New images of the level of destruction in the Cusco area of Peru

The Spanish language blog El Caminerito has been covering the magnitude of the rainfall, flood and landslide disaster in Cusco, Peru. They have put together a very helpful map showing the locations of serious damage:


Ver Cusco en Emergencia en un mapa más grande

The scale of the disaster, which is still being ignored by the western media in favour of coverage of the tourists at Machu Picchu, is well-illustrated by these images of the Huacarpay region:


Meanwhile, via the Typeboard site, the Spanish language site Peru.com reports that the village of Zurite was severely damaged by a landslide, which sounds to be a debris flow (Google translation):

" the landslide of mud and stones covered the Plaza de Armas, the town’s Church, the main streets of the city and damaged 500 houses. The incident occurred about 3 pm on Thursday after they noticed a crack on a hill and began to take appropriate action, emergency services were able to evacuate the entire population."

This is the Google Earth imagery of Zurite:


There is no shortage of landslide scars on the hillside above the town, plus the quarries, one of which appears to have excavated out the toe of one of the scars.

Here is an image of the central square via the Panoramio site:

Landslides from the Haiti earthquake - not many!

NASA has today released an image, partly obscured by cloud, of the upland area to the south of Port-au-Prince. This is the area that received the highest levels of shaking and, given the terrain, was most likely to have suffered slides. The image is available here:

http://photojournal.jpl.nasa.gov/catalog/PIA12495

and a comparison with an image taken in 2008 is here:

http://earthobservatory.nasa.gov/IOTD/view.php?id=42333

Note that this area suffered heavy rainfall in the 2008 hurricane season.

This is a close-up of a part of the area, close to, and just to the south of, the fault:

Clearly there are landslides visible, but the number is comparatively low and for the most part the slides are small. Note that NASA has, understandably, marked them as being "potential landslides". The terminology used here might be interpreted as indicating the possible existance of a landslide, rather than an area in which a future landslide may occur. The big unknown is whether there is a higher likelihood of sliding in the next heavy rainfall event. This can only be addressed with fieldwork, but I am not sure who will do this (maybe the USGS?). It is also essential that refugee camps are located away from potential mudflow and debris flow tracks (the worse structure to be in during a debris flow is a tent - they offer no protection, but the ropes and pegs make rapid escape difficult). I hope that this will be taken into account as the situation stabilises.

Finally, servir.net has produced an erosion potential map for the earthquake-affected area, which is available here:

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).

New atlas of natural disaster threats in the Andes

On Friday the Andean Community of Nations (CAN) (Bolivia, Colombia, Ecuador and Peru) released an atlas of potential natural disasters affecting the countries of that region, which has come out of the PREDECAN project. It presents maps of the distributions of earthquakes, volcanic eruptions, landslides, flooding, frost and drought, with a special emphasis on El Nino / La Nina.

As far as I can tell this atlas is available only in Spanish (not unreasonably of course), but it is available online in its entirety, which is certainly one better than the World Bank hotspots project. Of course I am most interested in the landslides section - and this deserves more than a single post - but for now let me just give an overview of the landslides chapter.

The headline figures in the analysis are that between 1970 and 2007 about 11,000 people were killed and 38,000 homes were destroyed by landslides. About 260 landslides killed more than 20 people and/or destroyed more than 50 houses. El Nino is a key control on the occurrence of slides. The following map presents the distribution of fatal landslides, with the size of the spot representing the number of fatalities in each case. The darker grey area is the zone covered by this study:

The study also presents the results of an analysis of trends of occurrence of larger (20+deaths and/or 50+ homes destroyed) landslide accidents:

Clearly the data suggest that more landslides have occurred since the mid 1980's than before, but this may well be an artifact of the data. Note that since the mid 1990's there is no clear overall trend, although the period in the late 1990s characterised by the large El Nino event is clearly evident in the data. A moderate El Nino event is thought to be developing at present.

Typhoon Parma - rainfall and landslide maps

NASA have recently produced a map of the distribution of rainfall from Typhoon Parma (Pepeng) in the Philippines:

The map has been produced from "the Multisatellite Precipitation Analysis, which includes rainfall observations from many satellites that are calibrated to match more detailed rainfall observations from the Tropical Rainfall Measuring Mission". I am not sure how reliable this is, but it is certainly a useful first estimate.

