Cyclone and Storm Surge - Iczmpwb.org

2.45
It has been mentioned earlier that most of the rivers and creeks in the Sundarban estuary do not
have any head water discharge from the upstream, meaning thereby that there is no substantial
catchment for these channels on the upstream. Thus there is no possibility of the river current
becoming very high due to a high rainfall in the catchment. The only reason why the river currents
may become high is due to a higher influx of tidal water due to a higher rise on the ocean level, which
may be possible with a storm surge activated by a cyclone. The sudden gush of water in such a case
may affect the concave banks of a river more, since the velocities would naturally be higher than the
average river velocity. Further, in a strong bend, the presence of secondary currents (in a plane
across the river flow) may also aid in undercutting the bank toe.
Figure 2-10. Bank failure and retreat due to undercutting of riverbank base by strong river
current
Figure 2-11. Bank failure modes (From Hey et al. 1995)