Part 1

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THE GREAT THAMES BARRAGE

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“Public Works,”

CONDUCTED BY THE EDITOR OF

“The Surveyor and Municipal and County Engineer.”

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It is not necessary to emphasise in any way the fact that something must be done in the tidal Thames to bring the Port of London up to date, and to maintain it as the great inlet of British commerce. What with numerous newspaper articles, magazine reviews, reports of Royal Commissions and others, and a general murmur of complaint from all persons who use the port for their business or the river for traffic purposes, there have recently been abundant evidences that things are not as they should be. Everyone is agreed on this point, but when it comes to the question of a remedy, there agreement ends and confusion begins.

_What is complained of._

And, first, to briefly catalogue the complaints from all sources. They are as follows:—(_a_) Insufficient depth of water in the river for the increasing size and tonnage of steamships. (_b_) Tide-waiting at Gravesend and at the dock entrances, inward and outward. (_c_) Excessive dues. (_d_) Vexatious restrictions owing to conflicting and overlapping authorities in the river. (_e_) Excessive cost of barging, pilotage, and labour in loading and discharging. (_f_) Loss of time at the port. (_g_) Dangerous navigation, due to tides, bends in the river, narrow channel, fogs, and the crowded state of the river. That these complaints are well founded is generally admitted.

_Remedies Proposed._

The Royal Commission on the Port of London, the Board of Trade, as representing the Government, the Thames Conservancy, the dock companies and others recommend the deepening of the river by dredging as a remedy for (_a_), and as a partial remedy for (_b_) and (_f_). As to (_c_) no remedy seems to be proposed by either, but rather an increase of dues, or in lieu thereof a charge upon the rates of London through the London County Council.

Partly to amend (_d_) it is proposed by all the above authorities, except the Thames Conservancy, that a Port Trust should be created to control the river, instead of the present conflicting authorities of the Thames Conservancy, Trinity House, the City Corporation and the Watermen’s Company.

But as to (_e_) there is no suggestion of amendment, nor is it expected that the proposed deepening of the river will materially improve the dangerous navigation (_g_).

_Port of London Bill, 1903._

The Government has sought to give effect to the Report of the Royal Commission on the Port of London in this Bill, which reached the stage of Committee of the whole House, and was then suspended till next Session (1904).

But as there were seventy petitions presented against the Bill, and a large number of amendments stand on the notices for Committee of the whole House, it may justly be concluded that the Bill satisfies no one, and that the attempt of the Government to force it through the House by stifling discussion of most of its vital points in Committee was a flagrant violation of public rights, and will have a disastrous effect on the future settlement of the question.

_Dockisation the True Remedy._

In 1755 Smeaton proposed the dockisation of the River Clyde as a means of providing a sufficient depth of water for the increasing trade of the Port of Glasgow. His plan was rejected, and the Clyde Trustees have since expended £7,430,000 in dredging and improving the river to a low-water depth of 20 ft., and now spend annually a large sum in maintaining this depth.

Thos. Howard proposed the dockisation of the Avon at Avonmouth in 1877 to provide a sufficient depth of water for vessels passing to the Bristol Docks up and down the Avon, there being a rise and fall of tide in the Severn of nearly 40 ft. His proposal was not adopted because the extraordinary range of tide would have left the entrance unapproachable at low water, causing delay in the Severn Channel.

Messrs. L. Murray and W. C. Mylne recommended the dockisation of the River Wear in 1846, but this was not carried out.

The Czar of Russia has recently approved a great dockisation project, consisting of a dam with locks and sluices across the Straits of Kertch, in the Black Sea, to raise the level of the Sea of Azov for the purpose of facilitating navigation to the port of Taganrog and the River Don. The Sea of Azov will then become a fresh-water lake, with an increased depth of water (14½ ft.) and an area of 10,000 square miles. The dam will be nine miles long, and is estimated to cost £5,000,000.

There is, however, no actual instance of the dockisation of a tidal river from which any data can be obtained.

