Stop Press: Over 200 people buried in last night's landslide in Niteroi, Brazil?

AP is reporting that over 200 people have been buried in last night's landslide in Niteroi, Brazil:

"A top Rio de Janeiro state security official says at least 200 people have been buried in the latest landslide to hit the area. Civil Defense subsecretary Pedro Machado tells Globo television that the slide plowed into a slum in the city of Niteroi. Machado said Thursday that anyone there at the time was likely killed instantly."

O Globo's report also confirms that the landslide did occur on an old garbage dump, which was abandoned in 1986.

If over 50 houses were struck by this slide in the middle of the night a death toll of this order is certainly possible.

Another major landslide in the Rio de Janeiro area of Brazil

 O Globo in Brazil is reporting that another large landslide (in Portuguese "deslizamento de terra" for those looking the original website) struck the Niteroi area overnight, burying up to 50 houses, following the multiple slides yesterday.  The slide (shown below in an image from O Globo) occurred at Viçoso Jardim, in the Niteroi suburb of Cubango.  At least five people have been killed, with an unknown number of people missing.  The site is reportedly an old garbage dump that has subsequently been occupied by illegal dwellings.

Overall the toll from this multiple landslide disaster is very high.  To date the confirmed number of fatalities is 150, with 135 people injured and 40 or so still missing.  The Civil Defense agency is reporting 806 rainfall induced events, most of them landslides of various types. The reader-led O Globo map of the distribution of the events is a fantastic resource.  Hopefully it will be visible here:


Visualizar O mapa da devastação no Rio em um mapa maior


The landslides vary in size and nature considerably, but some are quite large, as this AP image shows:

Widespread landslides in Rio de Janeiro and Niteroi in Brazil

Over the last few days the city of Rio de Janeiro, and its twin city Niteroi just across the water, have been affected by extremely intense rainfall - a reported 288 mm in 24 hours.  The upshot has been a series of flash floods and landslides that have killed over 100 people so far.  More heavy rain is expected today.

O Globo has produced an interactive map of the Rio and Niteroi regions in which readers are invited to add information about their area.  This gives a first order estimate of the impacts of the rainfall:

Alagamento = flooding;
Lixo, lama e avores = garbage, mud and trees
Deslizamento = landslide
Postos de deocoes = Donation stations

It appears that many of the slides have affected the shanty towns constructed on the hillsides around the cities.  Over the next few days I will try to collate a list of the major fatality inducing landslides, but for now
O Globo has these two images of landslides that have affected residential areas:

Strangely, it is often a slightly abstract image that captures the horror of the event.  O Globo also has this exceptionally powerful photograph:

Finally, it is interesting to note that this rainfall event appears not to have been captured by the TRMM landslide warning system:

24 hours of rainfall (the yellow circles indicate those areas considered to be at risk of landslides):

72 hours of rainfall (the yellow circles indicate those areas considered to be at risk of landslides):

More later.

An update on the Italian landslide(s)

The large landslide in southern Italy that was graphically caught on camera (see the video in my earlier post) has generated a great deal of interest - indeed this site has had its busiest ever day. Details of the slide are still quite sketchy, but this is what we know so far:

First, the media are confusing two different slides in the same general area of Calabria - in fact there were about 100 altogether, but two are directly affecting towns. The one in the video occurred on the outskirts of Maierato, which is this town:

It appears that the slope had been moving for some days, and there are some indications that it was in distress well before this. The slide appears to have affected the area shown on this image, although I am waiting for clarification of this:

Interestingly, as Jonas van Rutte has pointed out to me, the roads near the headscarp appear to have been recently repaired, judging by the Google Street View images here. No-one was killed or injured in this landslide, although 2300 people have been evacuated from their homes.

