Cyclone and Storm Surge - Iczmpwb.org

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alleviating drainage congestion. The reasons for drainage problems of this system may be
summarized as follows:
• Drainage lockage while High Tide and rising of low water level due to rise of river
bed governing the outfall efficiency in an adverse way.
• The old channel section has nearly remained unchanged n spite of big changes
in drainage load.
• Increase of population density resulting in additional loads.
• Huge change in land-use-pattern
• Drastic reduction in spill areas.
The drainage discharge mainly of the following Boroughs is being served by the SWF channel at
present. Part of Borough IV, Part of Borough V, Part of Borough VI, Part of Borough VII, Part of
Borough VIII, Part of Borough X, Part of Borough XI and Borough XII. During heavy rainfall,
substantial area under the above Boroughs gets waterlogged and duration of inundation lasts for a
long period due to inadequate capacity of the existing drainage system outfalling in SWF channel.
To overcome the severe drainage problem, KEIP has taken up sewage and drainage project mainly
for the added areas of Kolkata to address the drainage inadequacies of the area- specially falling
under Borough VII, XI, and XII by construction of new pumping stations and also by augmentation of
the existing pumping stations. This will result in additional discharge in SWF channel.The 3rd
additional pump house at Chowbhaga and the new pumping station at Borough VII will increase the
present drainage load of SWF channel at Chowbhaga point by 25.51 + 70% of 13.00 (since the
discharge of the ail the pumping stations will not synchronize at the same time) = 34.61 m3/sec. The
resulting afflux will surely affect the Full Drainage Level of the upstream channel, too. The Full
Drainage Level (FDL) of crucial Topsia point 'A' will thus be increased from the already strained
inconvenient level during tidal lockage. Due to increase in FDL, more areas will be waterlogged for
longer duration.
The design discharge of SWF channel before reaching additional pump house complex of
Chowbhaga is 46.44 m3/sec. and the proposed pumped discharge from Borough VII is about 9.1
m3/sec. The total discharge comes to about 46.44 + 9.1 = 55.54 m3/sec. The peak discharge
capacity of SWF channel required before reaching the proposed 3rd additional pump house outfall at
Chowbhaga is 55.54 + 8.45 + 11.34 + 11.34+ 25.51 m3/sec. = 112.18 m3/sec. (the capacity of the
Old Pump House, if. Additional P.S., 2nd. Additional P.H and proposed 3rd.Additional P.M. are 8.45
+ 11.34 + 11.34+ 25.51 m3/sec respectively). The objective of setting up the proposed dumping
stations is to provide relief to its catchment area from water-logging upto the design year 2035. This