16 Embankments and Their Ecological Impacts
(~) Damage by fracture .
(e) Tilt ing of embankment by
liquefaction of subsoil.
Filter bed_"-",""-.,.,.
(fO em thICK)
(E)
Landwilrd
•
Leil;'~ge Ihroogh infu -conMcling
roofs ilnd pneumafopllores of
mangrows.
(B) Damage by vegetation roots.
~ Brick work
~8r/Ck bats
UMud
PlJ Lalerite
t::z::::..j boulders
~1fr1='~~~*--= C::.. rac =kin9 sclid
\
mud
177
~~~~~~f w~f~r fable
~
;J Li'ltNfied Z~
(0) Cracking of mud due to
liquefoction of subsoil.
Latu41 spruding along
genlle slope
Fig. 16.5. Schematic representation of damages suffered by embankments. a Damage by fracture.
b Damage by roots. c Damage by liquefaction resulting in tilting. d Damage by liquefaction resulting in
cracking of mud base. e Damage by liquefaction resulting in lateral spreading. (Modified from Youd 1984)
lages ofPatherpratirna, Kakdwip and Namkhana as well as the islands of Sagar, Gosaba
and .8asanti (Fig. 16.1) are particularly badly affected by floods almost every year. In
1997 some 5000 people were marooned in the fringe areas of the Sunderbans when a
cyclone hit the coast, causing 6.35-m-high waves to breach the embankments on the
25 August that year.
Wave-induced damage to embankments can be extensive, involving distances varying from one to several kilometres. The force of the water causes the displacement of