Cyclone and Storm Surge - Iczmpwb.org

2.22
formed does not pose so much of an acute problem.
Water flows into the Sundarbans during rising tide as long as the water levels in the areas accessible
for the incoming tides, to wit: the rivers and the unprotected lands are lower than sea level. Like-wise
water flows to the sea as long as the water in the system of waterways and unprotected areas is
higher than sea level.
The volume of water that flows into the estuary of a river and on the inundated land is that held
between high water and low water levels. The volume of this layer is usually indicated as the "live
storage" of the system. The "dead storage" is the volume of water that remains in the rivers and
creeks at the end of ebb period.
When water starts flowing in, the volume of water indicated as the dead storage is pushed inwards.
This water will fill in the live storage situated at the land side of the estuary. Fresher water from the
sea mixes with older water from the dead storage, but this process takes only place in a limited zone.
As a result of which, the water at the far end of the system is replaced only very slowly by new water
from the sea. A large portion of water moves oscillates within the rivers, without leaving the estuary.
The larger the dead storage is in comparison with the live storage, the larger the volume that remains
in the system for series of tides. This is of importance for the process of erosion and sedimentation in
the Sundarban.
The shape of the volumes of the creeks, channels and the tidal flats of the Sundarbans, providing the
live and the dead storage is very irregular. These may be thought of as a series of reservoir sections
connected to each other through channels. These channels, of course, also contribute to the storage.
The larger the live storage of any section to be filled through one or more canals, the more water is
flowing in and out through these canals with each tide.
When the live storage is reduced because of sedimentation or because of human interventions like
blocking creeks or building embankments around areas presently inundated, less water needs to flow
to and fro in the river sections feeding this part of the reservoir. When the dead storage of a river is
reduced by sedimentation, the wetted area will also be reduced and consequently the current in
these rivers needs to increase to allow the same volume of water to pass. In general it can be stated
that a reduction of the live storage will reduce the incoming and outgoing volumes and that reduction
of the dead storage increases the velocities.