Beach Landings and Tides etc.

[PhilB]

Which are the optimum times for beach landings like Gallipoli? The Med has small tides but, in general, is high tide or low tide better? Is a Spring Tide Preferable to a Neap Tide? Moonlight or cloud cover? Any other meteorological considerations?

Edited 19 August , 2019 by PhilB

[Gareth Davies]

If there are no obstacles below the high water mark then the optimum time would be after the tide has turned and is heading out. This gives the shortest amount of beach to cross by the initial wave and then gives space for the next waves and support.  Springs and Neaps are not relevant factors - it's a set amount of beach that will increase in size that one is after.

 

If there are obstacles below the high water mark a lot will depend on what those obstacles are. Some one might want to float over, others one might want to land to seaward of.

[horatio2]

That is a good Army view. - less far to walk.

The Navy view is quite the opposite: low tide so that embedded obstacles can be seen and avoided and a rising tide so that landing craft do not get stranded on the beach on a falling tide and rendered unusable until floated off 6+ hours later.

Little of this applies at Gallipoli with a small tidal range, fewer obstacles and most landings by boats which are easily hauled off.

Outside the GWF remit but the clashing requirements of Army and Navy are well-illustrated by the planning for D Day in 1944. There a rising tide, after a Spring low tide, was the chosen compromise. Factor in air requirements (daylight or a good moon) and the problem is compounded.

The Gallipoli landings provided the background for the far more comprehensive amphibious planning undertaken in WW2 and in the Falklands War., not least the emphasis on proper loading of ships.

[Gareth Davies]

Absolutely an Army view which totally ignores the Navy's thoughts and works on the assumption that there are enough LCs for everyone!

[healdav]

1 hour ago, Gareth Davies said:

Absolutely an Army view which totally ignores the Navy's thoughts and works on the assumption that there are enough LCs for everyone!

And in my experience the Army always assumes that the tide comes in consistently over the 12 hour period. It doesn't. In some places the main tide will come in (or go out) over 1 or 2 hours, then slowly for the rest of the time;in others it's the opposite; and anything in between. You have to look at every beach separately.

It wouldn't have affected Gallipoli, but it sure does where ever there's a tide.

[pjwmacro]

8 hours ago, Gareth Davies said:

Springs and Neaps are not relevant factors - it's a set amount of beach that will increase in size that one is after.

 

Disagree Gareth. Springs and heaps are relevant (maybe not in the Med at Gallipoli) - more beach will be available at low water springs - and less distance to cover to tera firma at HW springs. But the timings available will shorter. (More water to flow in the same period so it moves faster).

[PhilB]

Thanks, gents. What about light? Who is favoured by light or dark?

[jonbem]

15 hours ago, healdav said:

but it sure does where ever there's a tide

And river estuaries can be very speedy, eg. River Kent at Grange over sands/Morecambe Bay, River Severn (and its bore)

[michaeldr]

7 hours ago, PhilB said:

What about light? Who is favoured by light or dark?

 

In the case of Gallipoli, Hamilton wanted to land at night but the navy was against it, citing:

- the difficulties in transferring fully kitted troops from transports to boats in the dark

- finding the beaches in the dark

- the danger presented by uncharted rocks in the dark

However, an equal danger in broad daylight was the vulnerability of the transports to fire from shore artillery

The compromise was to land at dawn or as soon as possible after first light

[As far as I can see the only other consideration was the weather – in the case of Gallipoli, tides did not enter into the question]

Edited 20 August , 2019 by michaeldr

[PhilB]

If you're landing at first light, you've had to find the right beach and negotiated hidden obstacles in the dark? How soon after first light do you reckon the first troops would hit the beach?

[healdav]

5 hours ago, jonbem said:

And river estuaries can be very speedy, eg. River Kent at Grange over sands/Morecambe Bay, River Severn (and its bore)

Quite right.

 

[Gareth Davies]

4 hours ago, PhilB said:

If you're landing at first light, you've had to find the right beach and negotiated hidden obstacles in the dark? How soon after first light do you reckon the first troops would hit the beach?

