OUR RIDDLE OF THE SANDS
Shortly before the late war a small volume entitled "The Riddle of the
Sands" had a large circulation. It described the adventures of two
friends, who, in a small yacht, spent their summer vacation in
cruising on the Friesland Coast of Germany, and it gave a graphic
account of their discovery of a wonderful network of canals and
waterways which had been made through the sands, connecting the ports
of Emden, Wilhelmshaven and Cuxhaven. Mysterious craft flitted about,
and their own movements were carefully watched. What is this "riddle
of the sands" they asked? The war gave the answer. It was a great
submarine base for an attack upon England.
We in Liverpool have our riddle of the sands, which, although very
different in character, has proved equally elusive. It has defied
scientific solution, the teaching of hydrodynamics, and has from time
to time almost threatened the existence of the port of Liverpool, and
with it the prosperity of our manufacturing districts.
The approaches to the port have not been maintained (although
assisted) by the use of mechanical or scientific means, but by
encouraging the natural forces to do the work necessary to maintain
the deep water entrances clear and serviceable. There are many now
living who remember that the deep water approach to Liverpool was
through the Rock Channel only with three feet of water at low water,
with dangerous and shifting shoals off the Spencer Spit, and the long
lee shore off the West Hoyle Bank. If these conditions had continued
the Liverpool of to-day would not have existed. The development of the
northern deep water approaches is an interesting study. Liverpool has
solved her own "Riddle of the Sands," not by colossal ambitious
engineering schemes which might have been fatal, but by patient
watchfulness of what nature was doing, or trying to do, and
judiciously assisting her efforts. Nature has practically closed the
Rock Channel and the old Victoria Channel, and concentrated her forces
and opened up the Queen's Channel with over 20 feet of water at low
tide in the dredged cut at the Bar, thus making the port open for
ordinary vessels during twelve hours out of the twenty-four, and
making Liverpool the great port she is--the only deep water port on
the West Coast capable of taking such great ships as the "Aquitania"
and "Olympic."
[Illustration: SS. "Aquitania," 1914]
The Riddle of the Sands as it presents itself to us, divides itself
into two portions:--
The sands of the upper estuary;
The sands of the sea channels;
each forming a very interesting and entertaining subject of inquiry.
THE RIDDLE OF THE UPPER ESTUARY
We have an upper estuary of the Mersey formed like a huge bottle with
a narrow neck entrance at Seacombe, through which the tide rushes at
springs at the rate of five or six knots. At Rock Ferry this estuary,
like a fan, spreads out to Widnes, Runcorn, Ellesmere Port, and
Garston. This vast basin is filled by the tidal waters twice in each
day, forming a great lake; at low water we have a vista of sandbanks
and water, very beautiful in their colour and light effects, the
favourite haunt of wildfowl, which in olden time filled the decoys at
Hale and Widnes.
During the Parliamentary Inquiry into the proposal to construct the
Manchester Ship Canal, it was given in evidence that each tide brought
into this bottle-necked estuary 100,000 tons of sand, which was held
by the water in mechanical suspension and deposited on the banks at
slack water, which takes place at the top of high water. The ebb tide
carries this sand out again. About half ebb a process of erosion takes
place. Tidal streams form through the sand banks, and gradually
underpin the sand, which falls into these streams and is carried out
to sea. On a quiet summer evening the process of erosion going on can
be heard at Bromborough, the loud reports caused by the falling sands
being distinctly audible.
This Riddle of the Sands makes quite a fairy tale, so full of
surprises, so wayward and erratic. Craft and even ships which have
disappeared long since suddenly come into view. The coals which fall
overboard when coaling our great liners in the Sloyne creep along the
bottom and pile themselves on to the sandbanks, and form a welcome
supply of fuel to the villagers. Wells of beautiful fresh spring water
bubble up on the shore at Shodwell, and formerly supplied the Runcorn
coasters with water.
At the mouth of the Alt, and also at Hoylake, the low tides expose the
remains of two remarkable primeval forests, from which have been
gathered many tokens of long bygone generations.
There is one thing these sands will not do. They will not obey the
dictates of man unless they conform to their moods and methods.
The original scheme for the construction of the Manchester Ship Canal
proposed to cut a channel through the sands from Runcorn to deep water
at Garston, a distance of about ten miles, protected on either side by
training walls of stone. The Mersey Docks and Harbour Board very
strongly and successfully opposed this part of the scheme, maintaining
that by thus stereotyping the channel, the process of erosion would be
destroyed and the estuary would become permanently silted up with
sand. There would not be a sufficient head of water impounded each
tide to keep the sea channels and approaches to the Mersey scoured and
fit for navigation.
The magnitude of the reservoir of water gathered at high water in the
upper estuary may be gauged by the fact that spring tides rise 30 feet
and neap tides 20 feet, and form the mighty power for scouring the sea
channels. The riddle of how to treat the upper estuary has therefore
been solved by leaving nature severely alone and permitting no
interference.
THE RIDDLE OF THE OUTER ESTUARY
When we come to consider the conditions affecting the outward estuary,
which extends from the Rock Light to the Bar, we have to take into
account not only the scouring power of the ebb tide, and its capacity
as a sand carrier depending upon the force of the current and the
volume of water, but also the action of waves which is very powerful
in preventing the undue accumulation of sand upon our shores and upon
the great sandbanks lying off the entrance to the port.
Standing on the shore at Blundellsands at low tide and during a
westerly gale, I have seen the shore from Hightown to Seaforth a
moving mass of sand, spreading itself over the surface like a sheet.