The Thames, moreover, differs entirely from any of the foregoing rivers, and must be considered on its own merits. The map (Fig. 1) shows that it is already dammed and provided with locks at thirty-four places between London and Oxford, the object of these dams being the maintenance of a uniform level of water for navigation and boating purposes, and to prevent the river running dry in the dry season and exposing the muddy foreshores.

But from Teddington Weir to its estuary the Thames is tidal, and there is no obstruction to the tidal flow except the bridges and the half-tide weir at Richmond, which merely holds up sufficient water to cover the foreshores for the advantage of the riparian owners and of boating.

_The Tidal Thames._

To understand clearly the conditions to be dealt with, it is necessary to consider the daily movements of tide, the affluents, the dock and wharf business and the traffic of the river.

The maps (Figs. 2 and 3) show the tidal river and estuary from Teddington to the North Foreland. [Transcriber’s Note: It seems ‘Teddington’ here is an error for either ‘London’ or ‘Southwark’; that’s what the maps show, anyway.]

The river proper—that is, from Teddington to Gravesend—is forty-six miles long, and averages one-third of a mile wide. Its depth at low water varies from 6 ft. at Teddington to 10 ft. at London Bridge and 40 ft. at Gravesend, and the rise of tide at London varies from 17 ft. to 21 ft. and at Gravesend from 15 ft. to 19 ft., the current usually averaging four knots per hour. At London Bridge the Spring tides flow 5 hours and ebb 7½ hours; while at Gravesend they flow 6 hours and ebb 6½ hours.

The river winds about considerably. The straight line distance from Teddington to Gravesend being thirty-three miles, shows that thirteen miles are added to the river in its bends, some of which—as those at Grays, Erith, Blackwall and Limehouse—are short and tortuous.

The longitudinal section (Fig. 4) of the river from Teddington to Gravesend gives graphically all the data necessary for our purpose. Ordnance Datum (O.D.) is the common datum line of the Government maps. Trinity High Water (T.H.W.) is the water datum usually adopted in the river. High and low water, ordinary and Spring tides (H.W.O.T.—L.W.O.T.—H.W.S.T.—L.W.S.T.) are the levels of the respective states of tide in the river at various points. The highest and lowest known tides are also given, as well as the level of the river bottom and the levels of the principal dock entrance sills and of the crowns of the Thames tunnels, showing their depths below the river bottom.

_Tidal Wave._

The curved lines (in various forms of dotting) represent the levels of the surface of water at various states of Spring tides and clearly show the tidal wave which ascends the river and by its momentum and volume raises the high-water level at the upper end several feet above that at Gravesend.

_The Thames Estuary._

From Gravesend to the Nore is an immense triangular area with sandy bottom, muddy foreshores and several deep channels running in the general direction of the Essex coast line, that is, N.E. to the North Sea. The area may be roughly estimated at 120 square miles, and the navigable depth of the principal channels at from 60 ft. to 26 ft. at low water Spring tides.

The volume of the estuary at high water Spring tides may be taken at 2600 million cubic yards, and at low water Spring tides at 1500 million cubic yards, the volumes of the river from Gravesend to Teddington being respectively 180 million and 80 million cubic yards, so that the volume of tidal water entering the river each tide is about 100 million cubic yards.

_Upland Water._

But there is a daily flow over Teddington weir—excluding the water abstracted by the London water companies—varying during the year on the average as follows:—

Cubic yards. Jan. 11,800,000 Feb. 5,300,000 March 4,100,000 April 3,250,000 May 4,720,000 June 2,900,000 July 1,760,000 Aug. 1,590,000 Sept. 1,160,000 Oct. 1,900,000 Nov. 3,530,000 Dec. 8,230,000

Average daily flow, 4,186,000 cubic yards.

Below Teddington, numerous small affluents add to this volume of upland water as follows:—

Cubic yards per day.

