River condition and environmental factors are taken into account in deciding in advance whether or not the Regatta should proceed. Here is how this process works:  Stream, Wind, Water Temperature, Land temperature, Precipitation and Water Quality are all in the decision mix.

Stream conditions are generally covered by the Environment Agency’s (EA) Board System for advising river users on safety, which is done for each lock-to-lock reach.  Molesey Regatta is in the Sunbury Lock to Molesey Lock reach.  Stream speed is affected not only by local rainfall but also by rainfall in the upper reaches and catchment areas of the river Thames.  There is no flow gauge on the Molesey reach, but the flow gauge at Walton-on-Thames, just above Sunbury lock, provides a very good indicator for flow speed in the Molesey reach.  In benign conditions the average flow at the Walton gauge is 20 – 30 cu.m/sec.  However, after heavy and continuous rainfall this can rise to as high as 200 cu.m/sec.  Above 100 cu.m/sec at Walton the flow rate in the Molesey reach for a safe and fair competition comes into question, and will be subject to careful review by the committee.

The traditional gauge of flow at Molesey Boat Club is referred to as the “stick test”, where a short floating stick is thrown into the centre of the river and timed between two fixed points about 40m apart .  Experience has shown that if the time taken between the two points is 30 seconds or greater, the flow rate is safe for general rowing.  

See the diagram below for how the committee will respond to EA’s daily publication of navigational safety via this Green/Yellow/Red board system.  

DECISIONMODEL

Wind Speed and Direction will be taken into consideration. Medium-long range weather forecasts will be used to form advance judgements in these cases.  The Regatta Course is along a fairly sheltered stretch of the river, although winds from certain directions are more likely to cause rough waters than from others.  As a guide any predicted or actual wind speed between 11 – 16 knots (Moderate Breeze – Force 4) will require an inspection of the actual conditions, although it is unlikely that this will result in suspension or cancellation.  Above 17 knots (Fresh Breeze – Force 5) there is more likelihood of curtailment but, again, only after a course inspection has been carried out.  

Rainstorms may also be a factor for consideration, although these are more unpredictable and are more likely to have a temporary impact and cause a period of stoppage, rather than cancellation. 

Water Temperature is a potential issue for Winter Head Races, but unlikely to be so for the July Regatta.  When the water temperature falls below 10 degrees C, and particularly if the air temperature is also below 10 degrees C and/or there is a cold wind, additional measures may need to be taken to ensure the safety of rowers, although such conditions may not dictate the cancellation of the event.

Water Quality remains an issue and will be monitored in the days before the regatta.  It is unlikely that poor water quality would be the cause of cancellation, but in the event that quality warnings are in place, messages would be broadcast to competitors to follow BR guidelines and try not to come into contact with the river water and to wash their skin if they do so.  Any accidental ingestion of poor quality river water would normally require attention from the on-site medical team.