The 2009 fatal landslide map and statistics

This post presents the data from the Durham University Fatal Landslide database for 2009. First, this is the map of fatal landslides. Each red dot represents a single landslide recorded on the database. Click on the map for a better view in a new window:


The map shows the usual distribution. Note the high incidence of landslides in SW India, the Philippines and in java in Indonesia. The high occurrence of landslides along the southern margin of the Himalayan mountain chain is also clear, but is less continuous than usual. This reflects the 2009 monsoon rainfall pattern, which was substantially below average, especially in the northwest of India, as the map below (for India only), from Monsoon Online, shows. The map indicates the departure from the mean annual monsoon rainfall:

In terms of statistics, the key data are:

• Number of recorded fatal landslides: 493 (this is substantially above the long term average).
• Number of recorded fatalities: 3611 (this is substantially below the long term average, primarily because there were no large earthquakes in populated mountainous areas).

Fatal landslides in July 2009 - map and report

Below is the fatal landslide map for July 2009. Each yellow dot represents a single landslide that killed a person. The background is the etopo1 DEM, with the darker colours representing higher terrain. As usual clicking on the image should provide a high resolution view. The image is a GIF so you should be able to download it, but please acknowledge the source.

You will see that in July the focus has very much switched to Asia, with the effect of the (weak) monsoon along the length of the Himalayas being fairly clear. Note also the clear evidence of fatal landslides in Central China, reflecting the heavy rainfall there, and in Japan. There is very little going on in the Caribbean and in SE Asia at the moment - this is not unexpected for the time of year.

The statistics are as follows:
Number of fatal landslides: 65
Number of fatalities: 366

The average for July for 2003-2008 was 468 fatalities, meaning that 2009 was substantially below average. The cumulative number of fatalities for 2009 is 1328 to the end of July, substantially lower than the long term average cumulative total of 1574 (excluding earthquakes of course). Indeed, only one year (2008) has had a lower cumulative total at this point.

Comments and corrections are welcomed. Thanks to all who have helped to put this together.

June 2009 fatal landslide map

A little late, but here is the map of fatal landslides for June 2009. Regular readers will note a change in the quality of the map (for the better I hope). My achievement of the week is to teach myself GIS from scratch, so that now I can plot the data on decent quality maps. So here it is, plotted on the SRTM digital terrain model (Click on the map for a better view in a new window):
In total I recorded 22 landslides killing 155 people worldwide. Each dot above represents a single landslide. Sharp eyed readers will note that there is one missing from the above - there is a landslide in China that I have not yet located. The number killed is well below average (255 fatalities) for June, primarily because there are far fewer landslides in S. Asia than is normal for this time of year.

Guatemala landslide - new satellite image

The Advanced Land Imager instrument of the NASA Earth Observation satellite EO-1 has recently collected an image of the Guatemalan landslide, which they have made available online. The image is here. I have cropped it to show just the slide - it is quite useful:

Costa Rica Earthquake - the aftermath

I thought a brief follow up email to my previous posts about the Costa Rica earthquake would be useful now that we are five days post the event. So what do we now know?

Well, first the final death toll is likely to be about 40, most of whom were killed by landslides. Officially, as of today, 19 bodies have been recovered and 21 more are buried under landslide debris. It is possible that there is a small number of addition casualties under collapsed slopes. Landslides continue to occur during aftershocks and there is growing concern about the potential for future slides (see image below). Initial estimates of the damage are $100 million. In a country with a GDP of $26 billion, this is a huge amount (in comparison, the GDP of the UK is $2.13 trillion, meaning that the equivalent loss in terms of GDP would be $8.2 billion). Estimates are that the earthquake destroyed 518 houses, triggered the loss of 16 miles of road and collapsed eight bridges. Of course there will also be a substantial hit to tourism, which is vital in this area.


In terms of landslides, the emergency management office has indicated that the earthquake triggered more than 246 landslides. Repair of roads damaged by the landslides is expected to cost $15 million (see image below).

Landslide hazard and the Guatemala rockslide

As commenters on my earlier threads have pointed out (thanks to them), the location of the landslide in Guatemala can now be pinpointed using a map produced by CONRED. This map comes from a very useful report, with some good images of the rescue and recovery operation, available here. I have reproduced the map below (click on the map for a better view):

Helpfully, this allows the location to be pinpointed on Google Earth (unfortunately the high resolution imagery starts just east of the landslide location - click on the image for a decent view):


Satellite imagery can be difficult to interpret until a 3D perspective is available. This is one of the key strengths of Google Earth. The situation becomes so much clearer when a perspective view is taken:

A magnified and annotated image below shows that the landslide occurred in a very clear bowl shaped feature that would cause any good geomorphologist to be very nervous in terms of slope stability. I have highlighted the boundary of the bowl and the location of the landslide:


Note that there are a number of other locations that look vulnerable to slope instability as well, such as the bowl to the east of the area that failed. Reports suggest that the authorities are being cautious and have arranged evacuations. This is probably prudent, but it is important that a proper hazard assessment is undertaken, and that the risks associated with landslides are then balanced against the (social) risks to the people associated with moving them from their homes and their land.

The Guatemala landslide - video of the failure in December

The Guatemalan landslide becomes more interesting by the day. It is now apparent that the first failure, which occurred on 14th December and killed five people (the remains of three of whom were not recovered) was also caught on video. This is available on Youtube. I have embedded it below, so should work:


If not, then it can be viewed here.

Guatemala landslide

As the Guatemala landslide now fades from media prominence, Reuters have released probably the best image to date of the landslide site:

It is now clear that this was a a large rockslide (not a mudslide as reported elsewhere).

AP have released a good image of the site:


Whilst this Reuters image shows the runout of the landslide quite well:



Finally, CONRED released this image of the site to show the ongoing rockfall activity that caused suspension of rescue operations:

Meanwhile the number of recovered victims has now reached 37. About 50 victims remain buried in the debris.

Finally, there are various reports that an evaluation of the site has determined that the area around the landslide is too dangerous for habitation. My suspcicion is that this is right - the landslide appears to me to have occurred in a much larger landslide scar. I will post again on this soon.

Another video of the Guatemala landslide

It now appears that there are two videos of the Guatemala landslide. The second one, which is not as clear as the original, has appeared on the Telediaro 3 web site. It can be viewed here:

http://www.telediario.com.gt/index.php?id=15366&tim=#

Meanwhile, there remains considerable uncertainty as to the number of victims (we may never know for certain I suspect), whilst speculation is intensifying regarding the cause. Given the clear size of the landslide (see the video plus the image below from Prensa Libre), comments elsewhere that road widening was the primary trigger look to be wide of the improbable. Clearly there is no record of seismicity or of intense rainfall (everything looks dry in the video). The most likely trigger is therefore progressive failure, which is consistent with reports of increased activity in the fortnight before the failure, reports of the slope emitting noises and the fact that the road had been closed prior to collapse.


Finally, there is continued concerns that a second major failure might occur given the oversteepened nature of the upper part of the slope.