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The generic tendency in naval history has been that deeper ports are better as they allow larger ships to dock at the port. The importance of deeper water ports increased rapidly in the 19th century when ship designed started to incorporate steel and to build larger draught vessels—this development has, in a way, carried on up to now. There is one instance which I've found where a shallow-water port was desirable (below). Are there other examples of naval bases being deliberately situated in shallow-water harbours post-1801?

The one example I know about involved disregarding Darwin as a potential submarine base in favour of Tjilatjap:

Yet the depth of water could be accounted a disability. One of the reasons (given by the American submarine force commander) for withdrawing the tenders from Darwin to Tjilatjap was that if they were sunk by air attack in Darwin harbour the depth was such that it would not be possible to raise them.
—Hermon, 'Volume I – Royal Australian Navy, 1939–1942'


In general, an example of a shallow port being a limitation:

Catherine the Great had planned a relatively ice-free naval base and port at Baltic Port, now Paldiski, west of Revel, but it had proved too shallow and contemporary technology was not up to dredging it.
—Greenhill, 'The British assault on Finland, 1854-1855'

The definition of "deep" vs "shallow" is a tough one. Modern specifics note that 10m is the lower boundary for "deep". The question's focus is on history, however, and I don't think the same applies. Overall, for the arguments to count there should be contemporary evidence from the decision-makers that describe the relative benefits of the military port with regards to its depth, with depth the primary consideration.

Modernising existing older military establishments also doesn't count. In many cases, countries had to get by with what they had access to and the shallow-water harbours were the only available ones. For example, the development of Wilhelmshaven sees gradual dredging to accommodate the increasing cruisers and battleships in the late 19th and early 20th century. Yet, the Germans didn't have (as far as I know) a deep-water harbour that would have been open to the North Sea.

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  • Just to be clear, you're seeking a naval base that was built where the primary consideration was that it had to be a shallow water port? You're excluding modernising existing shallow water ports and ports that had other strategic advantages but which just happened to be shallow water? – Steve Bird Jul 2 '20 at 19:15
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    Just to add to @BrianZ's comment - one of the reasons for the comparative decline in the Dutch navy by the end of the 18th Century was that their ships were starting to be limited in size by their relatively shallow home waters. – Steve Bird Jul 2 '20 at 19:20
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    @SteveBird: That's difficult. I was looking into the development of Wilhelmshaven as an example and there a relatively shallow port was deepened in the 19th and 20th century to accommodate the new larger battleships (and trading vessels these days). At the same time, there was nowhere else the Germans could have built really so they chose the best place they had. So, yes, modernising existing shallow water ports doesn't match this question. Regarding alternative strategic advantages: that's not the primary aim of this question. – gktscrk Jul 2 '20 at 19:27
  • I would assume (but do not know) that if there is a choice it would be ill advised to do so because war ships are heavy, clumsy, and sometimes want to get out quickly. So, necessity dictates the amount of dredging, as pointed out, but apart from that to my limited knowledge military harbours were/are close to the open waters. 10m aren't available everywhere on the Baltic and North sea and a bit of water beneath the keel is enough ... :-) – user43870 Jul 3 '20 at 11:19
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Not an answer by itself - but an explanation of the trade-off against vessel draught when selecting a harbour.

First, the distinction between a port and a harbour:

  • A port comprises the (always man-made) facilities for loading and unloading both cargo and passengers/crew from a vessel.

  • A harbour comprises the facilities (always at least partially natural though now often enhanced by man) in which vessels can seek haven from inclement weather, be stored awaiting use, and await turn for nearby port facilities.

That said ports, and in particular large ones, are nearly always located in or in very close proximity to harbours, for obvious reasons. So the question really should be phrased as

Were military ports ever deliberately situated in shallow-water harbours post 1801?

However that is clearly the intent of the question - so we will continue.

Now the trade-off; In order to anchor securely a boat must feed out sufficient scope (nautical: The length of cable extended when a ship rides at anchor.) of anchor line (often estimated to be 8 times, or even 10 times in bad weather or waves, the water depth. Here, water depth is the height, at high tide and including maximum expected wave height, of the anchor line hull attachment above the harbour bottom.

