George Town: another serious landslide in Penang

Heavy rainfall in George Town, Penang overnight has triggered another significant landslide in Malaysia.  This new landslide, which fortunately did not kill anyone, occurred close to the Tanjung Bungah landslide last month.  Once again the slide has occurred at a site under construction.  The New Straits Times has an article about the landslide that includes this image:-

New Straits Times image of the landslide at George Town in Penang, Malaysia yesterday. Image by RAMDZAN MASIAM.

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The houses upslope from the failure are newly constructed and are reportedly empty at the moment. This image, also from the New Straits Times, shows the damage to them and to the road:-

Damage to the road and houses caused by the landslide in George Town, Penang. Image via the New Straits Times / RAMDZAN MASIAM.

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This is clearly a rotational failure in an engineered slope with a retaining structure.  I suspect that the landslide involves fill behind the retaining wall, presumably emplaced to create the bench for the houses and road.  It seems to me that the slide surface may well extend beneath the footing of the retaining wall – it can be seen to toe out in the disturbed vegetation downslope from the wall in the first image.  It would be interesting to know how deep the foundation of the wall extends.

Rotational failure below the footing of a retaining structure is a well-known hazard, and the design of the wall should consider this problem, and ensure that it does not materialise.  In a structure so new it is possible that this is an error in the design and/or construction of the retaining wall and associated works.  A proper investigation is needed to decide.

Penang has now suffered two major construction-related landslides in less than a month.  This must be a real source of concern.