Cyclone and Storm Surge - Iczmpwb.org

6.8
embankment shall have to be built with the proper sail as is technically necessary, or rather the best
option would be to excavate out the existing embankment, since the material has withstood the test
of time. The distance of retreat has to be according to a possible stable slope, say at least a
minimum of 3 Horizontal : 1 Vertical, as shown in Figure 6-1.
Figure 6 -1. Recommended minimum distance between the riverbank and embankment
6.2.7. Sluice gates
The sluices are constructed with a sliding gate and a flap gate. The sliding gate is necessary to
prevent outflow of water which is useful for the community of the island. For this, the sliding gate can
be and should be in a closed position except at moments excess water needs to be drained. If the
sliding gate is properly constructed and properly operated, it also can prevent the inflow of saline
water during high tide. The flap gate prevents inflow of water when the sliding gate is not closed on
time or is left open.
The sliding gate is a necessity; the flap is a safety precaution which reduces the discharge capacity
significantly. In theory there are two options to increase the discharge capacity of the sluices without
enlarging the diameter of the culverts, which means the construction of a new structure:
• To remove the flap gate and to rely completely on a proper operation of the sliding gates. In
many countries this option has been chosen in cases that the storage capacity was relatively
large. In periods of heavy rains when spilling is required during series of low tides and
consequently the sliding gate needs to be opened and closed with every tide an extra gate
keeper needs to be called on duty.
• To reduce the negative effect of the flap gate by reducing the weight that pushes on the jet of
water leaving the culvert and which diminishes the discharge capacity of the sluice. This can
be achieved by re-construction of the flap gate structure is such a way that a counter weight