The second slide occurred at San Fratello in Sicily, which is this town:

This slide appears to have damaged the centre of the town, leaving 1500 people homeless. The level of damage is high (image from Corriere della Sera):

Mudslides in Rio de Janeiro, Brazil

Various international news agencies are reporting that the year is ending with a number of fatal landslides in and around Rio de Janeiro in Brazil. For example, the BBC report says:

"Heavy rains have caused floods and landslides in Brazil, leaving at least 11 people dead. Officials said the worst incident had occurred in Jacarepagua, in the western part of Rio de Janeiro state, where a family of five died in a landslide. The state has been hit by 24 hours of downpours threatening new year celebrations on Copacabana Beach"

Whilst the report on AP says:
"Heavy rains in the Rio de Janeiro area have triggered mudslides that have killed at least 18 people. Rio de Janeiro state's Office of Civil Defence says that more deaths are likely as more rains are expected."

A quick look at the TRMM cumulative precipitation graphs for this area suggests that it has suffered from a prolonged period of heavy rainfall, mostly falling in heavy rainfall events:

Further rain is forecast for the next 24 hours.

Brazil landslides

Over the last month Brazil has suffered terribly from heavy rainfall that has induced extensive flooding and landslides. Over130 people have been killed to date.

This week, Minas Gerais state has been heavily affected. The Latin American Herald Tribune has today released this image of some of the damage. It shows how small, shallow soil slips are causing extensive damage to houses.

Retaining wall collapse, Uganda

On Tuesday morning a collapse occurred in a retaining wall being constructed for the foundations of a new tower block in the capital of Uganda, Kampala. Two images have been published online of the failure, which buried nine workers, killing eight of them:

Monitor online image of the Pensions Towers collapse site

New Vision image of the Pensions Towers collapse site

Collapses like this are now quite rare in more developed countries, though not unknown (see here, here and here for example). However, a properly designed retaining wall, based on good site investigation and laboratory data, and a properly executed design, should not collapse in this way. So it will be interesting to find out what has gone wrong in this case. There will be a formal investigation, so we will wait and see, but the pictures and reports do point to a couple of issues.

First, the pictures above show a very red soil. This is of course characteristic of deep weathering - the red is iron oxide. Deep, tropical residual soils like this are often problematic materials because they can be weak and also highly variable. Experienced engineers know to treat them with respect.

Second, the pictures show that the excavation is deep (one of the newspaper articles suggests it was 25 m high!). The wall was being supported, but it appears that this was with nothing more than "wood, iron bars and wire mesh" see here). The images suggest that the wall was just being faced, not supported properly. This is surprising. However, the reasons behind this are perhaps explained by this:

"At the heart of the queries will be NSSF’s decision to change building plans which KCC insists it had advised the developer against. In building Pension Towers, NSSF had initially planned an eight-storey tower consisting of two-basement parking levels. The Fund subsequently changed the plans for the complex, into a 26 storey complex and tripled its costs from Shs36b to Shs120b."

The suggestion being that as a result of the extra storeys on the tower the excavation was deepened from two to four storeys without taking into consideration the need to change the design of the wall. It has also turned out that:

"The developers of the Pension Towers, whose retaining wall collapsed on Tuesday killing eight people, had earlier ignored a warning from Kampala City Council advising against using unapproved building plans."

The state of play at the site might be indicated by this report into the aftermath of the collapse:

"When the New Vision visited the site around 11:00am, the horrified workers of [the] construction company were desperately trying to dig out their buried colleagues, using spades and hoes. Enraged onlookers demanded that the two bulldozers on the site be used to remove the soil. As fate would have it, the wheel chain of one of the bulldozers broke off as soon as the engine was started by a volunteer as its operator had vanished, while the second bulldozer developed a mechanical fault and caught fire. A third bulldozer had to be rushed in from another...construction site. "

Finally, the interplay between western and traditional views of disaster causation on sites like this is nicely captured here:

"Foreman Hajji Kigongo said the accident could have been prevented if they had sacrificed three bulls before construction began. He scolded this boss for failing to perform the ritual, a common practice in Buganda. Susan Kataike, the works ministry spokesperson, said prior to the works, they had tested the soil to establish if it could hold a building of that size."

