actual tide state at 22:51 (BST) on Thursday 25 August 2016
Norfolk Broads real-time Tide Calculator
This Tide clock calculates low water at Gorleston Bar plus 1 hour to estimate LW at Yarmouth Yacht Station. Standard Broads deviations are then applied to calculate the heights at the other locations. Intermediate heights are based on 7 hours of Ebb and 5 hours of Flood, with the 'rule of twelfths' for each applied to give a graphical display of the approximate height at any time. The clock initially displays in realtime. To calculate Broads Tides for any date between 2009 and 2019, click the button to select your desired new date and time. The (24 hour) clock automatically corrects for scheduled BST/GMT. The times shown here (as in all tide tables) are averages for guidance only and are affected by sea, wind & rainfall variations.No responsibility can be taken for any inaccuracies.
| Day 22
|(0.97m tide height at Gorleston)|
(When printing the tide tables, if you would like the row and column background colors to be visible as they are on the screen, in your Internet Explorer, click Tools > Options > Advanced, and then tick the 'print background colors and images' box, (about halfway down the list), then click 'ok'.)
Currents and their Effect
The flow rate at Yarmouth is around 4mph at mid-tide. Even as high as Potter Heigham and Horning, it is still around 1mph. This may not sound very much, but when you consider that the average Broads Authority speed limit is 5mph, (which is measured 'over the ground'), your boat speed through the water would therefore need to be 6mph with an adverse tide, and only 4mph with a favorable tide.
Again, this may not seem worth worrying about, but speed differences as small as this can take a disproportionate amount of effort, (and noise level and fuel consumption) to achieve with the type of boats used on the broads. Without getting too technical, their 'displacement' type hulls are constrained by an absolute maximum possible speed based on their waterline length, irrespective of the size of their engine. Not only that, their fuel and engine efficiency reduces rapidly towards that limit.
A typical 27 foot cruiser requires more than twice the power to achieve 6mph than it needs for 4mph, and with smaller boats the difference is even greater, as their potential maximum speed is disproportionately less.
& Low Tide Time Variations over the System
This Tide Calculator shows the actual height at key points on the system for the date and time displayed, together with the next predicted low and high tide at those points. It initially defaults to now (today, this instant), but you can change the date and time for a new prediction with the buttons provided.
The calculations (as with all Broads tide predictions), are reasonably accurate as regards high and low water times, but the amount of rise and fall is greatly affected by wind and rain conditions. If you are planning to pass under a low bridge, such as Potter Heigham through to Hickling, you cannot always presume that 'low water' will be any lower than 'high water' !!
If there has been high rainfall or if the winds in the North Sea are of any strength and from the North or North east, they tend to push the surface level of the North Sea down to the narrows of the Dover Straits and keep the sea level high at Great Yarmouth. This then has the unfortunate effect of preventing the ebb tide from exiting to the sea, resulting in no low water. Passage through Potter & Wroxham bridges, (for average height cruisers) is frequently blocked for days at a time, particularly in late summer/Autumn.
Therefore, if you planning a holiday cruise in advance to pass under these bridges, you are well advised to leave your plans flexible, and consult the Bridge Pilots nearer the day. (Their use at Potter Heigham is mandatory for hired craft anyway.)
effect of Neaps & Springs
The comparative low water height indicator shows graphically the variations in low water tide height at Gorleston Bar. The 'max', 'average' and 'min' values are based over a three year period of measurement. The figure shown is the actual variance in metres above 'chart datum'. This has no significance within the Broads waterways, but does reasonably reflect the comparative heights between successive low tides.
During 'Springs', (about 3 days after Full or New Moons), the sun and moon exert the most pull on the sea, and we experience both 'higher' high tides and 'lower' low tides than average. During 'Neaps' (around the half moon periods), the sun and moon's gravitational pull are no longer combined, and we then experience less extremes in either, ie the low tides aren't as low, and the high tides aren't as high.
This poses an interesting quandary when considering neaps and springs when planning ahead to pass under low bridges when you know things are tight and you haven't much clearance. During Low Tide Springs, the water level is at it's absolute lowest, so gives the best clearance for safe passage. The subsequent High Water level however, is higher than usual, so you will need to plan for your return approx. 12 hours later to coincide with the next low. If the passage is made however during a Neap period, then you may well have enough clearance at high or low water, as the variation between them will not be so great.