Lanka away from earthquake zones

By Dhaneshi YATAWARA

Geographically Sri Lanka is away from earthquake zones. Following the 2004 tsunami geologists are hoping to include earthquakes or its after effects in the list of natural disasters in Sri Lanka.

Though an earth tremors was not reported in 2004 many parts of the country felt the tremor including areas like Kandy in the Central hills on April 11. Yet the epicentre of the earthquake was more than 1,600 kilometers away in the Java Sumatra earthquake zone (subduction zone).

The National Building Research Organisation (NBRO) said that it is high time that experiments are done to ascertain the level Sri Lankan buildings could withstand earth tremors. They stressed the importance of considering the withstanding capacity of buildings of possible earth tremors in the future.

"Many houses and large buildings were affected by the tremor though there were no damages reported," said Director General of the NBRO Dr. Asiri Karunawardhana. "This made us to think of another natural disaster that may affect Sri Lanka in the future and the need to experiment on building construction on this new aspect," Dr. Karunawardhana said.

Head of Landslide Studies and Services Division R.M.S. Bandara said that considering the number of natural disasters the country faces, buildings should be able to withstand disasters.

"There should be a proper study of the nature of the disaster to construct houses and buildings in disaster prone areas," Bandara said. According to him making slight deviations from standard construction methods can help to avert damages to life and property. This requires thinking out of the box.

"In the past people who built houses in Ratnapura changed the height of the foundation of the house. They constructed the house on an elevated foundation," he said. The 'pila' of the house was high. They knew the height of floods and built houses accordingly. "Unlike those days now we can build concrete columns to elevate the houses. This would allow the water to pass through without any blockage," he said.

There are no landslide resistance buildings, Bandara said. There are certain areas where we have prohibited construction. These details are available with the local authorities of the area," he explained.

There are ten landslide prone districts such as Ratnapura, Kegalle, Kalutara, Galle, Matara, Hambantota, Nuwara Eliya, Badulla, Kandy, Matale.

"We have observed that many landslides occur in these districts," Bandara said. When construction is planned in these areas, it is necessary to take measures that would ensure the stability of the land and any structure built on it.

If anyone constructing a building or a house in a landslide prone area it should be done in a way that would not trigger a landslide.

When we consider landslides in Sri Lanka mostly it is due to man made reasons. Irresponsible use of land leads to many landslides in the past, Bandara added.

The Disaster Management Ministry has already sent circulars to the local authorities of landslide prone districts to consult the Ministry before approving construction.

If the plan is for one of those constructions restricted locations we do not approve that plan. If not, first we do a study of the proposed plan and then recommend steps need to be taken in stabilizing the land and make suggestions for the architectural design of the building as well. "We first consider whether the construction would trigger a landslide. Certain faulty steps in the construction process could trigger a landslide," he explained. If the weight of the building does not suit the land then it could create a landslide.

"There are certain lands that can be stabilised with certain structural designs. In such cases we guide clients on what kind of changes they should do on the land to stabilise it," he further explained and added that they forward these suggestions in writing to the respective local authorities and it is they who are responsible in ensuring the proper implementation of the recommendations.

Bandara said that Sri Lanka should do more research on types of soil and their characteristics and on building constructions that would withstand tremors. "We need to study to what level does Sri Lanka get tremors and many such information in order to continue this study before setting up guidelines," he added.

He said that structural engineers, architects, geologists should contribute to the study, he added.

NBRO has data and designs for construction plans to withstand floods, cyclones and to mitigate landslide possibilities. But now it will be necessary for us to look in to building plans that would withstand possible earthquakes as well.