Restoration Methodologies and Conservation Strategies

Pallikkaranai drainage swamp is a fresh water swamp adjacent to the Bay of Bengal near Chennai. It is located about 18 km south of Chennai city at latitude 12 o 54'40" and longitude 80 o 14'00".

This swamp is bounded on the East by Old Mahabalipuram road and South B-Canal, on the West by Tambaram - Velachery road, on the North by Velachery Village, on the South by Karanai - Navalur road. This swamp drains an area of 235 sq.km. and the surplus water from the swamp falls into the Bay of Bengal via Oggium Maduvu, B-Canal, Kovalam back waters and Kovalam creek.

The topography of the swamp is in such a way that it always retains some fresh water storage in it, thus forming a very useful and beautiful aquatic ecosystem. This swamp has many flora and fauna. Many aquatic lives like fish, frog, snails and many micro organisms are found here. Many birds feed and breed here. The swamp feeds more than one thousand water buffaloes daily. The Chennai metropolitan development authority (CMDA) planned to divert the swamp area for other urban development purposes on a large scale which included industrial development. The CMDA appointed Mott Mac Donald International (MMI) of U.K to under take a study in the area and to suggest measures to render the area fit for development.

Then in the context of the "Singapore Corridor" which was then under the consideration of Government of Tamil Nadu (GOTN) for development in the swamp area, the CMDA engaged M/S KBN Engineering and Applied Sciences to conduct an EIA of the area in view of the proposed development. Unfortunately the consultants have under estimated the environmental impact and damage to this aquatic ecosystem.

But in the past two decades, the swamp has been encroached upon for other purposes like construction of an Engineering College, Arts College, Hospital, Sewage treatment plant, solid waste disposal, Madras Rapid Transport System (MRTS), NIOT buildings, firewood wholesale market etc. Thus about 30% of the swamp has already been diverted for other purposes.

But from the beginning the Tamil Nadu P.W.D had their own reservations on diverting the swamp area for other purposes, as it would affect the draining capacity of the swamp and cause flooding in the adjacent areas. So P.W.D proposed the formation of a reservoir in the remaining area after delineating the area already encroached. This will prove to be a blessing in disguise if implemented.

This paper gives the hydrology, usefulness, environmental sensitiveness, biological diversity, socio-cultural aspects etc. associated with this aquatic ecosystem. It also explains how far the formation of a reservoir in the swamp would be effective in preserving this aquatic ecosystem.

The Pallikkaranai drainage swamp, a fresh water swamp, 18 km south of Chennai city lies within the Chennai Metropolitan Development Area. The swamp area is about 30 sq.km. The entire area comes under submersion during North East Monsoon. Then the submersion is slowly relieved in the higher elevations and an area of about 20 sq.km. is available for storage after passing off the flood waters in the Oggium Maduvu. The topography of the swamp has a gentle slope from South to North.

This swamp has been identified as an aquatic ecosystem with all the merits. The pond forms a shallow natural lake. The swamp had been functioning as a flood moderator over the past. The swamp is a wetland, like other waterbodies in the near vicinity. Many irrigation tanks lie in the catchment of the swamp. According to Ramsar convention, this swamp qualifies for preservation.

The catchment area of the swamp is 235 sq.km. The runoff enters the swamp from Velacheri in the North and from Kumuli and Sonallur in the South. Due to the presence of a network of man-made micro-level reservoirs/tanks, and surplus channels, there is some degree of regulation of the peak flows. The waters entering the swamp eventually passes through the Oggium Maduvu to reach the Buckingham canal which flows south and enters Kovalam estuary. The Buckingham canal is not capable of draining the flood waters quickly into Kovalam estuary because of inadequate width and slope.

The CMDA, which has the responsibility of preserving the wetlands and waterbodies in the Metropolitan Development area, has no statute to do so in the master plan. Hence, for any urban development, the target is the waterbodies like tanks.

The Pallikkaranai drainage swamp, a vast area of Government land, available free of cost has become the target for urban development by the CMDA. Over the past two decades, the Government of Tamil Nadu has allotted the swamp area for other purposes.

