nineteen years later…. lessons learnt from kantale breach d w r weerakoon former director general...
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Nineteen Years later….
Lessons learnt from Kantale Breach
D W R Weerakoon
Former Director General of Irrigation
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KANTALE IRRIGATION SCHEME
•Constructed early 7th Century
•Restored in 1875 - 37,124 Acft Augmented in 1954 - 87,750 Acft
1965 -110,000 AcftData
Height of Dam - 60’
BTW - 28’-50’
Side Slopes - 1:3 ~ 1:2.5
FSD - 42’
Spillway – Radial Gated 10/(15’WX8’H)
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Kantale Dam Failure (Sunday 20th April 1986)
First information IE/Army /AGA
Warning the Public Police, Railway,CEB,NWS&DB
Efforts to reduce breach flow
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Prior Warning of Failure
Prior Observation of signs of warning – none
Recent Prior inspection (24th Nov,1985)- 65 runnels on D/S bund slope
-No seepage observed at 22’8’’ of water
-Bund overgrown
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Cause(s) of Failure
Failure of the LB sluice barrel
Deterioration of the sluice barrel
Effect of pile driving in close proximity for constructing the
pump house
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Damage Caused
Loss of Human life- Dead bodies found 68- Persons missing 59
No of families affected 2,035
No of persons affected 10,864
Houses damaged-Completely 592
-Partially 628
Crop destroyed-Standing crops 2,502 Ac-Harvested 627 Ac
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Some Issues Related to Kantale Breach
Observation of signs of prior warning ?
Equipped for satisfactory level of observation ?
Periodic Inspection - satisfactory ?
Standing Orders- Available ? Updated ?
Disaster management
Planned ? Awareness ?
Communication methods-satisfactory ?
Authority with the custodian of the reservoir ?
……? ? ? ?
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Post failure Action
Immediate inspection of 11 reservoirs by a team of specialists Hazard Rating of Dams ID Circular on regular inspection- check list & reports – 1986 JuneEstablishment of a dam Safety unit in ID – 1997
Preparation of standing Orders
Dam Safety Project under Mahaweli restructuring Project
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Dams Under ID Responsibility
Total 281Concrete Gravity 01
Earth 280
Large dams 54
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Modes of Embankment Reservoirs Failure
(Statistics– Global)
Overtopping
Internal Erosion
Structurl Insatability
Other
40%
20%
20%
20%
Source: ICOLD
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Issues for the Present & Future
Availability of Specialized Knowledge & Persons?- Prior Observations and capacity for inference ?
- Training needs
Equipment for satisfactory level of observation?
Periodic Inspections/Follow up action ?
Preparation and updating of Standing Orders ?
Preparedness for Disaster management
Communication methods-satisfactory ?
Authority with the custodian of the reservoir ?
Adequacy of funds
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THANK YOU