• Thursday, July 31, 2014

It is better to be safe than sorry

Dr. Mehedi Ansary, Professor of Civil Engineering from BUET talks to Ahmad Ibrahim of The Daily Star about the probable consequences of a high-intensity earthquake in Dhaka city.

Dr. Mehedi Ansary
Dr. Mehedi Ansary

The Daily Star (TDS): Often times people become complacent about the idea of earthquakes and precautions are not taken. Can you put into perspective what sort of devastation an earthquake of high magnitude may cause in our country?

Mehedi Ansary (MA): The biggest example we can draw in this regard is the Great Indian Earthquake of 1897 which was an 8.7 on the Richter scale. It caused widespread devastation and was felt over 650,000 km2, from Burma to New Delhi. About 1542 people died across the affected area due to that earthquake. At that moment, the population of Dhaka city was about 90,000 and there were about a hundred brick houses in the city. Right now, the population of Dhaka city is above 1.5 crore and there are some 4,00,000 brick houses in the city. To extrapolate, we have estimated that there might be an infrastructure loss of about 25% of the buildings and that 2,00,000 people might die should an earthquake of similar magnitude and intensity strike the country. That is a frightening number and therefore awareness needs to be the order of the day at the moment. Expert opinions vary but there have been estimations that large earthquakes of such magnitude often recur in 100-200 years. An example of awareness can be drawn from the recent earthquakes in Chile and Haiti. The earthquake in Haiti was of 7 magnitude and 300,000 people perished while in Chile there was an earthquake of 8 magnitude and the human loss was 500. The lesson to be learned from these two instances is that of awareness. If we are prepared, we may be able to mitigate the damages.

TDS: What are the pitfalls that can be seen today in Dhaka and its surrounding areas due to a lack of planning for earthquakes?

MA: Firstly, Bangladesh is situated in a hilly area and mountain ranges are formed as a result of tectonic plate collisions therefore we are in a zone where earthquake activity is frequent. There are about 5 fault lines below Bangladesh and an earthquake of a high magnitude and intensity is very much possible. In an earthquake, the most vulnerable houses are the ones made of brick. The engineered houses that are so common today in the capital are less vulnerable in this regard. Yet the problem remains that most of these engineered houses are designed and built by non-engineers who do not apply the required earthquake proofing steps while building a house. At the moment, there might be an economic loss of up to $5 billion and as more and more people move into Dhaka the exposure risk becomes magnified. Another pitfall is the type of soil on which the buildings are constructed and many parts of the city stand on vulnerable soil which can easily damage buildings during earthquakes.

TDS: Which parts of Dhaka are most at risk from earthquakes?

MA: There are parts of Dhaka where the land has been filled up -- areas including Uttara, Rampura and Bashundhara can be examples. Theses are areas where the land has been filled with soil and the landfilling has not been adequate because people often choose profitability over everything else. Constructing buildings in this area without improving the condition of the soil beforehand makes these areas most vulnerable to earthquakes. Even recently the flood flow zones are being filled up to make way for building sites and this is very dangerous. Although these actions are advised against, the land-filling continues unabated by influential people intent on making profits. The government and planning authorities such as Rajuk need to take on a more proactive role to prevent the devastation which we might slip into.

TDS: What are the steps that can be taken by builders to make sure buildings are earthquake resistant?

MA: The first and foremost priority has to be the land on which the building is being constructed. If the building is situated in the areas where the soil has been badly made then the soil has to be improved. No amount of reinforcement can save the building if the soil is faulty. Secondly, the shape of the buildings should be as orthodox as possible and the columns should use extra rods made of durable steel to reinforce the columns. Earthquake proofing requires a bit of money but this money has to be spent in order to make sure that the buildings are earthquake resistant.

TDS: What are the roles of the planning authorities to raise awareness and make us more prepared?

MA: The biggest role here is of the planning authorities. Rajuk must provide builders with a developed map showing the state of the soil in different parts of the city. If the land is faulty, then they must advise the builders to improve the land before starting construction. Next, they must take the steps of reinforcing already existing structures to makes sure there aren't any large infrastructure losses. Yes, reinforcing is expensive but it pales in comparison to the loss that we might suffer. Another important step is regulation. Authorities must regulate the construction of buildings to make sure no one overlooks the rules and to avoid instances such as the Rana Plaza disaster. At the end of the day, it all comes down to planning. It is better to be safe than sorry. And given the sprawling state of the city an earthquake of a high magnitude stands to make us very sorry indeed.

Published: 12:00 am Thursday, June 26, 2014

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