Saturday 26 May 2012

Landslides at Doorstep

In Sri Lanka, landslides are at our doorstep

Act fast!!

Chandima Gomes

News reports on mild earth tremors recorded in several parts of the country during the last few days joggled some chilling memories in my mind.

In January 2008, I went right up to the Indian boarder from Pakistan side. I was on a research mission to Azad Jammu Kashmr to investigate landslide effects due to 2005 earthquake. A rare chance that a non-Pakistani would ever get.

Encircled by Jhelum  and Neelum rivers, Muzaffarabad, the scenic capital city of AJK was still weeping, three years after the disaster. The above picture shows the Valley of Death where over 12,000 people are still buried at few meter depth. It is a feeling that I can never put into words..thinking of the 3 busy villages with ever smiling Pakistan villagers, which now have turned into a ghostly layer of rubble and rock. 

The small townships have more cemeteries than post offices, schools or hospitals. Many surviving built up areas were on loosely bound sedimentary soil layers that may give up at any time. Several fault-lines were running right across the city centers. It was like living with a death warrant in one hand.

Back in Sri Lanka, for the following two years where ever I visit, for whatever purpose, I kept my eyes opened for the following signs that are forerunners for an inevitable landslide, sooner or latter. 

  • Springs, seeps or highly moist soil in areas that have not typically been wet before
  • New cracks or unusual bulges in the ground, street pavements or sidewalks.
  • Soil moving away from foundations.
  • Ancillary structures such as decks and patios tilting and/or moving relative to the main house.
  • Tilting or cracking of concrete floors and foundations.
  • Broken water lines and other underground utilities.
  • Leaning telephone poles, trees, retaining walls or fences.
  •  Offset fence lines.
  • Sunken or down-dropped road beds.
  • Rapid increase in creek water levels, possibly accompanied by increased turbidity (soil content).
  • Sudden decrease in creek water levels though rain is still falling or just recently stopped.
  • Sticking doors and windows, and visible open spaces indicating jambs and frames out of plumb.
  • A faint rumbling sound that increases in volume is noticeable as the landslide nears.
  • Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.

While making eye observations and other visual inspections, I also talked to people in the localities and checked whether they have noticed above symptoms elsewhere in the area.

Shockingly, I have found that there are number of areas in Sri Lanka which have severe threats of encountering mass scale landslides in the near future. District-wise Ratnapura, Kegalle, Kandy, Nuwaraeliya, Badulla, Matale and some parts of Matara, Galle, Monaragala and at a lesser extent Colombo and Gampaha districts are facing landslide threats.

There are several locations of the upcountry railway line where the chance of sudden earth slip/sink is highly probable. Such event in the presence of a train may be a major disaster. Similarly there are various, parts of several main highways and byroads which may encounter debris fall at any time.  

Many of my interviewees mentioned that they observe increasingly worsening landslide symptoms since year 2005, which is coinciding with 2004 December tsunami

Those who have basic knowledge on concepts of geology may understand that even mild earth tremors may rapidly accelerate the triggering of landmasses which are loosely hanging over the slopes. Thus, with torrential rains predicted for the next few weeks, chances of having mass scale landslides are very high. 

For the benefit of the public, places vulnerable to undergo landsliding are listed below

  • On existing old landslides
  • On or at the base of slopes
  • In or at the base of minor drainage hollows.
  • At the base or top of an old fill slope.
  • At the base or top of a steep cut slope.
  • Developed hillsides where leach field septic systems are used

In Malaysia, for an example, a large number of research projects are carried out to stabilize land masses which are prone to slide. Most of these research started as calamities at catastrophic level took place in 90s. Following the outcomes of these projects legislations are formulated on regular basis for proper land usage and building construction.  

In Sri Lanka, the studies of landslides are mandated to National Building Research Organization (NBRO). I think it is the high time for them to go beyond zonal-mapping (landslide site identification) and issuing warning to the public for evacuation. 

Let the university academics be motivated to start research on landslides which is a dire need of the hour in the country

No comments:

Post a Comment