J.C.S. Files

Memorandum by the British Chiefs of Staff

Artificial Harbors for Combined Operations
most secret
C.C.S. 307
The enemy has realized that we can only maintain a large invasion force by using ports and he has, therefore, heavily defended the existing ports and their neighboring beaches from sea and land attack. He has also made arrangements to render them unserviceable if they should be captured.
It is, therefore, of vital importance that we should be able to improvise port facilities at an early date. Supplies could then be maintained during unfavorable weather conditions and before we have been able to capture and recondition ports. The British Chiefs of Staff have appointed a Committee to study the whole problem and to make recommendations as a matter of urgency.
The basic requirements for an improvised port are:
Unloading facilities.
Natural Topographical Features
The best use must be made of natural features such as promontories and shallow banks. A study of the area, however, shows that there is only one position where such natural facilities exist.
Ships Sunk To Form a Breakwater
Ships were used to make breakwaters in the last war, but only in nontidal waters. The objections to this method off the coast of France are:
The large range of tide precludes their use except in very shallow water.
The scour effect of the strong tidal stream may cause the ships to become unstable.
The large number which would be required.
New Scientific Devices1
Bubble Breakwater. In principle this consists of a curtain of air bubbles rising from a submerged pipe. The constant upward flow of bubbles destroys the rotary movement of water particles which is associated with waves, thus damping out the waves. Air compressors are necessary to feed the pipe. This method has been used in Russia and full scale experiment is shortly to be carried out in England by the Admiralty.
Lilo Breakwater. It has been found that a quilted canvas bag, inflated by air at a low pressure and ballasted to float so that the greater portion is below the surface, damps out waves. A model breakwater constructed on these principles has been designed and has given promising results. It is hoped to overcome the practical difficulties of mooring, and full scale trials are being progressed at high priority by the Admiralty.
Unloading Facilities
Methods in Previous Use
The process of beaching L.S.T. and L.C.T. and of drying out coasters and barges can be continued with additional safety within the breakwaters. To save wear and tear and to speed up discharge of cargoes, these methods must be supplemented by other facilities.
Piers and pierheads which are capable of being towed across the Channel have been designed and are being put into production. These piers are capable of being moored so that they will stand up to a strong wind, but unloading under all weather conditions will only be possible when they are placed inside breakwaters. These piers are being designed to enable L.S.T. and L.C.T. to “beach” against semi-submerged pontoons which enable them to discharge over their ramps. Simultaneously the upper deck of L.S.T. can discharge their vehicles direct on to an “upper deck” built on the pierhead.
In the Annexure to Appendix “X” of the Overlord plan (C.O.S. (43) 416 (O)),2 C.O.S.S.A.C. has suggested the construction of specially modified 500 feet pierships, which could be sunk in position and which could be connected to the shore by some form of pontoon equipment or two-way pier. He has also suggested the construction of some form of quay on rocks. These and other suggestions are being examined.
If beaches of slope 1 in 40 or steeper can be found within the breakwater, the construction of unloading hards similar to those used for loading in U.K. will simplify the unloading of L.S.T.
  1. Diagrammatic sections of bubble and Lilo breakwaters which are appended to the source text of C.C.S. 307 are not reproduced here.
  2. Not printed. For a digest of this plan, see ante, p. 488.