Catastrophic rockfalls in the Middle East

The terrible landslide at El Doweiqa in the Manshiet Nasser slum in Cairo (see earlier posts here and here) continues to shock. The death toll has now reached 45 people, with many more still buried in the debris. News reports suggest that there is growing dissatisfaction with the response of the authorities in Egypt. To be fair, relatives in disasters such as this are often very frustrated at the speed of the response - for understandable reasons. Excavating blocks as large as this whilst keeping the rescuers safe is a terribly difficult task.

However, of interest is the similarities between this disaster and one that occurred in Yemen on 28th December 2005. This landslide occurred at the village of al-Dhafir, about 50 km from the capital Sanaa. As with Manshiet Nasser, the landslide occurred as a result of the collapse of massive bedrock blocks from an escarpment. Again, as in Cairo, houses were utterly flattened by the landslide. This disaster killed 65 people. The images below of the disaster are from AFP via the BBC. The similarities to the Cairo event are clear:


I have very rarely seen landslides like this from other parts of the world. What is unusual is the size of the blocks (huge) and the mechanism of failure (toppling). This combination is not seen very frequently. So why does the Middle East suffer this type of unusual failure?

I suspect that the answer lies in an unusual juxtaposition of geology and climate. The geology provides a strong rock with a simple joint set in which the spaces between the joints are large. This allows rare detachments of very large blocks. If the rock was weaker or more closely jointed then the blocks that fall off would be smaller - i.e. there would be more falls, each of a lower volume. The climate element comes from the aridity, which means that failure is not triggered by the pore pressure effects seen elsewhere. An additional factor is probably that the dry climate means that the rate of weathering is low. So a wetter climate would probably trigger more failures, each of a smaller volume.

The reports in Cairo suggest that the local people feel that water (or sewage) leaking into the rock has been a factor. This may be the case, although the mechanism of failure is not obvious. I would be interested to know if the slope has been quarried either officially or unofficially. For example, have pieces been hacked out to be used for building stone? Or have pieces been detached to create space for more buildings? This is so often the cause of rock slope collapses in inhabited areas.

Early reports of a rockslide disaster in Egypt

The newswires are providing early reports of a terrible rockslide at Deweka (also reported as Bekheit and Manshiyet Nasron) on the outskirts of Cairo in Egypt. The slide appears to be a rather strange failure of a rock slope, releasing huge boulders that have buried several (and possibly many) buildings.

This Al Jazeera post contains a very useful report and also has this image of the site:


They are reporting that "Officials said at least eight rocks, some measuring 30m high, had buried more than 50 homes in the poor district of Manshiyet Nasron on Saturday. At least 18 people have been declared dead and 35 injured. Some estimates put the number of buried at 500."

Early reports like this often over-estimate the losses in an event such as this, but if these boulders have hit residential buildings then the toll could be terrible. Al Jazeera also note that "In a survey carried out by UN Habitat, a human settlement programme, Manshiyet Nasron is described as "the largest squatter/informal area in Cairo. There are 350,000 persons living in this area on about 850 acres with a gross residential density more than 400 persons/acre".

"The area is suffering from poor living qualities, inadequate services, lack of infrastructure, and deteriorated environmental conditions. The site is characterised by sharp contour variations ranging between 56 and 200m," the survey said."

The final point to note is that Al Jazeera claim that "Manshiyet Nasron residents had informed the authorities a year ago that there was a split between the rocks, a potential danger to the homes below." This would make sense as the image above seems to show dry conditions and there are no reports of an earthquake. Thus, the landslide is most likely to have been caused either by progressive failure (i.e. a slow loss of strength through time) or slope cutting.

I will post again when I have more.

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.

