The waters of the firth are shallow, and a tidal bore occurs periodically.
Dredging has improved the navigable channel of the river, which is tidal to this point and is lined with quays.
Constant use, increased friction (m o r e especially at high speeds), and damage to the rotator will alter an ascertained log error; head or following seas, strong winds, currents and tidal streams also FIG.
The lake is practically tideless, though true tidal pulsations amounting to 3 in.
Under ordinary conditions the sluices are raised to admit boats to pass from the half flood to half ebb, so that the river remains tidal up to Teddington, the next lock.