Today’s discovery: Loch Lomond now experiencing considerable tidal change

All these years it has been assumed that Loch Lomond – with the River Lomond running from the southern end of the loch in to the Clyde at Dumbarton, is not actually a tidal loch.

But today’s edition of The Herald carries a different picture.

It is running an article on Transport Scotland’s plans  – now to be contracted for around £9 million to McLaughlin and Harvey Ltd – to resolve the 30 year old A82 bottleneck at Pulpit Rock by building a viaduct section of the road out in to the loch.

This is accompanied by a little inset diagrammatic showing a steeply climbing section of road – itself a bit of a puzzle since the road along upper Loch Lomondside is pretty flat, carried on a viaduct.

However, the big surprise is that this viaduct section, carrying across water of course, shows that the structure allows for varying levels from High Water, to Mean Water and Low Water – with a considerable differentiation between the high and low levels.

Does this mean that lovely little Luss will need flood defences or was someone at The Herald asleep on watch?

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25 Responses to Today’s discovery: Loch Lomond now experiencing considerable tidal change

  1. The normal range of water level fluctuation over a year in the Loch is 2m. Some of this is natural due to rainfall and snowmelt, and some can be controlled via the Leven barrage, which on its own can account for nearly 1m of range.

    Obviously any road engineering scheme needs to take account of this.  

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    • A battle hardened Viking force used to crossing the Minches sailing to Orkney and Shetlands and crossing the North Sea (!) to Norway suffered a severe setback in September at Largs because of weather damage to vessels.

      None the less Transport Scotland with their deep nautical knowledge decided that that the MV Ali Cat (70gt) and the the MV Argyll Flyer (170gt) would be suitable for providing a frequent year round transport service not for Viking Berserkers but for the General Public comprising from toddlers to OAPs and those attending hospital.

      In doing so they they obviously felt they had superior knowledge to those who put passenger only ferries in place on the Firth of Clyde before only – but several hundred tonnes larger.

      They also felt competent to disregard the previous Public Enquiry which decided that a passenger only vessel larger than either of those currently on the route would be “weather stretched”.

      No real surprise is there that the current AFL service cannot cope with a breeze?

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  2. Newsie, aside of seasonal variations such as dry in winter (?) rains in summer(?) Is it possible also to conclude that Loch Sloy pump storage could also cause fluctations.

    Don’t actually think the tide has got anything to do with it. But what’s your theory on wind blowing the loch level up or down.

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    • newsroom is waiting on teh script telling her what to say arriving post-haste from teh LIEBOOR Party/Unionist Cringe Assoc.
      Only then will newsie spout more drivel

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  3. Apart from the changes in levels caused by rain and melting snow, I am sure the wind will play a part. A strong SE wind will raise the level at the top of the loch, possibly by quite a lot. I have fished Loch Eck from the shore in a howling gale and have seen the water level rise and fall by up to three feet at the bottom end during strong wind gusts. This happens very quickly in the space of a minute or two, much quicker than any tide.

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  4. The Loch Level is a long and complicated issue and so far, only parts of it have been mentioned.

    Loch Sloy ended up too full years ago and they had to drain it into Loch Lomond – flooding many houses in Luss and elsewere round the Loch.

    The amount of rain water that gravitates to the Loch can be quite daunting when you consider the weeks of endless rain we have and we often see the Loch coming up to meet the road just past Aldochlay.

    The River Leven’s weir has to be controlled very tightly at times as the knock on effect when it hits the Clyde and a High Tide, is to see Dumbarton Town Centre, High Street and Glasgow Road flooded and the fields around the Lomondgate development get submerged.

    All the houses in Castlegreen Street had to have their basements filled with concrete years ago to combat the swimming pools that were appearing on a regular basis and the subsequent rot and damage.

    All of these issues have came up before and the losers were those around the Loch, the decision was made that it was better to flood Luss than Dumbarton.

    Sometimes man makes a much bigger mess when he tries to control nature.

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  5. Loch Lomond has a massive catchment from almost Crianlarich in the north to the Campsies in the south east. It has many large rivers like the Falloch, the Fruin and the Endrick flowing into it but also hundreds of smaller burns and streams. This water has only one way out – down the River Leven to the Clyde. When the tide is high, up to Renton near Alexandria, the fresh water cannot get down and so the Loch backs up. A few years ago, between October and February at a time of melting snow, heavy rain and a high tide the loch level rose by eleven feet. There is a control level of 28feet above sea level and if the height at Balloch rises above this the water board has a statutory obligation to open the barrage and permit no impediment to the free natural flow of water. Of late – the past year or two – the barrage has seldom been raised to store water so the increased levels and fluctuating levels in the loch are wholly natural. As I look out of my window now rocks and small islands that are usually clearly visible are completely unseen. In a few days if there is little rain they will re-appear again so News’s tongue in cheek comments about a ‘tide’ in Loch Lomond is not wholly risible and spurious.

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    • Precisely.

