Cowes Breakwater – Tidal Flows

LOCAL NOTICE TO MARINERS dated No 23 of 2014 refers to Change to Tidal
Flows in Cowes Harbour as result of the continuing construction of the
new Breakwater.

The construction of the Cowes breakwater has reached a level of 3.5
metres above chart datum rising to 5m above chart datum by October 2014.

As predicted prior to construction the breakwater has had an effect on
the tidal flows in the Inner Fairway to the west and south of the
breakwater as follows:

1. Inner Fairway west of the breakwater

When the tidal flow at Nos. 1 and 2 fairway buoys is running in a
westerly direction, (expected from HW -3hrs to HW +3hrs) a tidal shadow
with significantly reduced flow will be experienced immediately west of
the breakwater in the Inner Fairway and extending along the foreshore in
front of the Royal Yacht Squadron.

2. Inner Fairway between the Island Sailing Club and the Small Craft Channel (Fig 1)

Between HW-3hrs and HW vessels transiting the Inner Fairway between the
Island Sailing Club and the Small Craft Channel will experience a
westerly setting tidal flow of up to 1.25 knots which will have a
tendency to set vessels down towards the western shore.

Large vessels entering or leaving the harbour during this period must be
aware that due to the westerly going tide at Nos. 1 and 2 buoys, the
significant reduction in tidal flow in the shadow of the breakwater and
a possible westerly going tide in the Inner Fairway between the Island
Sailing Club and the Small Craft Channel, that when the vessel crosses
the boundaries of these areas the differing tidal flows may induce a
turning moment.

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.

A full set of actual tidal flows will be recorded in November once the
2014 works have been completed and the breakwater reaches its 2014
design height of +5m above chart datum. This data will be published as
soon as it is available.

A large image of the chart and full information is contained at
http://www.cowesharbourcommission.co.uk/Library/LNTM/25_of_2014_Change_to_Tidal_Flows_in_Cowes_Harbour.pdf

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