During 1993 the CMDA engaged M/s.Mott Mac Donald International to study and identify the causes of flooding in the city of Chennai, and to suggest remedial measures. This study is called Chennai Metro Flood Relief Stormwater Drainage Master Plan. The CMDA asked MMI to undertake a study of the Pallikkaranai Drainage Area (PDA) and to suggest measures to render the area fit for development. MMI after considering 6 drainage options, recommended the 6th option for implementation.

When the "Singapore Corridor", an industrial park was under the active consideration of the Government of Tamil Nadu (GOTN), the CMDA in 1995 engaged KBN Engineering and Applied Sciences to conduct an EIA of the proposed drainage plan of MMI and also a land use compatibility analysis for the PDA. The KBN recommended setting up of light/medium/service industry in the PDA.

In 1997 GOTN constituted an expert committee to assess the feasibility of the above scheme for funding. Due to the comments by various agencies, NGOs and press on the likely environmental impacts, the CMDA sought the expertise of NEERI for an independent appraisal of the work of both MMI and KBN to arrive at a final decision. NEERI in their final report of July 1999 had suggested two options. It is upto the Government of Tamil Nadu to take a final decision.

Methodology : The methodology involved in this study includes the close observation of the swamp for 15 years, discussion with academia and other interested groups, oral enquiry with local residents around the area, analysis of articles in media and analysis of the various studies conducted by CMDA and the proposal of PWD etc.

The CMDA is not even prepared to accept the existence of an aquatic ecosystem viz Pallikkaranai drainage swamp. It always mentions the swamp as Pallikkaranai Drainage Area (PDA). For the past 20 years the swamp has been the target for development by encroachers, CMDA and other agencies both private and Government. From the very classification of the area as PDA, the intention of CMDA is very clear that it is for developing of the area for urban development.

The CMDA appointed consultant MMI's area of study as about 50 sq.km., including a portion of patta lands in the periphery of the swamp. The peakflow from the catchment to the Oggium Maduvu through the swamp as worked out by MMI for 100 years return period is 519 m 3 /sec. MMI proposed six drainage options and finally recommended the sixth option. This option is based on the proposal of diverting 50% of the total runoff directly to the Kovalam creek by construction of a cutoff drain and interceptor channels in the southern portion of the area.

But the fact is that the cutoff drain will be able to discharge the flood to the sea if and only if the Kovalam creek is open. If it is not so, this proposal will aggravate the flood problem in the southern half. Moreover the excavation of the drain is not in agreement with the natural slope. The excavation of the drain is too costly and involves recurring Operation Maintenance cost for periodical silt clearance of the drains. Above all, this proposal will cause an imbalance in the natural flow pattern and render the swamp dry in a year of scanty rainfall. Comments by NEERI in their review had been the views of the author from the time the proposal was mooted out by MMI.

The EIA by KBN Engineering mainly involved the identification of all potentially significant environmental impacts associated with the MMI preferred drainage scheme. In its findings KBN has stated that the development of the swamp for industrial purpose is most desirable due to

KBN has also suggested setting up of medium, light and service industry in the swamp.

The author is of the view that both the studies by MMI and KBN are biased. Both the studies, keeping in mind the development of the area for industrial purpose had proposed some drainage options without due consideration for preservation of the natural swamp as an aquatic ecosystem. The TOR for the study itself is biased. If the proposal by MMI and KBN are implemented the swamp will automatically vanish and only the man-made drains and industrial complex will be there.

KBN has stated that the Velachery marsh in the North of the swamp is the only wetland, which needs preservation. In fact the Velachery marsh is not a separate waterbody and it is a part and parcel of the swamp, lying in Velachery village limit. The marsh area will be separated from the swamp only by the proposed developments, which includes the formation of a bund in the east-west direction in the north of the proposed area for development.

Already a considerable portion of the swamp had been diverted by GOTN for other purposes as detailed below.

Besides the above, an area of about 19.00 ha has been allotted for solid waste disposal of the Corporation of Chennai. The area of 100 ha is occupied by an Engineering College, an arts College, Tamil Nadu hospitals, Firewood wholesale market, Perungudi sewage treatment plant etc. The unauthorised occupation for residential purpose and area allotted for slum clearance board may be around 100 ha. Thus a total area of about 474 ha. of the swamp has already been allotted/occupied.

