Cyclone and Storm Surge - Iczmpwb.org

3.12
3.9. Drainage scheme of Dr. B.N. Dey
As a result of loss of the Bidyadhari, the only available outfall channel, drainage prospect of Kolkata
became a matter of grave concern. A fresh suitable outfall channel had to be identified in the vicinity
in place of the decrepit Bidyadhari river. The city had grown in the meantime and so the internal
system of collection and conveyance of the drainage became woefully inadequate. Against this
disconcerting backdrop, Dr. Birendra Nath Dey (1891-1963), who later became the Chief Engineer,
Calcutta Corporation (1929-43) drew up a scheme incorporating augmented facilities for internal
drainage, as well as a new outfall channel around 30 Km. farther east in Kultigang, a tidal creek,
which ultimately flows into the Bay of Bengal via the Raimangal estuary.
Kultigang which now constitutes the main outfall of Kolkata's drainage opened up much later than the
Bidyadhari. In fact the former feeders of the Bidyadhari like the Nowi, Sunti and Nonagang, from
North 24-Parganas, changed their allegiance to the Kultigang. The Circular-Beliaghata-Newcut-
Kestopur and Bhangar Kata system emanating and catering to rapidly growing urban
conglomerations join the Kultigang. The SWF and DWF channels of Kolkata Corporation including
the discharge of the Tollygunj-Panchannagram outfalls into the Kultigang at Ghusighata. As
urbanization continues in eastern Kolkata further volume of flow will outfall into Kultigang.
The salient features of the Kulti outfall scheme are as under:
From Topsia lock water is directed by gravity up to Ghushighata through a 34 km long lined channel,
where it discharges into Kultigang through a sluice. This is the dry weather flow (DWF) channel.
From the Palmer Bridge (also often referred to as Palmer bazaar) pumping station there is a 7.47 km
long Town Head Cut (THC) drainage channel leading to the Storm Weather Flow, or SWF, channel.
This channel meets the DWF channel at Bantala where there is a primary sedimentation tank to
partially purify the effluents.
From the Ballygunje pumping station there is a 7.163 km long storm water floe drainage channel,
known as the Suburban Head Cut (SHC) which meets the THC at Bantala and flows as a combined
Storm Water Flow Channel, or SWFC.
The 1.829 km long storm water channel emanating from the Dhapa Lock pumping station meets the
THC at Makalpota. The bottom width of the SWF channel is 36.58m and has a carrying capacity of
76.47 cumec. The DWF channel is concrete lined and has a carrying capacity of 18.97 cumec. The
SHC is 34km long and at Ghushighata, it outfalls into the river Kultigang through two regulators
having 20 and 16 sluice gates, respectively.