Nineteen Years later…. Lessons learnt from Kantale Breach D W R Weerakoon Former Director General of Irrigation

KANTALE IRRIGATION SCHEME Constructed early 7 th Century Restored in ,124 Acft Augmented in ,750 Acft ,000 Acft Data Height of Dam - 60’ BTW- 28 ’ -50 ’ Side Slopes- 1:3 ~ 1:2.5 FSD- 42 ’ Spillway – Radial Gated 10/(15 ’ WX8 ’ H)

Kantale Dam Failure (Sunday 20 th April 1986) First information IE/Army /AGA Warning the Public Police, Railway,CEB,NWS&DB Efforts to reduce breach flow

Prior Warning of Failure Prior Observation of signs of warning – none Recent Prior inspection (24 th Nov,1985) - 65 runnels on D/S bund slope -No seepage observed at 22’8’’ of water -Bund overgrown

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

Damage Caused Loss of Human life - Dead bodies found68 - Persons missing59 No of families affected 2,035 No of persons affected 10,864 Houses damaged - Completely592 -Partially628 Crop destroyed -Standing crops2,502 Ac -Harvested 627 Ac

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 ? ……? ? ? ?

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 June Establishment of a dam Safety unit in ID – 1997 Preparation of standing Orders Dam Safety Project under Mahaweli restructuring Project

Dams Under ID Responsibility Total 281 Concrete Gravity 01 Earth 280 Large dams 54

Modes of Embankment Reservoirs Failure (Statistics– Global) Source: ICOLD

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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