nineteen years later…. lessons learnt from kantale breach

Nineteen Years later….

Lessons learnt from Kantale Breach

D W R Weerakoon

Former Director General of Irrigation

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)

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

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

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 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

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 JuneEstablishment of a dam Safety unit in ID – 1997

Preparation of standing Orders

Dam Safety Project under Mahaweli restructuring Project

Dams Under ID Responsibility

Total 281Concrete Gravity 01

Earth 280

Large dams 54

Modes of Embankment Reservoirs Failure

(Statistics– Global)

Overtopping

Internal Erosion

Structurl Insatability

Other

40%

20%

20%

20%

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

THANK YOU