The River Lea and Essex streams on the north bank 60,000 Streams in the Kent district 500,000 To this must be added a large quantity of spring water rising in the bed of the river and land drainage—quantity uncertain 1,000,000 Sewage effluents discharged at Crossness and Barking 1,176,000 Storm water overflow from London sewers 580,000 --------- Total upland fresh water daily average 7,502,000

This gives an average volume of 7½ million cubic yards of fresh water descending and mingling with the oscillating tidal water of the river and estuary, which slowly pushes the latter down into the North Sea. Taking the high-water volume in the river as above at 180 million cubic yards, the proportion of fresh water from the upland daily flow is 1/24th, and therefore it will take 24 days to change entirely the water in the tidal river.

Mr. W. P. Birch has shown that the combination of fresh water and sewage which enters the river below Teddington remains in the river, oscillating up and down with the tides for 45 days before it finally gets pushed out into the North Sea.

In this way the discharge of effluents at Crossness and Barking passes up and down in front of London for more than a month, and it becomes apparent that the tidal action keeps the river continually saturated with about 45 days’ soilage. It is no wonder, therefore, that the conditions of colour, smell and turbidity of the river below Teddington are so vile as compared with the Upper Thames, especially as to the above sources of filth must be added the tidal current, which is so rapid that it keeps the mud continually in suspension, washing it up at one time, depositing it at another, but never permanently leaving it except in the places unscoured by the upland water, such as docks, backwaters and places out of the main current. It has been acknowledged by all writers that if the upland water should be stopped the Thames would become a stagnant oscillating ditch, because all filth discharged into it would remain in it permanently.

The docks trap a very large proportion of this mud, and it costs at least £60,000 per annum to clean it out. The mud enters with the locking water and with that pumped to make up the basins.

_Effect of Dockisation on the River._

It is proposed to construct across the river at Gravesend a dam or barrage similar to that across the Nile, containing numerous adjustable sluices, and in addition a series of very large locks, the dam to hold up the river to about Trinity high-water level (see section, Fig. 4).

The immediate effects will be these:—

(_a_) The tides, Neaps and Springs, will be stopped at the dam.

(_b_) The river will be converted into a long lake having numerous affluents, the principal of which will be its natural flow over Teddington Weir.

(_c_) It will have a slow downward current, never reversed, so that all that enters it will pass downwards to the dam.

(_d_) Its level (normally at Trinity high water) can be regulated to any level above low water by the sluices.

(_e_) Within from 25 to 45 days of the closing of the dam the upland water will have pushed over the dam all the oscillating foul water of the tidal river, and thenceforward the water of the lake will be the same as that of the upper river, and any soilage in it must enter it by sewage or land drainage.

(_f_) There will thus be obtained by one work a navigable depth of water varying from 65 ft. at Gravesend to 32 ft. at London Bridge, without dredging or any interference with the river bottom or banks.

But the consequent effects upon the business and usage of the river will be tremendous:—

(_g_) Ships drawing 30 ft. can then proceed to London Bridge at any hour of the day or night, without waiting for tides.

(_h_) Ships of all tonnages and draughts can traverse the river, anchor anywhere, lay alongside any wharf or quay, always remain at one level for loading or unloading (an immense boon to shipowners and wharf wharfingers) and need not lie out in the river or obstruct the free navigation.

(_i_) Dock entrances can be left open, thus saving the cost and time lost in working them. (The London and India Docks Co. estimates the cost of working their entrances at £50,000 per annum.)

(_j_) There will be no mud entering the docks and backwaters, the water in which will freely circulate with the clean river water.

(_k_) Exceptional tides, being stopped at the dam, will not overflow the river banks as now sometimes happens.

(_l_) Reduced cost of towage, barging, repairing river banks, camp-shedding, quays, dredging, management, control and policing of the river.

(_m_) Greatly increased safety of navigation: no grounding, swinging with the tides, collisions due to tidal drift. The tides are responsible for most of these accidents and for many lives lost—casualties which would not occur in a lake.

In addition to these there is a most valuable asset created in the advantage the new conditions open up for—

(_n_) Pleasure traffic, boating and sailing, fishing and the provision of efficient steamboat services, with fixed piers. London will be provided free with a lake of fresh water 45 miles long and from a quarter to half-a-mile wide. It is certain that this will give rise to extensive pleasure boating of all kinds, which will have ample room owing to the removal of all vessels from mid-stream anchorages to the shores.

