andhrare not strongly dependent on Has, usually, 2en$H. The value
ofKis usually 0.5–0.7. Little is gained by increasing nbeyond 4 or 5, or by
decreasingK. A larger number of narrow basins is often cheaper than a
smaller number of broader ones.
11.10 Lifts and inclined planes
If the provision of water for the operation of high-head locks causes major
problems, it is possible to use boat lifts, for the operation of which the water
requirements are almost zero. To overcome very great heads (as much as
100 m) only boat lifts are really feasible. As a rule, boat lifts consist of hori-
zontal water-filled troughs provided at both ends with gates. The troughs of
the boat lifts have a maximum length of about 100 m. Therefore, they are
suitable for the handling of barges and short (11) push trains; major push
trains have to be disconnected. However, because of the great travelling
speed of the trough, the capacity of the boat lifts is relatively high.
According to the direction of motion of the trough, lifts can be either
vertical or inclined. For balancing and moving the boat trough filled with
water vertical lifts use pistons, floats (Fig. 11.16(a)), counterweight bal-
ances (Fig. 11.16(b)), or other special mechanisms.
Inclined boat lifts usually have the boat trough mounted on a special
undercarriage which travels on a track on an inclined plane, either in the
direction of the longitudinal trough axis or normal to it (Fig. 11.17). As a
rule, the trough is counterbalanced by a suspended weight travelling on an
inclined track below the undercarriage of the boat trough. The accelera-
tion of the trough during starting and the deceleration during braking
must be small enough to maintain the variations of the water level in the
trough within permissible limits, in order to reduce the forces in the
mooring ropes of the boat to an acceptable magnitude. To reduce these
forces, part of the water is sometimes let out of the trough before its lifting
to settle the boat at the bottom of the trough and thus stabilize it. Boat
lifts are more sensitive in operation than locks and more prone to damage.
A special type of inclined boat lift is a design developed by J. Aubert;
it consists of an inclined trough with a mobile water-retaining wall (pente
d’eau), forming a water wedge on which the boat floats. The ‘wall’ is moved
by two coupled electric locomotives with the floating boat moored to them.
Difficulties in operation can be caused by the circumferential sealing of the
travelling water-retaining wall. This type of boat lift has been built at
Montech on the Garonne River (Aubert, Chaussin and Cancelloni, 1973).
The first rotating boat lift– the ‘Falkirk wheel’ – was built in 2002 in
Scotland replacing a flight of 19th century locks connecting the Forth and
Clyde (see Section 11.1) and the Union canals. Although the concept of a
rotating lift has been proposed before (in 1902 a rotating drum with two
internal rotating drum-troughs was proposed for the Danube–Oder canal
488 INLAND WATERWAYS