On the personal observation of the author and oral enquiry with the people around the swamp, the following will be the environmental impact if the swamp is not preserved.

1. About 1000 water buffaloes which are freely grazing in the pasture land of the swamp will suffer. The stall feeding of these animals will affect the socio-economic conditions of the people growing cattle in the area.

2. In the authors observation about 60 bird species (as per researchers on biodiversity about 106 species) will lose their habitat/feeding areas.

3. Many aquatic fauna like fish, turtle, frog, snakes, snails etc will lose their habitat.

5. Loss of a variety of plants, grass, trees (about 30 species) including many aquatic species like Cyprus, Astracantha longifolia, Eichornea crassipes, Typha ungustata, lilly, Alligator weeds , Ipomoea, Valesnaria, Lemna sp . and 9 other unidentifiable species.

6. Many flora in the area have medicinal value which will vanish if the swamp is not in existence.

After a thorough review of EIA by KBN, NEERI had recommended two development plans for the area.

Even though the author does not fully concur with the views of NEERI, their proposal is sure to mitigate the negative impacts to a considerable degree.

NEERI's first option is to use the southern half of the area for immediate development (about 15 km 2 ) and to use the northern half for developing a lake. The second option is to utilise the southern half as a woody reserved area and northern half for forming a reservoir as proposed by P.W.D. In the second option it also proposes a central drain to drain the southern half into the proposed reservoir. The second option by NEERI can help in preserving the unaffected swamp area as an aquatic ecosystem.

In order to save the swamp and to preserve it as an aquatic ecosystem so as to reap all the benefits of the system, and to use the water for drinking water, Water Resources Organisation of Tamil Nadu P.W.D has been keen in forming a reservoir in the swamp. The capacity of the reservoir at FRL + 8.00 m and by deepening the swamp upto +5.00 m will be 450 M.Cft. The catchment of the reservoir will be 106.66 sq.km. The maximum flood discharge of 340 cumecs (12,000 cusecs) will be discharged through a regulator proposed across Oggium Maduvu below Old Mahabalipuram road. The earth excavated in deepening the swamp will be utilised for forming a bund of 16 km. length for forming the reservoir. The balance earth is proposed to be conveyed upto 3 km. and deposited in available lands near the reservoir and on the banks of B-canal. The estimated cost of the reservoir at 2001-02 rates is Rs.66.00 crores. The sewage from Perungudi STP now let into the swamp will be diverted through pipes by gravity and let into B-canal directly. The reservoir besides recharging the area will provide drinking water to adjacent areas. The reservoir will also attract pisiculture and recreation. The estimate has already been sanctioned.

Fig.2 Schematic Diagram of Proposed Alternative for PDA Development by NEERI (Alternative B)

Conclusions

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The conclusions are drawn from oral interview conducted with 100 persons of the area. The figure in parenthesis is the percentage of people who agreed to the conclusions.

2. Any urban development in the swamp will aggravate the problem of flooding in the periphery of the swamp (70%).

3. Diverting the swamp for urban development will result in adverse impact on environment (55%).

5. All waterbodies must be preserved as they are of multipurpose use for the community (80%).

6. People in the adjacent areas consider the swamp as a monument and asset (20%).

7. The formation of a reservoir in the swamp will be a good source for recharge of aquifer (70%).

8. Proposed reservoir will be useful for pisiculture and recreation (50%) for drinking (40%).

1. Pallikkaranai drainage swamp is a unique freshwater swamp desired by nature for flood moderation, recharge of aquifers, nourishing flora and fauna. This needs preservation.

4. In a growing city, urban development is essential but it should not be at the cost of environment.

5. All the aquatic ecosystems, like natural lake, freshwater swamp, saltwater swamp, estuary, a man-made tank/reservoir, marshy lands etc. need preservation.

3. Project estimate for "Formation of a reservoir in Pallikkaranai swamp" by W.R.O., P.W.D., October 2001.

PWD Technical Education Sub-division III,
Guindy, Chennai – 600 025. India.
Phone: 2351018 – Extn. 203
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