In consequence of the greater scope required in a deeper harbour, vessels will also require a greater radius of free movement. In particular this radius of free movement must be clear:

  • of all water that might beach a vessel; and

  • all other vessels also at harbour.

Some mitigations are available as regards minimizing interference with other vessels:

All vessels in any harbour must abide by the anchoring rule for the harbour, namely:

  • one point anchor only; or
    If all vessels use one point anchor only then they will allowing free in roughly the same direction due to tide, wind and wave action, though minimum clearances must still be planned and abided by. All vessels will naturally swing to point into any wind, wave, or tide that is exerting a sideways force on them, minimizing any tendency to pull anchor, so a minimum scope may be used.

  • two point anchor only.
    If all vessels use two point anchoring then they will not swing, and thus will not be able to minimize sideways wind, wave, and tidal action. So vessels may be anchored closer together, but will require additional scope to reduce any tendency to pull anchor in inclement conditions.

An aside: In my Cruise Yachting course many years ago, it was repeatedly emphasized that all vessels arriving in an unregulated harbour must seek guidance from a vessel already at anchor, if there is one, as to the anchor rule in use by that other vessel. Failure to either do so, or abide by the guidance received, would of course invalidate any maritime insurance coverage should an incident occur. Only in the happy instance of there not already being a vessel at anchor may a captain choose which anchor rule to use. If one anchored overnight with one rule, then went for a day sail returning in the evening, always ask again because there might have been complete turn-over and a new rule in place.

Finally, the nature of the harbour bottom itself is likewise a primary consideration. A harbour bottom unable to hold anchors in inclement conditions is a bust - so one might choose a shallower harbour with a good bottom over a slightly deeper one without.

So yes, there definitely is a trade-off where too deep a harbour is disadvantageous. Too deep a harbour will reduce the maximum number of vessels which it can house at any one time in safe anchor. Further, in a harbour of varying depth, there is great value to clustering shallower draught vessels in the shallower water and only deeper draught vessels requiring such in the deeper water.

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  • It is good seamanship e.g. not to bring out two anchors when others sway and there's not enough room for everybody, but not everybody obeys these (comfort). Length of anchor "line" depends (chain, type of anchor, ground), 8-10 times is in most areas impossible and actually regionally forbidden because damage to sea floor. Generally one can anchor everywhere, except where it's otherwise prohibited or in buoyed channels. – user43870 Jul 2 '20 at 20:45
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    Your links don't mention such "musts". Huge merchant ships may have their anchorage areas, especially where traffic is dense (North Sea, Gibraltar, ...). Btw., I have anchored at the Canarian Islands in 50 knots of wind several times, ~30 knots regularly, with ~5 times depth (+/- tide) 8mm chain (14m length sailing boat). – user43870 Jul 2 '20 at 20:55
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    Ok, that relativates it. I first understood you were referring to a law, now it's clear that that's not the case. Btw., i have never seen somebody anchoring here with a "line", poople use chain, stainless steel if they can afford. As ground is regularly 10 or more m away, 10 times depth is impossible anyway, that'll be 3-4,000 bucks and 150kg above the waterline. I had to let go once, 80m of precious chain + anchor. A few days later i returned but it was gone. A fishing crew had their lucky day ... Btw.: you must (your dictus) keep an anchor watch ;-) No sleeping for everybody, I am sorry. – user43870 Jul 2 '20 at 21:20
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    @a_donda: Yes, one also must always keep an anchor watch. – Pieter Geerkens Jul 2 '20 at 21:24
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    The "one anchor per vessel" sounds a lot simpler in theory than it actually is in practice with a pack of diverse vessels. Each has a different underwater shape and will thus be affected different by wind and tide. This effect is extreme in a combination of recreational motor yachts (flat bottom) and sailing yachts (keel to resist sideways forces) but I supposed it is also relevant in a battleship + destroyer scenario. – Manziel Jul 3 '20 at 14:31

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