UPDATE 3 (1st April 2008): Landslide in Alesund, Norway

Over the last thirty years or so there have been a series of nasty landslides under apartment blocks on the edge of cities. Examples that spring to mind include:

1972: Po Shan Road, Hong Kong - 67 fataltities
1993: Highland Towers, Kuala Lumpur, Malaysia: 48 fatalties
1997: Lincoln Mansions, Hsichih, Taiwan: 28 fataltites

On 26th March 2008 there was an interesting landslide in the picturesque town of Alesund in Norway, once again on a slope under an apartment block. The slide is well captured in this EPA image:

EPA Image of the landslide in Alesund, from the Monsters and Critics website

The impact on the apartment block is evidently devastating, as this image shows:

EPA Image of the aftermath of the landslide in Alesund, from the Monsters and Critics website

According to reports, the landslide has moved the building forward by about 6 metres, triggering collapse of the bottom two floors. About 20 people were in the building at the time, of which 15 escaped by five are believed to be buried in the rubble. Given the collapse of the lower floors and a propane tank fire, which was still burning 24 hours later, their chances of survival are negligible .

The timing of the landslide is interesting as there was no significant rain recorded. This is however the snow melt season, so perhaps the slide was triggered by this. The presence of that large hillock behind is slightly intriguing. I would be very interested to see what stabilisation measures were in place on the steep slope above the apartments. Unfortunately the Google Earth imagery is too low resolution to see.

This type of slide does illustrate the hazards of building on sloping ground on the edge of urban areas, something that humans are doing increasingly often. If catastrophic landslides like this can occur in a country with a high level of regulation and expertise, such as Norway, the hazards in less developed countries should be clear.

Update:
Aftenposten has an interesting article on, and a revealing of, the landslide here. This picture is this one:

Aftenposten image of the aftermath of the landslide in Alesund, taken from the air

The image shows that the slope was indeed very steep and that the building has indeed been pushed forward. The article indicates that a row is breaking out over who is to blame:

"Speculation over the cause of the landslide continued to rage. One geologist said he'd warned that the hill behind the building, completed just four years ago, could give way. Others, however, said it had been secured and the building's developer and contractor claimed all regulations and re-enforcement measures had been followed. City officials had issued building permits after approving plans submitted."

I would suggest that there is a clear need for a genuinely independent investigation of this event, with an emphasis being placed not on blame but on learning the lessons in order to prevent future accidents like this.

Update 2: 28th March
Aftenposten has a second article about this slide here. A few issues emerge:
1. The land owners upslope from the landslide are now understandably concerned for their safety
2. Apparently "Parts of [the hillside] had been blasted away six years ago to make room for the building at Fjelltunvegen 31, and questions are being raised over whether that weakened the ground and contributed to the landslide." I am not sure that the blasting would have weakened the ground, but it was certainly have been over-steepened.
3. "The blasting experts, developers and builders of the complex all have been quick to contend that they followed all rules and regulations for such projects, which are common in Norway. They also point out that they had reinforced the hillside behind Fjelltunvegen 31 with as many as 123 bolts." So it appears that rockbolts had been used to stabilise the slope. Given the size of the failure, I wonder how long they were? There is certainly no evidence of pulled out rock bolts on the photo, which suggests that they didn't reach the surface that failed. The first picture above shows that sliding has occurred on a remarkably planar surface - this is surely a pre-existing discontinuity?

Update 3: 1st April 2008
Aftenposten has now published another image of this landslide:

Aftenposten image of the aftermath of the landslide in Alesund showing the material and the block

This picture is very helpful as it shows that:

1. The landslide has occurred in bedrock;
2. The failure has occurred on a pre-existing joint that is inclined towards the building;
3. The joint surface appears to have either weathered material or gouge on it. The strength of this is certainly much less than that of the intact rock mass;
4. The lateral boundary of the slide is another joint;
   
5. There is little evidence of the rock bolts on the joint surface