Placing a stick into the ground, in a few moments a heap of sand would
accumulate on the windward side. These sand storms fill up all the
mouths of the Alt, and pile the sand up in big banks. If there was no
correcting force these sand storms would quickly fill up the shallow
shores and destroy their capacity to impound the tidal water which
assists the scouring power of the main stream; but at high water with
a westerly gale the waves churn up these deposits of sand, and the ebb
tide carries them out to sea. After a westerly gale I have seen the
shores swept of loose sand down to the hard shore beneath, and the
many outlets of the Alt washed clean, and the black marl which forms
their banks exposed. I do not think that this wave action has been
sufficiently considered in selecting the shallow flats on the west
side of the Burbo Bank as the place of deposit for the sand dredged
from the Bar. They are frequently violently disturbed by the action of
the waves, and the sand is carried by the flood tide back again to the
Bar.
There is another action of which we must take notice; every stream
creates an eddy of slack water, or, it may be, a counter current of
much reduced velocity, in a stream heavily charged with sand such as
our tidal streams, and these eddies may create inconvenient deposits
of sand and accretions to the banks which have to be watched.
THE OLD SEA APPROACHES
Having set out the natural forces we have to deal with, we will
proceed to consider their effect upon the outer approaches to the
River Mersey. These approaches twenty-five years ago were very
indifferent. The Bar only carried eight feet of water at low tide, and
practically for vessels of any size Liverpool was a closed port for
eighteen hours out of the twenty-four. By the employment of sand
dredgers, which have removed millions of tons of sand, this difficulty
has been overcome, but in deepening the Bar the Mersey Docks and
Harbour Board have greatly added to the work which the ebb tide has to
do. That work has to be supplemented by the almost continuous use of
sand dredgers, and has been also assisted by the construction of the
Revetment on the Taylor Bank. This has prevented the flood tide
frittering its strength away over the Taylor Bank, and confines and
concentrates the strength of the ebb stream; but still the formation
of inconvenient lumps in the Crosby Channel suggests that the ebb tide
has more than it can do. It has been suggested that by confining this
channel with training walls constructed along the Burbo Bank and the
Crosby shore the power of the ebb tide would be increased. It is,
however, forgotten that the effect of training walls would be to
diminish the volume of water, and therefore its sand-carrying
capacity, and also that training walls along the Lancashire shore
would rob the channel of the large amount of water now impounded at
high water on the shore, which forms a valuable addition to the first
part of the ebb.
The changes in the outer estuary during the past fifty years have been
quite remarkable.
The old sea channel was the Rock Channel striking off to the west at
the Rock Light, and the fairway was marked by two land marks which
were prominent objects upon the Bootle shore; while the Hoylake and
Leasowe Lighthouses indicated the fairway through the Horse Channel.
The Rock Channel has shoaled, and is no longer used. The old Victoria
Channel took its seaward course between the Great and Little Burbo
Banks. This in process of time has shoaled and narrowed, and is no
longer of any service, and the main channel pursues a north-west
direction between the Little Burbo Bank and the Taylor Bank, and
crosses the Bar through the new Queen's Channel.
The Taylor Bank, which now stretches from the Crosby Lightship almost
to the Bar is of recent formation, and takes the place of the Jordan
Flats. The rapid growth of the Taylor Bank no doubt induced the Dock
Board to construct the Revetment, and it has proved an effective
bulwark against the rebound of the stream round Askew Spit, and its
extension to the north seems to be desirable. The strong flood coming
through the Crosby Channel is no doubt mainly accountable for the
erosion which has taken place at Hightown, and which is now taking
place at Hall Road. The latter can be prevented by the erection of a
timber groin to give a south-west direction to the flood stream.
I have made these sands and sand banks a long study. The late Rev.
Nevison Loraine and I explored, in our canoes, every nook and cranny
of the sand banks, and loved to bathe in the pools which formed at low
water on the Burbo Bank; but this long experience of the riddle of the
sands makes me afraid to dogmatise--nature so often rebels and does
the very opposite to what you expect, and the teaching of the past
tells us that she has been a good friend to Liverpool, and had better
be left alone, only helping her, as by the Revetment, to concentrate
her energy in the direction she wishes to go. A step in the same
direction might be taken by closing the channel which has formed
across the Burbo Bank. In my canoeing days this channel was a mere
gutter, but now it is sufficiently large to abstract much water from
the main stream. It has also often occurred to me that the old Formby
Channel might also be diverted. It serves no useful purpose for
navigation, and if the ebb tide which now flows through it could be
turned into the present Formby Channel it would increase the scour;
but experience may have demonstrated that the flood tide demands the
old channel, and if so it has been wisely left open. I think it is
probable that the flood tide making through this old Formby Channel
strikes the main stream of the flood coming through the Crosby Channel
and rebounds on to the Hightown and Hall Road shores, causing the
erosion at these points.
Great credit is due to the Conservators, the Mersey Docks and Harbour
Board, and to Captain Mace, R.N., for the care and wisdom with which
they have watched over the approaches to our port, and to the
successful way they have handled our "Riddle of the Sands."
LIVERPOOL:
LEE AND NIGHTINGALE, PRINTERS, 15, NORTH JOHN STREET
1920.
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Transcriber's note:
Archaic and variable spelling is preserved as printed.
Minor punctuation errors have been corrected.
Hyphenation has been made consistent.
The title page shows a publication date of MIMXX. This appears to be
a typographical error for MCMXX and has been corrected.
The following changes have been made:
Page 69--section title moved to follow italicised note.
Page 83--pervailing amended to prevailing--... old-fashioned
system of cartage still prevailing.
The frontispiece illustration has been moved to follow the title page.
Other illustrations have been moved where necessary so that they are
not in the middle of a paragraph.