(_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.
[Illustration: THE RIVER THAMES BELOW BLACKWALL, As it will appear when
dockised.]
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.
[Illustration: BLACKWALL REACH.]