DAM SAFETY: MULLAPPERIYAR AND ITS IMPLICATIONS

Paper presented at the workshop on 'Kerala and Inter-State River Water Agreements' jointly organised by the Indian Society of Interdisciplinary Studies and the Press Club, Trivandrum on March 23, 1997 at the Press Club Hall in Trivandrum, Kerala, India.

The technical aspects of dam safety is a subject that should be handled by experts. This paper attempts only an overview of the subject and interpretation of the information available on the safety aspects of Mullapperiyar, Idukki, Kulamavu and Cheruthoni dams, the latter three forming the Idukki reservoir of the Idukki Project in Kerala (India). Some of the material I am discussing here was collected during the Comparative Study of Hydroelectric Projects in Canada and India undertaken by me on a media fellowship from the Shastri Indo-Canadian Institute.

Before going into the specifics of the situation at Mullapperiyar, let us examine some of the factors associated with dam safety.
Dam safety depends on five factors:

1. Complete investigations;
2. Adequate design;
3. Quality construction;
4. Appropriate operation, maintenance and supervision;
5. Adequate alarm mechanism and well-adapted emergency action plans.

While the first three factors are taken care of in the design and construction stages of the project, the last two are taken care of in the operation phase.*

1. The probability of failure (or vulnerability) of a dam depends on many factors:
2. Spillway capacity;
3. Seismic resistance;
4. Nature of the foundations (a dam founded on bed rock is less vulnerable);
5. Quality of design (Competence of the design engineers, verification methods);
6. Quality of Construction (Competence of the contractor and the supervision);
7. Monitoring;
8. Maintenance;
9. Human factors (Social conflict, terrorism, war etc.)

The long term safety of a dam is primarily a function of degradation of its materials. In case of concrete dams, degradation can result from swelling on account of alkali reactions in the aggregates, disintegration of surfaces on account of weather, leaching in construction joints on account of poor preparation during construction, leaching of grout injected into the foundation and excessive deformation of the foundation and degradation of an entire concrete poul on account of the variable quality of mixes used.

In the 20th century, around 200 notable dam failures have occurred in the World, killing about 8000 people. It is notable that dam failures do occur in developed countries too. The biggest catastrophe recorded in this century had occurred in Vaiont in Italy in 1963. The accident killed about 2600 people. Another accident of nearer proportions occurred in India in 1979-- about 2000 persons lost their lives when the Machhu II dam gave way. Other dam failures in the country included Ashti in Maharastra (this dam gave way twice-- in 1883 and 1933), Tigra in Madhya Pradesh (1970), Panchat (1961), Kadakwasala (1961), Nanak Sagar (1967) and Chikkahole (1972). The failure of the Malpasset dam in France in 1959 killed 421 persons and the Baffalo Creek dam in USA in 1972 claimed 125 lives.