TIDES: PART 1
BEAULIEU RIVER
Standard port -> PORTSMOUTH
Time Dif_ferences Height Dif_frences (metres)
High Water Low Water MHWS MHWN MLWN MLWS
0000 0600 0500 1100 4.7 3.8 1.9 0.8
1200 1800 1700 2300
STANSORE POINT
-0030 -0010 -0005 -0015 -0.7 -0.5 -0.3 -0.3
Fig 7 Secondary Port adjustments for the entrance to the
Beaulieu River (Stansore Point).
Acknowledgements
I am very grateful to Chris Jones (Head of
Tides, UKHO) for his help with this article.
Copyright
All tide tables and tidal curves adapted
Fig 6 Entrance to the Beaulieu River (Imray chart 2200.9).
from UKHO NP 201-09.
Fig 9 Tide table for
Portsmouth,
22 August 2009.
falling tide.
Our next question is how long do we
have to wait until it rises again above
0.9m?
For this we need to find out the time of
the next high water, which occurs at
0049 UT the following day in Portsmouth.
This translates to become 0119 BST at
Stansore Point after allowing for high
tide coming 30 minutes earlier and for the
Fig 8 Tidal curve for Beaulieu (Stansore Point).
BST correction.
We can then mark the time of this next
water at neaps and springs. we have a tidal curve for Beaulieu to high water on our tidal curve and add in
For Portsmouth, the 0000 and 1200 hand to save additional mental anguish the hours, counting backwards on the left
apply to springs and the 0600 and 1800 later on (Fig 8). For our example it is now hand half of the curve.
apply to neaps. 1700 on 22 August 2009 (springs). We can This tells us that we should be able to
The times of high and low water on now look at the tide tables (Fig 9) and work leave any time after 1925, so we can chill
other days will vary a bit, so we just out the values to plot on the tidal curve out and put the kettle on.
choose the values that are closest on the (Fig 8).
day or interpolate between them.
HW Portsmouth 1237 UT
In our next issue we will take a look
HW Stansore 1237-0030 = 1207 UT = 1307 BST at tidal streams and see how we can
SECONDARY HEIGHTS HW Portsmouth 5.0m handle them to best advantage. ■
If we now look at the offsets for tidal
HW Stansore 5.0-0.7 = 4.3m
height we can see that the offset for Mean
LW Portsmouth 0.5m
High Water Springs (MHWS) is -0.7
LW Stansore 0.5-0.3 = 0.2m
meaning that the height of tide at Stansore We know we need at least 0.9m of
Point will be 0.7m less than at Portsmouth tide to get our 1.8m draught boat safely
ABOUT THE AUTHOR
at MHWS. The adjustments for low water over the 0.9m bar at the entrance to the
and neaps and springs are shown in the Beaulieu, so we can add in the line for
CLIVE LOUGHLIN is a chartered
same way. 0.9m (green) going up to the tidal range
engineer, a recreational sailor
and a regular contributor to
Although it’s possible to check the tidal line and then across to the tidal curve.
Sailing Today. Clive would be
curves for Portsmouth and then modify We can see from the right hand half of
pleased to hear from readers about any
specific results accordingly, it is far easier the curve that the height of tide falls to
technical aspects of sailing that may be of
to use the offsets directly on our tidal 0.9m at about 1730. It is now 1700 and so
particular interest to them.
curve for Portsmouth. If we do this, then we have left it too late to chance it on a Email
clive.loughlin@sailingtoday.co.uk.
September 09 Sailing Today 105
ST149 Seamanship
TIDE_RTG.indd 81 16/7/09 18:09:21
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