Cyclone and Storm Surge - Iczmpwb.org
Cyclone and Storm Surge - Iczmpwb.org Cyclone and Storm Surge - Iczmpwb.org
3.26 will lead to significant improvement of environmental quality in the area and also the economic improvement of the community. The design discharge with the parameters given below works out to 86.65 m3/sec. in SWF channel in the reach of down stream of Chowbhaga. (Figures 2a & 3) Bed width - 26.20 m FSD - 3.83 m Hydraulic gradient - 0.00007 Side slope - 1.5 H: IV Rugosity coefficient - 0.025 Design discharge - 86.65 m 3 /sec. The additional discharge to be carried by SWF is 112.18 - 86.65 = 25.53 m 3 /sec., say 25.50 m 3 /sec. Bed width - 50.00 m FSD - 3.55 m Side slope - 1.5 H : 1 V Hydraulic slope - 0.00007 Discharge (calculated) - 141.00 m 3 /sec It is found that the tide lockage period on river Haroagong - Kultigong has increased substantially and average lockage period during peak monsoon when, the river rules high, will be 8.95 hours in 12.25 hours of tide cycle. It means that the tide lockage will be about 18 hours in 24 hours. There are two existing sluices at the outfall of SWF and DWF channels through which the discharge is drained into Haraogong - Kultigong river. These two channels meet before outfall in the river. The discharge in DWF being small in comparison to that of, SWF, the discharge in DWF has been ignored in computation. During tide lockage for about 18 hours in 24 hours, discharge to the river is seriously hampered. This discharge can drain to the river for hardly 6 hours in 24 hours. With heavy discharge in the channel and drainage being stopped during tide lockage, the full drainage level upstream of the sluice starts rising causing water-logging in upper reaches. The lower part of SWF Channel consists of mainly rural and semi-rural area. Owing to pressure of population, rapid urbanization is going to change the nature of the area. Consequent upon the changing of rural and semi-rural into the semi-urban and urban area the drainage load in the channel will increase rapidly. Total drainage discharge at outfall has been increased by 10% beyond the projected year 2035 i.e. 10% of 141 cumec to account for the urbanization = 14.10 m3/sec which will be going to add to the already overloaded SWF Channel.
3.27 Some of the other drainage arteries of the City proper and the added areas viz. Beliaghata-Circular- New Cut Canals, Kestopur-Bhangarkata Khal and Tolly's Nullah, which are discussed below. Circular-Beliaghata Khal Circular canal was originally one of the principal navigational arteries, the pioneer in this process was Mr. Tiretta, the first planning and fixing up the alignment was prepared by him. The proposal was however turned down by Lord Wellesley. Another proposal was submitted by Major Scholch in 1824 but he died in 1826 in Anglo-Burmese War. Excavation of the canal was started in 1829 and according to his proposal was completed in 1833. Chitpore Lock was also set up during this year. The Circular Canal, originally conceived as a navigational channel has no gradient Originating at Chitpore, it bifurcates near Gaznavi Bridge ( near R. G. Kar Hospital ) and terminates at E.M. Bypass, the length of this canal being 8.50 Kms. The eastern and branch is known as New Cut Canal up to VIP Road Bridge. For some time past, the channel has been serving as a drainage channel. The Circular Canal is connected with the Hooghly at Chitpore through an outfall sluice and a navigational lock and with Eastern Drainage Channel near Eastern Metropolitan Bye-Pass. New-Cut - Kestopur-Bhangar Kata Khal Further increase in water traffic initiated excavation of New Cut Canal which was started in 1855-56 and completed in 1856-59. It was also thus excavated as a navigation channel with no gradient. The canal system takes off from Circular Canal about 275 metres south of Belgachia (Gaznavi) Bridge. River Bidyadhari at that time had a minor tributary viz. Central Lake Channel, 91/2 miles (15.30 Kms.) in length which used to outfall into the river at Bamanghata, originating in Dhapa Bill. The Lake Channel was however heavily silted up in 1897 thereby leaving the only means of waterway communication in total disarray between Bamanghata and Dhapa. To provide navigational facilities in these areas, excavation of Kestopur Khal started in 1908-10. It used to take off from Aaratoon Jute Mill and outfalling into Bhangar Kata Khal which was excavated during 1897-98. The Kestopur -Bhangarkata Khal system outfalls into river Kultigong through an outfall system. The lengths of this canal system is about 39 Kms. The canals are presently serving as a drainage channel catering the drainage discharge of Lake Town, Bangur, Dum Dum Park, Salt Lake, Rajarhat, Bhangar and some other rural areas Kestopur Khal forms the northern boundary of the Salt Lake City. The Eastern Drainage channel as stated earlier outfalls into Kestopur Khal. This canal system was provided with navigational facility and was known as a part of "Inner Sundarban Route" and used as a waterway connecting erstwhile East Bengal, now Bangladesh. The navigation through the
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3.26<br />
will lead to significant improvement of environmental quality in the area <strong>and</strong> also the economic<br />
improvement of the community.<br />
The design discharge with the parameters given below works out to 86.65 m3/sec. in SWF channel in<br />
the reach of down stream of Chowbhaga. (Figures 2a & 3)<br />
Bed width - 26.20 m<br />
FSD - 3.83 m<br />
Hydraulic gradient - 0.00007<br />
Side slope - 1.5 H: IV<br />
Rugosity coefficient - 0.025<br />
Design discharge - 86.65 m 3 /sec.<br />
The additional discharge to be carried by SWF is 112.18 - 86.65 = 25.53 m 3 /sec., say 25.50 m 3 /sec.<br />
Bed width - 50.00 m<br />
FSD - 3.55 m<br />
Side slope - 1.5 H : 1 V<br />
Hydraulic slope - 0.00007<br />
Discharge (calculated) - 141.00 m 3 /sec<br />
It is found that the tide lockage period on river Haroagong - Kultigong has increased substantially <strong>and</strong><br />
average lockage period during peak monsoon when, the river rules high, will be 8.95 hours in 12.25<br />
hours of tide cycle. It means that the tide lockage will be about 18 hours in 24 hours.<br />
There are two existing sluices at the outfall of SWF <strong>and</strong> DWF channels through which the discharge<br />
is drained into Haraogong - Kultigong river. These two channels meet before outfall in the river. The<br />
discharge in DWF being small in comparison to that of, SWF, the discharge in DWF has been<br />
ignored in computation. During tide lockage for about 18 hours in 24 hours, discharge to the river is<br />
seriously hampered. This discharge can drain to the river for hardly 6 hours in 24 hours. With heavy<br />
discharge in the channel <strong>and</strong> drainage being stopped during tide lockage, the full drainage level<br />
upstream of the sluice starts rising causing water-logging in upper reaches.<br />
The lower part of SWF Channel consists of mainly rural <strong>and</strong> semi-rural area. Owing to pressure of<br />
population, rapid urbanization is going to change the nature of the area. Consequent upon the<br />
changing of rural <strong>and</strong> semi-rural into the semi-urban <strong>and</strong> urban area the drainage load in the channel<br />
will increase rapidly.<br />
Total drainage discharge at outfall has been increased by 10% beyond the projected year 2035 i.e.<br />
10% of 141 cumec to account for the urbanization = 14.10 m3/sec which will be going to add to the<br />
already overloaded SWF Channel.
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