Garbage dump landslides

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.

Deaths and research in landslides

Now that the Tangjiashan crisis is over, it is clearly time to move on to other things. I will post
a retrospective on that event when the dust has settled. For now I think we should allow the Chinese to bask in the success of their achievement.

To change the topic, I thought it would be interesting to post an analysis that I did a couple of years ago. The analysis was simple but quite fun - I looked at the landslide fatality database for 2003 and 2004 by calculating the proportion of fatalities by large geographical area. I then looked at the field areas of the research presented in the Springer journal Landslides and in papers presented at a selection of international landslide conferences, and worked out the proportions as per the fatalities.

Now ideally there should be some relationship between the locations of landslide deaths and the locations of landslide research, one would hope. Care is needed as:
1. One year of landslide data might not be representative; and
2. The sample of the areas of research might not be representative.

However, the plot does show how far we are from an equitable situation:


In my simplistic world I would hope that most areas plot close to the central line on the graph. In most cases this is clearly not so. The regions with really serious landslide problems in this period - Central America, SE. Asia and S. Asia has a tiny proportion of the research. Regions that dominated the research into landslides - North America and Europe - had very few landslide fatalities. Only East Asia looks to be in the right place amongst those regions with large numbers of both research projects and fatalities.

Two things emerge:
1. Care is needed because in 2004 landslides in Haiti caused huge problems, which mean that for this period Central America dominates the statistics. If we were to take the period 2002-2006 East and South Asia would dominate the fatality count.
2. Only E. Asia appears to have the balance right between research and fatalities. This reflects the large landslide programmes in China, Japan, Hong Kong and Taiwan.

Of course the picture might look different if this were to be examined through the lens of economic losses rather than fatalities, but not I suspect if we were to normalise by GDP or per capita income. All of which serves to highlight the fact that the landslide research community should shift its focus if it really wants to make a difference by saving lives.

I will try to do a better analysis of the full dataset over the summer, but thought it would be interesting to share this initial analysis.