THE CONTROL OF RIVERS
261
powers to inspect all premises emitting effluent, and to prosecute
offenders, and this has resulted in a general improvement of the
streams under their control. The Lee Conservancy were granted
similar powers so that the water taken from that river by the
Metropolitan Water Board might be protected from pollution. It
is to be hoped that such control as these authorities have exercised
will become general throughout the country.
NAVIGATION
Many of the English rivers were canalised during the eighteenth
and early nineteenth centuries. Roads were bad; and the provision
of cheap waterborne transport was a great step forward. Such
navigable waterways linked up with the system of canals that
spread through the country. In and adjoining Essex, the Lee up to
Hertford, and Stort up to Bishop's Stortford, were deepened
where necessary, locks were provided to divide the river into a
series of level pounds, and wide bends were by-passed by new cuts.
Similar navigation development took place on the Stour up to
Sudbury, on the Chelmer up to Chelmsford, and on the Beam up
to Hornchurch. Insofar as it could be arranged, the pounds were
made to coincide with the already existing mill heads.
The coming of the railways, and later the development of road
transport, has caused barge traffic to dwindle on all but the main
English canals. The relatively hilly nature of the country necessi-
tates frequent delays at locks, the rate of travel is slow, and except
at places where powerful cranes are provided, much labour has to
be provided for ths loading and unloading of barges; consequently
canals suffer disadvantages these days, as compared with road
transport, largely on the question of flexibility.
The artificial maintenance of a river as a navigation renders it
largely useless as a land drain, since it frequently happens that the
river is embanked at or above the level of adjacent land. Alterna-
tive channels have therefore to be provided to drain such low lands
to points below the next lock downstream, and such provision has
nearly always proved inadequate in wet weather. An independent
flood channel is also needed, to accommodate floods, which may
not only put the navigation itself out of action while they last, but
also cause injury to lands in the valley if they are not able to pass
unhindered. And the canalising of the former river channel makes
this too slow a process. When the Chingford Reservoir was built,
this fact was recognised, and flood relief channels were provided
on either side of the reservoir. A large flood relief channel is now
being made from Edmonton to Stratford on the River Lee, to by-
pass the navigation channel and to ease the flood trouble on that
reach of the river. A start was made this year on the lower reach
of this work.