Landslides do not kill, unsafe slopes do

by Donovan Mujah

During my postgraduate studies in one of the top engineering universities in Japan in 2011, my Japanese professor raised this question – “Natural disasters such as landslides, tsunamis and earthquakes are beyond our control. As engineers, we work towards minimising their impact on society. But how do we define engineers? Are they defined by the number of high impact journals they publish or by their contributions towards the betterment of society?”

Every year, thousands of people in developing countries are killed, injured or left homeless due to landslides. The potential for disasters increases as rapid urban development takes place. More and more houses are built on steep, unstable slopes using poor quality materials and guided by unsafe building practices.

The tragic landslide in 2007 at Kampung Baru Cina, Kapit, Sarawak which resulted in two villagers being buried alive and nine wooden houses destroyed, and the one that befell the Hidayah Madrasah Al-Taqwa orphanage in FELCRA Semungkis, Hulu Langat, Selangor in 2011 in which 16 people were killed, are grave reminders of how vulnerable communities are to disaster.

Landslides occur when the stability of the slope changes. The changes in stability can be caused by a number of factors in which a disaster can be influenced by one factor or a combination of various factors. The natural causes of landslides include:

  • Groundwater (pore water) pressure acting to destabilise the slope.
  • Loss or absence of vertical vegetative structure, soil nutrients and soil structure (for example, after a wildfire where it can last up to 3 to 4 days).
  • Erosion of the toe of a slope by rivers or ocean waves.
  • Earthquakes adding loads to barely stable slope.
  • Volcanic eruptions.

Landslides are also prone to be aggravated by human activities such as:

  • Deforestation, cultivation and construction which destabilise already fragile slopes.
  • Vibrations from machinery or traffic.
  • Blasting.
  • Earthwork which alters the shape of a slope or which imposes new loads on an existing slope.
  • Removal of deep-rooted vegetation that binds colluviums to bedrock.
  • Construction, agricultural or forestry activities (logging) which change the amount of water that infiltrates the soil.

Landslides are a man-made problem caused by poverty, lack of building standards and enforcement, and lack of access to affordable materials, skills and tools to build safe infrastructures. In the case of Malaysia, there is also a lack of more focused research in landslide prevention.

The massive loss of life is absolutely preventable. It just takes the right training, approaches, incentives and small changes in construction practices to save lives.

There is a sustainable solution to this man-made problemIn 2010, I went to Gansu, China on a Chinese Government Scholarship (Great Wall Programme) fellowship to study and assist with post-disaster reconstruction efforts after a devastating landslide that killed more than 1,500 people. Through my observations, I learned these important lessons:

  • Housing construction is part of development. Like any other development challenges, it comes down to technology, money and people.
  • Landslide-resistant construction in developing countries will become common only if the right technology is locally available, widely known and culturally accepted.
  • The cost of the technology must be competitive with existing but not necessarily safe building methods.

After putting this theory of change to the test in India and China, I have observed that homeowner-driven, post-disaster housing reconstruction not only builds local capacity, creates jobs, stimulates the local economy and builds resiliency, but also creates an ecosystem in which disaster-resistant construction becomes the norm.

In fact, this approach is gaining popularity around the world. In India and China, it is the preferred method. It is also the preferred method in Bangladesh after the hard lessons learned from the Chittagong landslide which claimed more than 127 lives. In Haiti, large aid agencies have switched from more costly, donor-driven approaches for post-disaster housing reconstruction to less costly and more environmentally friendly homeowner-driven approaches, with a lower cost per impact and long-term, sustainable outcomes.

Landslides do not have to be disastrous. Communities can build resiliency and reduce risks. According to the United Nations Development Program (UNDP), for every dollar spent on disaster preparedness, 7 dollars is saved in disaster response. The return on investment is exceptional, not to mention the thousands of lives saved.

The same sustainable, homeowner-driven approach to housing reconstruction after landslides can be applied in a pre-disaster setting to reduce the risk for disaster. The same principles apply – determine no or low-cost improvements to construction methods, build local capacity, and work with governments to develop and enforce simpler yet safe building codes and involve the homeowner.

A key step in a pre-disaster setting process is facilitating access to capital that is contingent upon meeting minimum standards for construction quality. By working with financial institutions to bundle house financing with technical assistance, homeowners who may not normally qualify for home loans can make life-saving improvements to their houses before a landslide happens.

At Curtin Sarawak, I am currently leading research into minimising the impact of landslides by installing multiple rows of small diameter steel piles (SDSP) into the potential slope slip surface. The use of SDSP to reinforce slopes, however, is not new as it has been widely utilised in countries like the United States, Japan and Germany.

Some time ago, the technique was introduced in Malaysia to cope with landslides that were occurring more frequently. Though we are still at the preliminary study stage, analysing the effects of installing SDSP to slopes and focusing on the failure mechanisms of such a technique to soil movement in numerical simulation, future research will be directed towards looking at these effects on a full scale model in the field.

So far, the results of our study have shown good correlation with other conventional techniques in slope reinforcement. This set of data justifies the use of SDSP as a plausible slope reinforcement method in Malaysia.

It is hoped that this research will create a better understanding of the causes and effects of landslides and help minimise their impact on our communities. Most importantly, this research can teach our communities one simple truth – that landslides do not kill people, unsafe slopes do.

Donovan Mujah is an associate lecturer in civil engineering in Curtin Sarawak’s School of Engineering and Science. He is a graduate member of the Institution of Engineers Malaysia, Miri Branch and also a graduate engineer registered with the Board of Engineers Malaysia. Donovan can be contacted at +60 85 443939 ext. 3956 or by e-mail to dmujah@curtin.edu.my.

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