22 June 2008

Garbage dump landslides

Posted by Dave Petley

News today of a garbage dump landslide in Guatemala City on Friday that is believed to have killed at least 50 people (Fig. 1) has set me thinking of the hazards of these types of mass movements . The slide in Guatemala appears to be fairly typical of these events – a large number of very poor people who were scavenging for recoverable items in a dump that was known to be dangerous were buried by a sudden slide.

Fig. 1: Rescuers recovering the body of a victim of the 20th June 2008 garbage dump landslide in Guatemala City. Image from AP.

A quick scan of the fatal landslide database for large (>10 deaths) events of this type showed that I have recorded at least seven large-scale garbage landslides since 2000 (Table 1), responsible for a recorded 571 deaths. Of course this is probably very much the tip of the iceberg as:
1. I have only looked at the large events; and
2. It is very likely that most garbage landslide events go unreported, given the locations and the people involved.

Table 1: Large-scale (>10 fatalities) garbage landslides recorded in the fatal landslide database. This is undoubtedly just the tip of the iceberg. Note the death toll for Guatemala City is provisional at this stage.

Garbage landslides are particularly horrible events. For most people being buried alive raises an inbuilt fear, but the thought of being buried by garbage is particularly unpleasant. In addition, garbage often releases toxic gas, which means that victims may die from poisoning whilst awaiting rescue. Garbage also generates heat, which means that the victims may be die from hyperthermia. In extreme cases the garbage may ignite.

So why do garbage landslides occur so frequently? Sadly, a substantial number of people in less developed countries make their living from garbage scavenging. Many of these people live amongst the rubbish as well. The numbers are staggering – for example, the Stung Meanchey municipal rubbish dump on the outskirts of Phnom Penh has 3,000 scavengers, 1,000 of whom are believed to be children. Life in such an environment is hard – garbage dumps are by definition unhealthy places that are also physically dangerous. Ironically of course these people are performing a valuable public service by recycling metals, plastics, etc, from which the rest of us benefit. The garbage is typically dumped by truck with little thought for the safety of the scavengers to form steep slopes (sometimes up to 70 degrees). Garbage sites are often on slopes anyway as they occupy land that is not ueful for development (Fig. 2).

Fig. 2: BBC News image of the Payatas garbage dump in the Philippines, illustrating the steep slopes often associated with these locations. Note the houses at the bottom of the slope – it is unsurprising that fatalities are frequent in such locations. It was in this dump that nearly 300 people were killed by a garbage slide in 2000.

The garbage pickers themselves then unknowingly destabilise the piles by removing material from the base, whilst heavy rain often triggers landslides as well, as happened in most of the cases above. Most of the slides are small, often killing just a few people. It is likely that such slides are very common, but the majority undoubtedly go unreported.

A quick search of Web of Knowledge showed not a single paper on garbage landslides. I guess this type of research is not very attractive, but if ever there was a landslide issue that needs attention then this is it! A study to try to determine the actual human cost of garbage slides would be a good first step, backed up by an analytical study of the mechanisms of garbage slides so that the people can be better protected. I am sure that the losses associated with garbage slides could be reduced without taking away these people’s livelihoods.