Cyclone and Storm Surge - Iczmpwb.org

6.11
(b) Medium rivers to armour the riverside slope (3:1) of embankments by providing 20 cm thick
dry brick pitching over a layer of 10.0 cm to 12.5 cm thick jhama khoa filter with provision of brick
sausage toe wall.
(c) Embankments facing Bay of Bengal to armour riverside slope (5:1) by providing (2.0 m x 1.0
m x 0.3 m) C.C. Block over 15 cm thick layer of jhama khoa filter with provision of brick sausage toe
wall.
Data
(a) For Embankments along Major & Medium Rivers
(i) Average Ground Level = R.L. 2.00 m (GTS)
(ii) Highest High Tide Level = R.L. 4.50 m (GTS) (considering flood season of 1976)
(iii) Average High Tide Level = R.L. 3.80 m (GTS) to 3.00 m (GTS)
(iv) Lowest Low Tide Level = R.L. (-) 1.80 m (GTS) to (-) 1.20 m (GTS)
(b) For Embankments facing Bay of Bengal
(i) Average Ground Level = R.L. 2.00 m (GTS)
(ii) Highest High Tide Level = R.L. (+) 5.40 m (GTS)
(iii) Average High Tide Level = R.L. (+) 4.50 m (GTS)
(iv) Lowest Low Tide Level = R.L. (-) 2.00 m (GTS)
Crest Level
(a)
For Major & Medium Rivers
From the scheme "Urgent Development Works of Sundarban", the height of wave of major rivers has
been taken as 1.60 m. Allowing free board of 0.6 m above wave, the actual free board measured
from H.H.T.L. comes to (1.60 + 0.60) or 2.20 m.
Hence the crest level of the embankment along major rivers = 4.50 m + 2.20 m = 6.70 m
However, for major rivers under Kakdwip Irrigation Division the crest level has been fixed at 7.10 m
(considering the locations of the embankments which are mostly nearer to Bay of Bengal).
The crest level for all the medium rivers has been fixed at 6.40 m (considering the free board above
wave as 0.3 m).
(b)
For Embankments facing Bay of Bengal
As per guidelines of the "National Coastal Area Protection Project" (NCAPP), the height of wave has
been taken as 2.20 m. Allowing free board of 0.60 m above wave, the actual free board measured
from H.H.T.L. comes to (2.20 + 0.60) or 2.80 m.