      Changes in the level of Loch Lomond are due to quart into pint pot syndrome. If the water cannot get out faster than it gets in then the level rises. If we have increased rainfall, and sudden melting of snow waters then levels rise.

      “Tidal” fluctuations are due to the gravitational forces of the Sun and Moon acting on bodies of water. The Mediterranean is much larger than Loch Lomond but has far smaller tides than we see in coastal waters.

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      • The Mediterranean does have some tidal range, but it is slight compared with other places on earth. Because the Mediterranean is nearly landlocked, with the only major opening to open seas being the Strait of Gibraltar, the Mediterranean at large is not affected by the movement of large volumes of Pacific waters. The tidal range in mid-ocean is about 2 feet in some areas, which may seem strange at first. But in mid-ocean, there is so much water everywhere, that substantial movement of water at a given place is matched by similar movements all around, amounting to a kind of huge cycling shift. The effects of tide are greatest usually near coastlines, where the water moves up against the unmoving land.

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        • There are quite strong currents that flow through the straits of Messina; no doubt there are other places with significant tidal flows.

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  6. I forgot to say: if the entire volume of water in Loch Sloy was released into the Loch Lomond at the one time it would raise the level of water in the Loch by less than one sixteenth of an inch! The generating of power at Loch Sloy has no material effect whatsoever.

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    • Not sure that’s quite right.

      Loch Lomond is 71 million square metres.

      Loch Sloy contains 34 million cubic metres

      So the entire release of Loch Sloy if it were all at once would raise the Loch by approx half a metre.

      Hardly catastrophic, but I think my maths is right???!!!

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        • No, pay more attention in class.

          One is square metres, the other is cubic metres.

          One is area, one is volume. Spread that volume over that area and you get approx half a metre.

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          • Thank you for those calculations there.

            One thing that I feel is being missed, is the point that Loch Lomond, frequently gets full to overflowing on its own. When Loch Sloy needed to be drained, it wasn’t in the middle of a tropical heatwave, but monsoon season and the Loch had already burst its banks in many places.

            If the volume of water in the Loch is already flooding roads and the surrounding land, adding half a meter on top of that can be catastrophic.

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  7. I always thought that the tide was the effect of the moon circuling the earth and the earth spinning and going round the sun, all causing the sea to be drawn back and fore. We have calculated tide tables that give us pretty accurate predictions of what to expect.
    I don’t think there will ever be tide tables for Loch Lomond as it is not tidal, but just a changing level.

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  8. Sam, we are all obliged to make constructive criticism these days.

    Now it was windy last night as you know, and when the wind blows there is a problem with Newsie’ s electrics. It may well be that she is in the dark, but not for the reasons that you suggest.

    Moreover, there a folks on this website who have had to give up active political participation because the Scottish political landscape suffers from a pathological pyschosis manifesting in paranoia and Pavlovian hatred.

    I kid you not, but at least the commentator concluded that FMQ’s was a sanatized Comedy Cut of the real deal that he experienced.

    So. puleease, a bit of decorum if you would in your wild allegations against poor Newsie.

    And the lock levels? Well we’ve had some good theories now, and maybe the level rise and fall is for all of the reasons stated, save for the deliberate flooding of Luss, which clearly would have been the First Minister’s fault.

    And maybe the Weegies are soap dodging again and not drawing as much water. They’re well known for that.

    Ah balance, pure constructive balance.

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  9. dp has clearly got his figures for Loch Sloy and Loch Lomond wrong and needs to go back to his maths tables whereas Jamie Black is much nearer to the truth.

    Loch Sloy has a capacity of 23 million cubic feet (approximately 651,287 cubic metres). Loch Lomond has a capacity of 92,805 million cubic feet (approximately 2,628 million cubic metres).

    Loch Sloy is only about 1 mile long with a maximum width of less than 1/8th of a mile. The maximum depth is 31 feet which is nearer the southern end. The superficial area is about 65 acres of which 73% is covered by less than 10 feet of water.

    Loch Lomond is approximately 21 miles long with a maximum depth of 623 feet (630 or 105 fathoms on the Admiralty chart). The maximum width of Loch Lomond is 5 miles and the mean breadth of the entire loch is approximately 1.25 miles.

    Hope this helps to correct the information above from dp.

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  10. I’m not sure where Councillor Freeman is a Councillor of, but in any case I would refer him to the Argyll and Bute Council Reservoirs Act 1975 Public Register.

    This fascinating document gives the volumes of water in impounded reservoirs….and, look, on page 7, there is Loch Sloy…and there is the number 35,800,000 cubic metres.

    Even an O Level student can work out that 35,800,000 cubic meters spread over 71,000,000 square metres (Loch Lomond area…figures from wikepedia) gives a number close to 0.5 metres.

    To reassure crazy she-bat, this assumes that Loch Sloy is completely emptied, which is unlikely unless the dam bursts, in which case the problems on the A82 are likely to be on a greater scale than the traffic lights at Pulpit Rock

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