Abstract:
The Meghna Estuary system is a very dynamic estuarine and coastal system. The sediment
discharge from the lower Meghna River is the highest and the water discharge is the third
highest among all river systems in the world. The changes in tidal flow direction, channel
topography, the occurrence of new channels, accretion of new lands and abandonment of old
ones are the unique features that exists in the Meghna estuary. These processes trigger
changes in sedimentation and erosion rates which are directly related to the change in
discharge and sediment content and bank line shifting
In this study, Meghna Estuary has been taken as a test case to apply a newly proposed
technique where Hydrographic maps prepared from field level data have been used as a
substitute for Satellite images for studying the morphological changes. This newly applied
technique will be a handy tool in detecting major morphological changes of a river bank
and the estuary.
From Previous Studies it has been revealed that accretion is a dominant process in the
Meghna Estuary. Long term study carried out by EGIS shows that the accretion rate is 9.9
sq. km per year in this region. Recent findings from the Meghna Estuary Study carried out
in the year 2000 have also revealed that the accretion rate has increased to 18.8 sq. km per
year. In this study where a new technique has been applied to identify the morphological
changes, accretion has been found to be the dominant process in the study period of the last
30 years (from 1978 to 2008) with nearly 15.5 sq. km. net area accreted per year. But it
showed a sign of declination in net accretion in the later portion of the study period. It has
been found out that during the period from 1978 to 2002 accretion was a dominant process
but during the period from 2002 to 2008 erosion started to dominate and the net result has
been found to be accretion as dominant in the last 30 years.
Based on the results found from the newly applied method of estimating erosion/accretion
and comparing it with other established studies it can be said that the new technique is
suitable to calculate the morphological changes.
