Poole's Four Tides - Benjamin Pond - Longshoreman

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Poole's Four Tides

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every twenty four hours .........

Creel, July 1966
by Benjamin Pond

Tidal Movements at Poole, Dorset.
L.W. to next L.W. (6 a.m. to 6.20 p.m.) Here we see an abnormal high tide, due to low barometric pressure of 29.60.The diagram shows the HALF TIDE, locally known as the 'Second Flood'.


There is no part of the British Isles that has so many advantages and attractions as the district around Poole, at least as far as the angler is concerned. Not only is it possible to fish for almost every species of sea fish, there is also within reasonable distance four of the best rivers, these being the Avon, Stour, Frome and Piddle.
The Bournemouth, Poole area has a summer population of a quarter of a million, yet there is plenty of space for the lone angler who wants sea fishing; Poole Harbour's indented coastline extends to ninety-six miles, and the outer shore from the east of the bay to Swanage is fourteen miles long. In addition to all this the boat angler has both the open sea and many deep channels within the harbour itself.
But here we are concerned with local tides, a phenomenon that is unique in this world, Poole being the sole place where the effects are so pronounced.
Both to the east and west of the harbour the double tide becomes less evident the farther you go, for instance at Southampton Water they experience a 'stand still' of tide for a period of about two hours after the tide has been falling for some time.
But at Poole this second flood, or 'half tide', is of the greatest advantage to anglers and navigators. So many changes in direction of flow means that fish come on the feed more often, or if it runs too hard in one spot you can find fish not far distant.
From 1919 to 1941 I kept a daily record, of tide times and levels, in conjunction with barometric pressure,and other data within the Poole area. In addition I also obtained reports from other stations eastwards. What causes this half tide?
The six hour rise flows up the Channel to Dover where, finding The Straits too narrow, returns at full ebb through The Solent and round the Isle of Wight, meeting the Poole ebb.
Being about three feet higher and much more in volume, it overcornes the local tide as it ebbs, thus causing the second, or half-tide, this additional water flowing into all parts of the large harbour.
There is another strange thing if you compare the behaviour of Spring tides with Neaps. Consider the mid-Spring tide which gives H.T. (G.M.T.) at 9 a.m. - the tide will fall for 2.5 hours, then the half-tide will arrive and rise for roughly one hour, then comes the second (or full ebb), giving L.W. at approximately 3.15 p.m. I have added 15 minutes for lunar tide ratio.
What about neaps? These are the most contrary and variable of all as they never run to expected times in any seven days cycle.
I can only state what a normal tide should do. Suppose H.T. is at 3 p.m.; there will be a first ebb for about two hours, then a slow rise for 75 minutes, then comes the full or real ebb until 9.15 p.m. Here again we have to add 15 minutes for lunar time ratio.
These neaps are so erratic that you cannot estimate what any 12 hour period will produce. The first rise may only come up a few inches, if so, you are able to dig lug almost all day long.
Or it may continue to rise for several hours, then barely fall, then later the second will come and make much higher than the fiist tide. This diversity is all due to barometric pressure, as my records confirm.
The Spring tides will come much higher when the glass is low; instead of the normal 6.5 foot rise it will make up to 8 feet - very useful for launching or beaching your boats. It shows how useful a barometer can be, to boat owners, bait diggers and anglers.
The mouth of Poole Harbour is only 400 yards wide and a huge quantity of water has to flow in and out within short periods. Normal Springs rise 6.5 fieet and Neaps 4.5 feet. At the mouth some Springs run at 6 knots.
On leaving harbour, the Hook Sands lie on the port side and are marked by a row of black conical buoys, extending three miles seaward to the bar, where the tide has a gyratory movement and thus provides variety for the angler. Plaice can be had if one anchors between buoys 7 and 9, and between 9 and 11; nearer into the Hook Sands the bass usually feed.
If you want a lazy day drop anchor opposite The Yards in Studland Bay where the tide flow is steady most of the day; you may find eight species of fish here, The Yards, by the way, consist of three projecting ridges of chalk on the cliff face.


 
 
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