Crossing Coastal Sandbars

Coastal bars (shallow banks formed by the movement of sand and sediments) build up at the seaward entrance coastal rivers and lakes. They cause waves to become steeper and, in some cases breaking as they approach the bar. There are many bars along the Australian coastline. Even on a good day, conditions on a coastal sand bar can change quickly and without warning. Local knowledge, experience and the right kind of boat are all critical factors when attempting a crossing.

Here are some bar crossing guidelines and general principles.

Preparations

• Only experienced boaters should attempt to cross a coastal bar and, even then, caution should be exercised.
• Observe the wave patterns and conditions prior to crossing. (Walk down to the break wall)
• Learn what you can about the characteristics of the bar you plan to cross from locals or volunteer marine rescue groups.
• Make sure you ask about any leads and beacons that may assist in navigation over the bar.
• Become familiar with a bar by crossing with an experienced operator before attempting a bar crossing by yourself.
• Ensure your boat is seaworthy and is capable of taking some impact from waves. Conditions offshore can be ideal for boating but the conditions on the bar can be dangerous due to swell.
• Do not attempt a bar crossing in heavy swells and strong wind.
• Avoid crossing a bar on a run-out tide when the most dangerous wave conditions usually occur. Be prepared to cancel or delay the crossing.

Prior to crossing

• Check the tides and weather. Obtain a weather report for the time of crossing the bar and a weather forecast of conditions expected on your return.
• File a float plan – let some one know what you are doing and your estimated time of return.
• Watch other vessels make successful crossings.
• Wear polarised sunglasses – they may help you to judge the deepest water and best route.
• Check that everyone on board is wearing a Type 1 lifejacket and is seated prior to crossing.
• Check that windows and hatches, lines and any moveable items are secured.
• Ensure correct trim. For bar crossing your motor must be trimmed all the way down to ensure maximum control of your vessel during the crossing.
• Test all controls – steering, bilge pumps, engines, fuel, filters and radio battery.
• Use your marine radio to log on and off with your local VMR informing them of the name of your vessel, description and how many persons are on board.
• Check the state of the tide (it is safest to cross on an incoming tide).
• Observe water patterns and sets to establish when calmer periods occur. Look for the deepest water of the channel.
• Look for a position marker or lead so the entrance can be located on the return trip.

The skill of crossing a bar is to know the best water by judging the wave pattern, crossing at the calmest point and manoeuvring the boat around breaking waves. Look for the deepest water or channel.Be patient and watch the sets of swells before choosing the best time to go. Once committed, keep going attempting to turn around in front of an incoming wave can be disastrous. Do not hit the waves at high speed; take them as close to head on as possible. Some bars have waves breaking across the whole entrance and finding a way through may be practically impossible. Be prepared to take a wave head on and take water over the bow if you find yourself in a position where there is no alternative. The boat must match the energy of each incoming wave by maintaining a speed that will lift the bow over the wave, and reducing the likelihood of the wave breaking over the bow and into the boat.

General principles for completing a bar crossings include:

1. Idling towards the breaking waves, looking for lulls, select a line of least wave activity, apply throttle and run through.
2. Keep your boat generally bow-on as the waves approach and do not let the boat turn sideways (broach) to a breaking wave.
3. Head up into the waves and bear away quick on their backs.
4. Accelerate where possible, but avoid getting airborne.
5. Head for the trough of wave (the gap between the waves) between peaking waves about to break.
6. Navigate quickly clear of the bar.
7. Take note of leads and marks to locate the entrance for your return trip.

Coming in from sea

• Lay off from the bar and observe the direction and set of the waves.
• Radio your local VMR and inform them that you are returning to port and are about to cross the bar.
• Locate and identify entrance leads and line your vessel up on these leads prior to commencing your crossing.
• When coming in, high speed boats (at least capable of 18 knots) should travel at the same speed as the waves. The aim is to travel in on the back of a wave, staying ahead of the waves breaking behind the boat.
• Watch for patterns and deeper areas.
• When commencing the approach from sea, increase power to maintain speed within the set of the waves.
• Position the boat on the back of the wave but do not surf down the face of the wave.
• Adjust the boats speed to match the speed of the waves but do not attempt to overtake the waves. Displacement boats may have to come in very slowly to avoid surfing and broaching-to (getting caught side-on to a wave).
• In extreme conditions, the very difficult but vital decision not to come in may have to be made. It may well be safer to stand off in deeper water until conditions improve or to seek alternative shelter.

General advice

1. Never underestimate a coastal bar. Even small waves can capsize or swamp and sink a boat. If you are unsure or inexperienced, why go out and risk lives?
2. Wait until conditions provide a safe crossing that you can handle.
3. Know where the deepest water is and cross during the top of the tide to ensure you don’t risk running aground.
4. Watch for a sufficient time to assess the wave patterns and where waves break the least.
5. Wear life jackets while crossing a bar in any boat at any time. Remember, it is compulsory for everyone on board to wear a life jacket when crossing a designated coastal bar. A capsize can happen quickly and trying to put on a life jacket while in choppy waters is almost impossible.
6. As a skipper, think of your crew and passengers and don’t take risks.
7. Choose your route across the bar carefully and avoid the high standing waves.

Bar Crossing Resource

Roads and Maritime Services (RMS) have a network of web-cams at 15 locations along the NSW coast to assist your preparations. View the Tweed Heads live webcam here.

Although every attempt has been made to ensure the content of this article is correct, the College does not guarantee its accuracy. The article is intended as a guide and does not presume to give advice. The National Boating College accepts no responsibility arising from the use of the information in this article.