  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. THE RIVER THAMES BELOW BLACKWALL, 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. |
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