The illustrations show the present crowded condition of some of the reaches of the river and the clearance that will be effected by a barrage.

_Water Supply of London._

Perhaps the most important advantage created by the barrage will be the permanent supply of water for the increasing demands of the London area.

By the Act of 1903 has been created a Water Board which is empowered to purchase the water companies’ properties and to administer them in the public interest. These companies claim £47,000,000 for their properties. The ratepayers pay them £3,000,000 annually for their water, and the companies pay £30,000 annually for the greater part of the water which they draw from the Thames.

The figures are as follows:—

Gallons per day. From the River Lea 52,500,000 ” wells in the Lea Valley 40,000,000 ” wells in the Kent Co.’s district 27,500,000 ” the River Thames 185,000,000

Total 305,000,000 -----------

So that two-thirds of London’s water supply comes from the Thames; and as the other sources named above cannot be expanded for future requirements, it is evident that for the increasing demands of London either the Thames or some more distant source must be looked to.

The Royal Commission on the water supply of London estimated that in 1941 these requirements will reach 423 million gallons per day, so that at that date 303 million gallons must be obtained from the Thames or elsewhere.

Now if the Thames is dockised, and the tides kept out of the river, it is evident that much less upland water than is now considered necessary will suffice to keep the river lake fresh and clean, because all sewage and effluents entering the river will be carried directly down to Gravesend; there will be no muddy foreshores and no stirring up of the river mud by the tidal scour.

The river will be, in fact, in exactly the same circumstances as most large lakes—that is, a large body of fresh water, having a main inlet of fresh water at one end, many small inlets along its banks, and one main outlet at its lower end at Gravesend. Such lakes abound all over the world: they are the purest of all waters and never become stagnant.

It is proposed, therefore, that the Thames lake should be regarded as a storage reservoir, so far as water supply is concerned. It will contain sufficient for 320 days’ supply, even at the estimated requirements of 1941; for to whatever extent its waters may become contaminated at and below London, these pollutions cannot work back up the river towards Teddington. It follows, therefore, that between Teddington and London water may safely be drawn off for town supplies, or the supply may be taken as now from above Teddington.

An inspection of the table of flow over Teddington Weir on page 3 will show that in the winter and spring enormous quantities of water, above the quantity considered necessary for scouring the river, flow down and are lost.

A minimum flow of 200 million gallons is fixed by law as the amount needed in summer to keep some sort of cleanliness in the lower river; but in January ten times this amount flows away. It is only for a short time in the months of August or September that the natural flow over Teddington Weir—including the water drawn by the water companies—is a little below 423 million gallons daily, and in those months the surplus might be taken from below the weir without affecting the river materially.

If this be objected to, however, there is another remedy available. The Upper Thames may be used as an aqueduct to convey a larger supply, to be derived from neighbouring watersheds or from wells, the water so obtained to be regulated to meet the requirements, enabling a sufficient amount to be run over the weir to keep the lower river in motion at its upper end. Further down, the small but numerous affluents and springs will keep the river in motion, as they are not affected by the Teddington flow, but give a continuous supply to the river. Mr. Topley, the eminent geologist, in his evidence before the London Water Commission, 1892, stated that there are outside the Thames basin large areas from which water could be obtained, such as East Kent, West Suffolk, Norfolk, Hampshire and Wilts.

It is evident that in this way an enormous prospective outlay for a supplementary water supply for London in the near future may be obviated, and that without adding to the existing plant of the water companies the new Water Board may inherit free of cost a future source of supply which will make their purchase of the London Water Companies’ stocks a good investment and a cheap one for the ratepayers.

_Rail and Road Communication at Gravesend._

The possibilities of this scheme are not exhausted, as there remains to be mentioned the opening of railway communication across the river by a tunnel under the dam and of road communication by a roadway over the dam. These are clearly shown in the accompanying Figs. 4, 5 and 6.