A Secure Decentralized Disaster Management Information Network (SDDMIN)
Using Rapidly Deployable Wireless Networking & Mobile Computing
8. As a
result of prolonged absence of non-freshets from upper portion of these
deltaic channels of the block and domination of marine influence, new
islands and bar plains are forming in some areas and eroding the
embankments in many parts of the islands of the block. Removal of
material is generally initiated by the tidal currents flowing through
small creeks. As a result, bank erosion takes place in a piece meal
manner which adds to the processes of lateral shifting of the river
course. This leads to conclude that piece meal mechanism of bank erosion
enhances the process of tidal river or tidal creek migration in addition
to the processes applicable for the shifting of meandering streams
having unidirectional flow. These phenomena resulted in further
meandering and as a whole destructive erosion of the embankments.
9. The margin of all the islands dominated by a medium to low energy
tropical meso-macro- tidal environment. The generally mesotidal coast
(Tidal wave amplitude 2 - 4 m) is macrotidal (Tidal wave amplitude > 4
m) at the funnel mouths of estuaries and big rivers. Tidal wave
amplitude varies between 2 to 5.5 meters.
10. Long shore tidal waves of the Bay of Bengal, coupled with
predominant southwesterly monsoon winds and other easterly
to southerly winds blowing onshore with occasional cyclones affect the
block in the summer and post monsoon months, i.e.,
from March April to September-October.
11. Throughout the year, active tidal ingressions into the wetlands,
lowlands, inlets and estuaries are caused by high tidal range (over 5
12. Residence time of high tide and flow of water during low tide is
about 18-20 hours per day.
13. The maximum wind velocity is 16.7 - 50 Km/hr (April - June) and
minimum wind velocity is 10.7 - 11.8 Km/hr (December - February). The
wind velocity during cyclones often ranges from 80 - 140 Km/hr, in some
cases it crosses 180 Km/hr. 3 to 4 cyclones hit the block each year,
average velocity of which reach about 80 - 120 Km/hr. Empirical records
of cyclones showed that severe cyclone, velocity of which reach 150 -
200 Km/hr., hit the block at every 4 - 5 year.
14. All the margins of the block are affected by storms and associated
phenomenon. Sediment mobilization is also very significant along the
passage of cyclones over the wetlands, offshore and wide funnel shaped
estuaries. Cyclones also initiate large scale littoral drift and lead to
devastating coastal modification.
15. High and
low risk zones are classified on the toposheet with database of latitude
longitudes. Databases for shelters, Government buildings, Pakka houses,
drinking water sources, rural hospitals, market areas etc. has also been