Geoscience Reference
In-Depth Information
C
A
B
D
Fig. 7.1 Generation of the four different types of abrupt wave by the sudden movement of the sluice gate.
Waves of type A and B are stable positive surges. Waves of type C and D are relatively short lived
(i.e. unstable) negative surges. The dashed lines indicate the original positions prior to the movement
of the gate.
some 67 localities were identified worldwide, where well-defined tidal bores occur, with
reported heights ranging between 0.2 and 6.0 m. Waves of type C are upstream moving
negative surges, which have on occasion been observed in hydropower supply canals,
when the water demand is drastically stepped up. Waves of type D are downstream
moving negative surges, which can result on occasion from a suddenly decreased water
supply in an open channel.
As will be seen below, waves travel faster in deeper water than in shallow water. In the
positive surges of type A and B, which result in a higher water surface, the deeper water
tends to overtake the more shallow leading edge water; therefore, the surge maintains
itself and can be considered stable. In the case of the negative (or receding) surges of
