Tidal Flows in Cowes Harbour
11 February 2021
(This notice replaces Local Notices to Mariners 61 of 2016 and 06 of 2018 which are hereby cancelled)
Notice is hereby given that the following information on tidal flows in Cowes Harbour is highlighted to all mariners to promote safe navigation within the harbour.
This notice provides the latest observed changes to the tidal system at Mean High Water Springs (4.4m). Tides above MHWS may result in higher tidal flows than predicted. All harbour users should take these tide flows into account when navigating in the harbour. For further information please see the tidal flow modelling videos at https://www.cowesharbourcommission.co.uk/tidal_simulations.
1. Inner Fairway west of the Cowes Breakwater
When the tidal flow at Nos. 1 and 2 fairway buoys is running in a westerly direction, (expected from HW -2hrs to HW +5hrs) a tidal shadow with significantly reduced flow will be experienced immediately west and south of the breakwater in the Inner Fairway. All craft should be aware that as you pass from the westerly going flow into the tidal shadow a turning moment may be induced.
2. Inner Fairway between the Island Sailing Club and the Eastern Channel (Fig 1)
Between approximately HW -2.5hrs and HW, in addition to the tidal shadow west and south of the Cowes Breakwater, vessels transiting the Inner Fairway between the Island Sailing Club and the Eastern Channel will experience a westerly setting tidal flow of up to 2knots which will have a tendency to set vessels down towards the western shore. This cross current splits into two separate flows on the western side of the fairway in between the Island Sailing Club and the Red Jet terminal with a current of up to 1.5knots running along the foreshore in either direction. Please see figure 1 below.
Small craft should be prepared to alter their heading so as not to be set across the fairway when transiting this area and be aware that large commercial vessels may transit this area on the eastern side of the channel (close to the red buoys) to reduce the risk of being set onto the western shore. In any case, all small craft shall avoid impeding the safe passage of commercial shipping and ferries.
All vessels will have a tendency to be set down towards the western shore when within the westerly tidal streams. All mariners are instructed to navigate with particular caution in the vicinity of the harbour entrance and Inner Fairway.
Fig 1: Typical cross current south of the breakwater HW -2hrs at MHWS
This Local Notice to Mariners shall remain in force until further notice.