Flood Management
AILA
Flood Management Scheme “Reconstruction, Remodeling and Improvement of embankments in Sundarban and adjoining areas in the districts of North & South 24-Parganas, West Bengal , damaged by severe cyclone AILA” being executed by Irrigation & Waterways Department, Government of West Bengal
Devastation of Severe Cyclone 'AILA' in 2009
Severe cyclone ‘Aila’ hit the coastal parts of West Bengal, particularly in South 24-Parganas and North 24-Parganasat around 14.00 hours on 25th May 2009, with wind speed ranging between 120 to 130 kmph and it continued its devastating journey northwards affecting the districts of North 24-Pargnas, Purba Medinipur, Kolkata, Howrah, Hooghly, Burdwan, Birbhum, Uttar Dinajpur, Dakshin Dinajpur and Darjeeling with gradually weakening intensity. Height of tidal surge of swollen sea, exacerbated by the occurrence of the new moon the day after was observed to be around 3.3 more than the predicted level at Sagar Island. Overtopping of embankments occurred at numerous locations, leading to either total collapse or severe damage. Tidal waves entered into the countryside by overtopping or breaching the embankment and damaged thousands of houses and hutments,, washed away roads and inundated huge areas in Sundarban and adjoining areas in the districts of North & South 24-Parganas. Out of total girdle of about 3122 km lengths of embankment maintained by the Irrigation & Waterways Department, wash out / breaches occurred in about 178 km length and a further 600 km length in numerous stretches suffered severe damage. Unless the reconstruction works are taken up immediately after the monsoon, the entire stretch of 778 km of embankments (either washed away or severely damaged by ‘Aila’) would be susceptible to failure under the possible attack at cyclone in future, even of much lesser magnitude compared to ‘Aila’.
Constitution of task forceby the Government of India
In the aftermath of ‘Aila’, a Task Force on ‘Restoration of Sundarban embankments damaged by the cyclone Aila’ was constituted by the Union Ministry of Water Resources in May 2009.
The Irrigation & Waterways Department submitted a proposal to the Task Force for undertaking reconstruction works of total 778 km length of embankment (178 km washed away or breached and 600 km severely damaged) as short-term measures in its 2nd meeting and thereafter a Flood Management Project has been formulated based generally on the recommendations of the Task Force.
Categorization of works in the Project
Depending on the nature of damage and methodology to be adopted for reconstruction / improvement works, following six categories of execution have been considered.
| Category | Description | Total straight length (in Km) |
| 1A | Reconstruction of washed out sea dykesby local earth to be excavated from country side borrow pit. The sea side slope is proposed to be armound with pre cast brick block to withstand wave action. multiple units of blocks are to be placed in polypropylene (PP) rope gabion to form a heavy module. | 10.20 |
| 1B | Reconstruction of 08 nos of 0.9m dia drainage sluices within the reconstructed embankment to facilited drainage of countryside during monsoon period, into the river system. Total approved cost of the project = 5032.00 crores. | 28.80 |
| 1C | Reconstruction of washed out / breached river embankment at other locations (length in individual stretch generally less than 1 km) by local earth from countryside, along with block pitching on riverside slope. | 137.90 |
| 2A | Reconstruction / improvement of severely damaged sea dyke by local earth from countryside, along with block pitching on seaside slope. | 8.75 |
| 2B | Reconstruction / improvement of severely damaged river embankment by local earth from countryside or other suitable places and with block pitching on countryside slope, along with block pitching on riverside slope. | 477.10 |
| 2C | Reconstruction / improvement of severely damaged river embankment by local earth from countryside or other suitable places but without block pitching on riverside slope. | 115.00 |
| Total | 777.75 | |
| Say | 778.00 Km |
• Apart from armouring of sea/riverside slope by brick block pitching of size 53cm x 53cm x 25cm over a layer of geo-textile filter (Category-1C & 2B), cast-in-situ cement concrete block pitching (1:1.5:3) over conventional brick bats filter (Category-1A) & provision of turfing over jute Geotextile filter has been made for the entire length on the country side slope of embankment.
• Adopting anti erosion measures by dropping porcupine cages in a cluster of three rows into the riverbed from L.W.L. towards bottom, whenever deep channel has come closer to the bank. Next series of rows are to be spaced at 7.5 m apart, for the purpose of functioning as permeable spurs as well as silt arrester.
• Reconstruction of 08 nos of 0.9m dia drainage sluices within the reconstructed embankment to felicitated drainage of countryside during monsoon period, into the river system.
Total approved cost of the project = 5032.00 crores
The scheme has been approved Techno-economically initially by the Ganga Flood Control Commission and also by the Advisory Committee on Irrigation, Flood Control and Multipurpose project of MoWR in their 102nd meeting held on 28.01.2010.
The Investment Clearance was accorded thereon by the Planning Commission, Government of India on 26/07/2010 to the approved cost of Rs.5032.00 Crore.
The project was included under the funding of Flood Management Programme (FMP), a State Sector scheme of Ministry of Water Resources, by the Empowered Committee on FMP in their 6th meeting at an estimated cost 1339.50 crores for the construction of Phase-I portion. As per present Schedule of Rates, approx. 110.00 km of embankment can be completed with this amount including cost towards acquisition of land, under Phase-I.