 

What's the moon state?  Which direction is one landing from and to (from or into the sun)? 

[Guest]

On 19/08/2019 at 15:46, Gareth Davies said:

which totally ignores the Navy's thought

   

    Hmm- I see inter-service co-operation is still a problem.   Gallipoli has its glitches   But the German experience (and expectation in planning)  in the Second World War-vide D-Day-was that the British would always land at high tide and as near to dawn as possible.  With moon. 

     The experience of the Great War varies a little-  the prime aim in a first landing in the Great War was to get infantry ashore- heavier bits of kit up-front is a feature of the Second World War and consequently much affected planning.. The use of the Royal Navy  as,in effect, supporting artillery- as used by Sir Bertram Ramsay-could well be an interesting topic for Gallipoli as a contrast - but,of course, ship-shore comms. were a bit limited in 1915.

    Gallipoli, with it's different landings and phases, is,in effect 2 types of military thinking clashing to the detriment of the PBF.  At first a naval campaign with  soldiers added, latterly an army campaign with the Royal Navy doing the watery stuff. Gallipoli is NOT a triumph for either way of doing things and ,a la Mountbatten and Dieppe, only gets excused  because of "valuable lessons learned"

[gmac101]

If you want a lot of moonlight, then you'll have to expect a large tidal range as spring tides coincide with a new moon and a full moon. Neaps occur at the half moon.

 

Spring tide comes from the German word springer - to jump, a reflection of the large tidal range 

[gmac101]

Just checked, Friday was a new moon and there was a 0.23m high spring tide at Gallipoli - probably not enough to bother the planners too much 

[Lawryleslie]

6 hour tidal flow is calculated in twelfths. 1st hour 1/12, second hour 2/12, 3rd and 4th hours 3/12 each and reducing similarly in 5th and 6th hours. Half the tidal movement takes place in middle 2 hours. This caused problems during the San Carlos beach landings in Falklands War when there was a delay in the assault and landing craft found themselves in deeper water than was envisaged.

[healdav]

20 hours ago, Lawryleslie said:

6 hour tidal flow is calculated in twelfths. 1st hour 1/12, second hour 2/12, 3rd and 4th hours 3/12 each and reducing similarly in 5th and 6th hours. Half the tidal movement takes place in middle 2 hours. This caused problems during the San Carlos beach landings in Falklands War when there was a delay in the assault and landing craft found themselves in deeper water than was envisaged.

It's only calculated like that as a rule of thumb. Few tides come in or go out, like that. As I said before some beaches are covered by water in an hour, and then the water gets deeper over the next five hours. Sometimes the beach is covered in an hour, and in the next hour mos of the water covers it and the next few hours add only  a couple of inches. And vice versa, and every combination. Each beach is different.

[Lawryleslie]

5 hours ago, healdav said:

It's only calculated like that as a rule of thumb. Few tides come in or go out, like that. As I said before some beaches are covered by water in an hour, and then the water gets deeper over the next five hours. Sometimes the beach is covered in an hour, and in the next hour mos of the water covers it and the next few hours add only  a couple of inches. And vice versa, and every combination. Each beach is different.

But water depth has little to do with it if the beach is large and shallow. The 12ths rule applies to water flow not depth, although of course on a steep beach or river estuary water depth will increase dramatically with water flow.

[healdav]

12 hours ago, Lawryleslie said:

But water depth has little to do with it if the beach is large and shallow. The 12ths rule applies to water flow not depth, although of course on a steep beach or river estuary water depth will increase dramatically with water flow.

If a beach is large and shallow, you usually get a it water covered quite quickly, and then gradually deepening. It makes a lot of difference if you want to bring boats in and out.

[BullerTurner]

On 20/08/2019 at 17:13, Gareth Davies said:

What's the moon state?  Which direction is one landing from and to (from or into the sun)? 

Quite.  From a land based defence POV, a backlit target array is a beautiful thing. Shape/silhouette or even shadow all assist in identifying and distinguishing targets.  Same as the sun, where defending east-west or vice verse helps.