Marine Navigation at Alnmouth
Alnmouth is a coastal village on the estuary of the River Aln. The River Aln Boat Club (RABC) manages the moorings in the estuary.
Approaches to Alnmouth
The definitive guide to approaching and leaving Alnmouth by sea, including other navigations from Humber to Rattray Head, is the Royal Northumberland Yacht Club's (RNYC's) publication entitled Sailing Directions which we recommend to Members.
Crossing a Bar
The key feature affecting navigation into and out of the Aln estuary is a river mouth bar.
“A mouth bar is an elevated region of sediment typically found at a river delta ... at the mouth of a river .... Sediment is transported by the river and deposited, mid channel, at the mouth of the river. ... as the river widens at the mouth, the flow slows, and sediment settles out and is deposited. … sediment builds up to eventually create a sand bar that has the potential to extend the entire length of the river mouth and block the flow.“ (Wikipedia)
Bars may cause unusually sudden steep and often breaking seas which can reduce the stability and handling of a vessel. A wave from behind can leave you nose down or stalled (wave buries you). A wave broaching can roll or pick up and throw the boat. Either way you may lose steerage. This can result in a grounding and in significant vessel damage and/or personal injury. Bars can shift in days. For more general information on crossing bars see the New Zealand National Code of Practice for Bar Crossings.
Current State of Alnmouth Channel (July 2021)
After passing Church Hill the river channel turns north and heads nearly 0.5Nm alongside the bar towards Marden Rocks before turning east to the sea. In the past it has run shorter lengths or has run south.
For more up to date information visit the channel at low tide or see the Gallery on this Website.
Rounding the Aln Bar (Members' Hints & Tips)
Boats drawing 1m or less may be able to enter or leave the estuary. Due to the height of the Aln bar (up to 3m above Chart Datum) most boats will not be crossing but following the channel around the bar. If there are waves then they will reduce effective depth and will be across the beam. The tide runs at up to 2kts in the narrow part of the channel.
Aim for 2 hrs either side of HW Springs or 1.5hrs for HW Neaps, preferably on a rising tide.
In marginal conditions avoid the dark.
Check the wind speed and direction from Met Office Inshore Waters forecast. Get wave predictions (height/period/direction) from Met Office Beach Forecasts (use Warkworth).
If leaving the river, look at it from up on the hill, e.g. from Crows Nest Lane – check height of waves and are they breaking?
Ensure vessel stability. Lash loose gear including anchors and fuel containers. Batten down deck openings, hatches and doors. Check cockpit drains are clear and operating. Balance weight distribution. Pump bilges.
Crew awake and dressed with lifejackets. Clip on.
Agree a VHF channel with boats in company. Make a test call.
If in company, have a throwing line and tow rope ready.
Check fuel and vent. Check and warm up engine.
Track your plot on GPS/depth charts (later add waypoints for next time), or follow someone who has them.
Leave a sail up in case of engine failure.
Use the integral fuel tank on an outboard (less chance of air lock).
Unless in convoy, ensure any preceding vessel is clear before proceeding.
Watch for swimmers, personal watercraft, fishermen, etc. Consult fishing boats if nets are present
Unless dead calm, approach at moderate speed. Evaluate before crossing. Wait for a sequence of low waves. If in doubt "STAY OUT". When ready, make haste.
Keep a lookout astern for rogue waves. Steer to take larger waves on the stern quarter. Don't surf the waves.
Keep to the seaward side of channel (optionally windward if strong offshore wind).
Watch your depth.
Use the navigation buoys.
If you lose steerage way, drop anchor to bring the boat head to the waves. Request assistance.
Channels & Hazards
In the River:
Beware submerged concrete wartime defences just off and to the north east of Church Hill - these are usually marked by RABC navigation buoys and are indicated on Navionics charts (see below). The submarine cable indicated on Admiralty charts is no longer marked by poles but still exists and can appear above the surface.The main channel within the estuary is currently to the south - smaller boats may use the north channel nearer to high tide. Withies may be visible marking the channel west of Church Hill. Observe the 4 knot speed limit.
Mooring & Anchoring
Members will use their own moorings or may beach. Inbound visitors are advised to turn to starboard opposite Church Hill and take the northerly channel before anchoring as soon as is convenient.
Navionics Chart Updates
Navionics (a Garmin brand) produce electronic navigation charts for chart plotters and for their Boating app. The same charts are freely available at https://webapp.navionics.com. Like most charts of non-commercial rivers they are not updated regularly for inshore and so the indicated river channel may not be relied on. The RABC intends to provide Navionics with updates in two ways. Firstly, subscribing members already use Community Edits to identify and plot key features such as tank traps, rocks and prominent buildings which have become visible on the public charts. Secondly, we suggest that members and visitors who subscribe to Navionics might connect their depth finders to the SonarChart Live feature which will plot the course and depth of the channel and update public charts as they change.