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| Sunday, 12 May 2002 |
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Features |  |
| News Business Features Editorial
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When the Earth Slips by Jayanthi Liyanage
On April 29 afternoon, the landslide above Line No. 6 at Sarnia Estate within Soranathota Divisional Secretary's limits in the Badulla District, buried five people and injured six more, reducing two houses to ruins. Fifty more families still live in the affected area. Similar disasters had been reported in previous years from Naketiya - Koslande and Asgangula - Ehaliyagoda. In 1989 June, a single earthslip resulted in 300 deaths. Like many developing countries, Sri Lanka is often prone to hydro-meteorological and related disasters such as cyclones, floods, landslides, storm surge, drought, coastal erosion and epidemics. And landslides are among the few natural hazards that had exerted a drastic impact on our economy and the human settlements over the years. Going by the newly-coined adage that providing relief and rehabilitation after a disaster carries a heavier cost than preventing and mitigating the disaster," it becomes more imperative than ever that we take a deep closer scrutiny into the causes which could trigger landslides in areas where we reside and measure we could resort to, to avert a large-scale calamity.
R.M.S. Bandara, Scientist/Engineering Geologist, National Building Research Organization (NBRO) sees landslides as a possible aftermath of development activities and urbanisation. "In the recent history, construction on hill slopes have been widespread," Bandara says. "One reason is that as our population increases, there is less and less flat land available in non-hilly areas. People are now more decentralised and expanding into hilly areas." Apart from the natural causes for earthslips such as effects of rainfall and the terrain's underlying geological formation, increased development activity figures prominently in man-induced landslides. Haphazard construction of houses and other buildings, with scarce attention to construction aspects and regulations, is one such man-made cause. "In mountainous areas, people cut the hills to construct houses and empty the excavated earth down the slope," Bandara explains. "This leaves a gaping land cut over the house. In Sarnia Estate, the land behind the lines had been cut and left with no tree cover to prevent erosion. Through carelessness, the inhabitants had failed to see the tension cracks appearing on the cut land. Finally, the land came crashing down on them." "When you cut a sloping land, what you take away must be filled. That's where a retaining wall around the house becomes a good safety precaution," he adds. Gem mining is another man-induced cause. Carelessly abandoned quarries often result in unexpected earthslips. Water leaks from irrigation channels could be yet another. Bandara is also very critical of the manner the local property developers construct the drainage system to their properties. Our property developers should plan the drainage paths, diverting drainage away from the land before they divide the property into land blocks for separate houses. But what they usually do is block out the land and plan drainage for each block separately." Which could result in the drainage of one block flowing into another. "In Nawalapitiya, a house had been built after blocking a drainage path flowing from above the land. One day, the whole thing gave way and the land slipped." Always be mindful of any existing drainage system of a land before you design a new system, Bandara cautions. Going on the philosophy that earthslips can be predicted if proper investigation is done in time, NBRO's launched its Landslide Hazard Zonation Mapping Project in 1991 in the wake of catastrophic landslides reported from the island in 1986 and 1988. It identifies major areas in seven districts - Nuwara Eliya, Badulla, Ratnapura, Kegalle, Kandy, Matale and Kalutara, as being landslide prone. Landslide Hazard Zonation Maps for Badulla, Nuwara Eliya, Kegalle and Ratnapura at 1:10,000 and 1:50,000 scales are now complete. NBRO requests town planner and private developers to refer the maps before they embark on any construction or development activity on these areas, to mitigate the likelihood of an earthslip. "We are now mapping Kandy," says Bandara. The Ministry of Lands recently published and requested public comments on its Draft National Land Use Policy. Item 6 of its "No. iii. Land and Nature" states that "only activities that stabilises the soil cover will be permitted on earthslip prone areas; measures will also be taken to reduce the occurrence of earthslips in such areas." The need is still there for a more comprehensively spelled out and imposed construction and land use policies to prevent and mitigate the impact of landslide hazards. Questions in the Buildings Application that a constructor has to fill in for the approval of local government authorities is a classic example. "For a house in Colombo, you have to state the distance from the house to the sea level," an NBRO official explained. "The same question is asked for a house in Kandy or Nawalapitiya where it has no relevance or meaning! They should ask about the slope gradient of the land on which the house is being built and what kind of land cuts are being made. This could be related to future landslides." NBRO's Sri Lanka Urban Multi Hazard Disaster Mitigation Project attempts to provide a system of guidelines which national and municipal level officials in Ratnapura, Kandy and Nawalapitiya areas could adopt in disaster mitigation. "From last year, our funds have diminished from Rs. 22 M to 9M," R.M.S. Bandara says. "The Government can't provide all the funds we need for expanding disaster mitigation and development. We will appreciate more funds from any outside source!" Phenomena which could result in landslides 1. Excessive rainfall spread over a long period of time. 2. Sudden or progressively widening of cracks on slope surfaces or walls of buildings. 3. Sudden or progressive tilting of trees and towers on a slope. 4. Sudden oozing of water on a slope and continued water logging through poor slope drainage. 5. Subsides or heaves on a slope. 6. Spurts of rock falls on unstable upper slopes. 7. Subsiding roads and bulging roadside retaining walls. 8. Unusual behaviour of domestic animals and birds. Most hazardous landslide prone areas in Sri Lanka 1. Kegalle - Bulathkohupitiya, Aranayake 2. Badulla - whole district 3. Nuwara Eliya - whole district 4. Nawalapitiya - around the town BOX This year's Landslides (courtesy:NBRO) 1. April 23 - Demodara - near a stone quarry - 02 dead and 08 critically injured. 2. April 29 - Sarnia Estate - Badulla - 05 dead and 06 injured. 3. 08 May - Aranayake and Dehiowita - Pre-signs of landsliding observed in: Welimada and Drayton Estate housing scheme, Kotagala. BOX If landslides occur in your area or show signs of occurring, contact NBRO: Tel.01-588946, 501834, 503826. |
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| Editorial | Security Produced by Lake House |
It is a silent terror that stalks the hills and mountains, specially
when rains lash the heaving earth. In its grip, entire landscapes
disappear, carrying houses, trees, moving vehicles and lives with it,
before one is even conscious of it.
