11. Navigation

Tidal basins are generally outside commercial shipping lanes. But in a few cases, such as the Severn in Great Britain, a lock is required for draughts of over 15 m.

The usual problem is the passage of a very large number of boats with a draught of just a few metres. They can pass through some or all of the channels, above or alongside the water turbines. A relatively inexpensive lock can be placed next to the channel entrance gates to allow passage when the gates are closed, i.e. a third of the time.

Navigation can be enhanced in three ways:

• Many existing harbours in areas of high tidal range are currently inaccessible at low tide; in tidal basins, they are sheltered from storms and sedimentation and their access can be improved efficiently and economically;

• ...