lakes or harbours meet the sea are locations for experienced sailors only. Any channel through such bars can change frequently. Even in apparently calm conditions vessels can be swamped, damaged or wrecked on bars and lives have been lost.

Avoid crossing a bar on a run-out tide when dangerous waves may occur.  Do not attempt to cross a bar without experience and local knowledge. You should spend considerable time watching the bar conditions in combinations of weather and tide.  Always, it is preferred to cross a tricky bar with other experienced skippers before trying it yourself.  When crossing coastal bars, do not lose your nerve in the white water. Once committed, keep going. Trying to turn around in the middle of a bar entrance can be disastrous. Try to take waves as close to head on as possible.

Assessing the Conditions and Preparation for Crossing

Prior to crossing any bar consider the checklist:

• Know the times of the tide and have up-to-date weather forecast regarding wind and visiblity.
• Physically observe the bar conditions and be prepared to cancel or delay the crossing.
• If unfamiliar with the bar, obtain local advice, eg from the local harbor authorities and local mariners.
• If a high risk crossing ask local government (e.g. USCG) or mariners to meet and guide you into the harbor.
• Check boat condition – especially engine systems, steering and throttle controls, hatches and drains.
• Make sure that all loose items are stowed away in lockers or tied down to prevent movement.
• Check that all watertight hatches are closed and sealed properly but not locked, drain holes are free and bilge pumps work.

Local Information

In the USA, storm signals are displayed at U.S. Coast Guard stations, marinas, public piers, and other locations along the coast. The Coast Guard’s standard rough-bar advisory sign is a 6- by 6-foot white diamond-shaped sign with a bright orange border and the words “ROUGH BAR’ in black letters. Two amber lights flash when seas exceed 4 feet in height. Seas may be rough even when lights are not flashing. When rough-bar signs are actively flashing, it indicates deteriorating bar conditions. Tune in to Coast Guard radio to learn of any vessel restrictions that may have been imposed on the regulated boating area of the harbor. Boaters may get more-detailed information on weather conditions and bar conditions from local radio stations, Coast Guard radio, and National Weather Service broadcasts.

Outgoing to Sea

The outgoing vessel must deal with the incoming waves. Do not hit waves at high speed – an airborne vessel is out of control and can cause damage and injury. Do not allow waves to break onto your vessel.  As you leave the harbor or river:

• As you slowly idle towards the breaking waves watch for lulls.
• If a calm spot occurs speed up and run through it.
• If the waves keep rolling in, motor onwards to the breaking waves.
• Gently accelerate over the first section of waves.
• Add power running straight to the next wave, viewing the wave head for the lowest area "the saddle" if you can as this is the last part to break.
• Back off the power just before meeting the next swell.
• Pass slowly through the wave and accelerate again to the next wave.
• Repeat the process until through the area of the waves.

Coming into Harbour or River

Be aware the conditions may have changed since your last observation.  If dangerous, consider alternatives of waiting for conditions to abate which may including waiting for a change of tide or seeking alternative safe harbor.

If at all possible, your vessel should travel at the same speed as the waves. The aim is to travel in on the back of a swell, staying ahead of waves breaking behind the vessel.

• Approach the area of breaking waves and try to pick the spot with the least activity.
• Keep any leads in transit; breakers may obscure your vision of the actual entrance.
• Watch the conditions and choose a set of waves suitable for your entry.
• Position the vessel on the back of a swell and maintain speed, ensuring that:
• Your vessel does not overtake the wave and run down its face.
• Your vessel stays ahead of any wave behind you.
• When the wave ahead of you has broken, accelerate through the white water.
• Beware of steep pressure waves which may be bouncing back off the entrance or shore.
• Adjust engine power and your speed to counter any pressure waves or any outgoing current.

Personal Notes

Though written as an extended metaphor for the river of life and the sea of death, even Alfred Lord Tennyson had something to say about bar crossing. [1]

Sunset and evening star,
And one clear call for me!
And may there be no moaning of the bar,
When I put out to sea,

But such a tide as moving seems asleep,
Too full for sound and foam,
When that which drew from out the boundless deep
Turns again home.

Twilight and evening bell,
And after that the dark!
And may there be no sadness of farewell,
When I embark;

For tho' from out our bourne of Time and Place
The flood may bear me far,
I hope to see my Pilot face to face
When I have crost the bar.

Forum Discussions

External Links

• Crossing a Bar
• Boating Safety
• Crossing the Bar
• Over the Bar at Bahia Del Sol

See Also

References & Publications