As we embark on a new year with regained freedom and resolve to engage in more outdoor activities, the growing interest in paddle boarding will undoubtedly appeal to the hardier soul as a cost-effective way of enjoying our waterways. With the growth in popularity, we posted our safety precautions for paddle boarders last August and highlighted some pitfalls and sensible risk mitigation measures with a salutary reminder that the RNLI was called to attend 6,361 paddle boarders, canoers, and kayakers over the past decade.
The UK Marine Accident Investigation Branch (MAIB) recently published its report into the tragic deaths of four paddle boarders from a group of nine enthusiasts on a commercial river tour in Haverfordwest in October 2021 which highlighted shortfalls in experience, training, and qualifications of the organisers, Commerical stand up paddle boarding accident on river weir with loss of 4 lives - GOV.UK (www.gov.uk)
The MAIB is a world leader in maritime accident investigations with a brief that spans the entire marine spectrum from merchant ships and fishing vessels on the high seas, to leisure craft and recreational users of our inland waterways. Their reports always include matters of wider interest than the main topic of their investigation and in this case, sheds considerable insight into the dangers of weirs and cold water immersion. These topics should be essential reading for boarders and swimmers, indeed we would strongly recommend this as compulsory reading for all canal and river users.
We have all gazed at the maelstrom currents which circulate wherever a flow is interrupted by obstacles, such as weirs, which are often marked with warning signs, but there is still considerable activity beneath the surface which can be lethally misunderstood. The UK national water safety forum’s Water Incident Database (WAID) recorded that from 2016-2020 there were 19 deaths at UK weirs. This statistic indicated that the public and river users did not fully appreciate the risks presented by weirs. The Construction Industry Research and Information Association (CIRIA) states that the greatest hazard due to weirs is hydraulic. The recirculating flow at the base of the weir can prevent a floating object such as a person, dog, or canoe from escaping. Hydraulic cycling causes the person or object to be repeatedly dragged underwater at the base of the weir, carried downstream underwater, back to the surface, only to be dragged underwater at the weir tow again, eventually leading to exhaustion and drowning. Archimedes's simple rules of buoyancy are diminished due to the aeration caused by air being introduced into the mix. Put simply, for something to float, the density of the liquid has to be greater than the density of the object. The laws of floatation apply only to pure water. Aerated water from turbulence provides less buoyancy and the struggling swimmer or boater can be caught unaware by the loss of uplift which they would expect from undisturbed water. In the offshore industry, ship masters and boat skippers will avoid water where there are visible leaks from gas pipelines, not only due to explosion risk but to avoid loss of stability, and the Merchant Navy Master Mariner syllabus still includes the perils of navigating in an area of subsea volcanic activity.
To add to the tragedy at Haverfordwest, changes in river levels and water conditions will have an impact on what’s going on at the weir. This can change by the hour and whatever conditions were experienced last time may not be the same next time. The cautious recreational craft user will make a fresh assessment whenever they pass close and the sensible boarders and swimmers should avoid weirs completely. Indeed, the Canal & River Trust Boater’s Handbook probably gives the best advice to paddle boarders, ‘do not pass close to any weir, keep well away’. This might be the best advice we can give on this subject.
Written by Cpt Adrian McCourt