I thought it would be interesting to compare the distribution of fatal landslides with this map. I have used the amazing NDCC daily reports to compile a map of the landslides that killed people. I can only locate the slides to within a couple of kilometres, but for this exercise that is good enough. So here is a Google Earth map of the fatal landslides:

Each dot is a single fatal landslide - click on the image for a better view in a new window. Note the cluster in the centre of the image - this is Baguio City where there were many slides.


Not a bad relationship actually, but far from simple - but then fatal landslides are certainly not simple things.

Comments welcome.

August 2009 fatal landslide map

Here is the fatal landslide map for August 2009. As usual each yellow dot represents a single landslide that killed one or more people:

Click on the map for a better (downloadable) view in a new window.

The statistics are as follows:
Number of recorded fatal landslides: 53
Number of fatalities: 782

In terms of fatalities this places August well above the 2002-2008 average (347 fatalities). Of course this is dominated by Typhoon Morakot in Taiwan, and in particular the landslide at Hsiaolin. However, the map shows clearly the impact of the SW monsoon along the southern edge of the Himalayas and also the impact of typhoons in E. Asia. Elsewhere there is the normal smattering of landslides here and there. The lack of slides in S. America is perhaps surprising. The paucity of hurricanes in the Caribbean means that this area is not figuring at the moment. I wonder if we will see a large, late season event.

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.

Fatal landslide map for 2009 to date

I have been a little remiss in posting these maps of late due to other pressures. Below is the distribution of fatal landslides that I have recorded in 2009 to date. Each red dot represents a single landslide that killed at least one person. All types of landslide (including debris flows and rockfalls) are included:


You can click on the map for a better version in a new window. One thing to note is that I have not heard of any fatal landslides from the L'Aquilla earthquake in Italy - but I would be surprised if there were none in reality.

Below I have plotted the same data, but colour coded the dots. In this case, the coding goes dark blue for January moving to lighter blue for February, blue-green for March, and light green for April and dark green for May:

It is reasonably clear that for Asia the blue colours cluster in the Philippines and Indonesia, whilst the greens are in South Asia. This is of course explained by the seasonality of rainfall.

For info, in 2009 to date I have recorded fatal landslides, killing 715 people. This is about par for this time of year, with the main landslide season about to begin.

Landslides and the UN's Global Assessment Report on Disaster Risk Reduction

The UN ISDR is today launching with a great fanfare the first Global Assessment Report on Disaster Risk Reduction. This report "provides hard-hitting evidence to demonstrate how, where and why disaster risk is increasing globally and presents key findings from a global analysis of disaster risk patterns and trends, including where high mortality and economic loss is concentrated. ." The report is online now and can be downloaded here.

I haven't yet had time to read the whole of the 200 page document - I will do so in due course - but have taken some time this morning to look at the landslide hazard / risk section in Chapter 2n. This was generated by the Norwegian Geotechnical Institute and has been peer reviewed by some eminent people. So how does it look?

I think a good starting point is to say that it has to be recognised that this is a very difficult thing to do. There are all sorts of problems in the collation and analysis of this type of data. However, I also have to say that I have some reservations about the outcomes, which don't to me seem to correspond to what we actually observe.

The landslides section starts with a premise that I find bizarre. The opening sentence is as follows: "Observed mortality in landslides triggered by high precipitation is approximately six times higher than in landslides triggered by earthquakes." Huh? No source or justification is provided for this statement. I just cannot see how it can be justified. In recent years we have large numbers of fatalities from landslides in the Kashmir earthquake and the Wenchuan earthquake, bit of which swamp the fatality signal from rainfall events. Perhaps this study was done before the impact of these events could be included, but there is plenty of documentation of mass fatalities from earthquake-induced landslides even before this event. Perhaps the problem here is that earthquake-induced landslides are included in the earthquake hazard section, but we should be under no illusions that the impact of this is ponce again to greatly under-estimate the risk associated with landslides. This is very frustrating!

The upshot is that the risk model considers only precipitation-induced landslides. We need to keep this is mind when evaluating the study. The headline result of the analysis seems to be (this is a direct quote) "The predicted mortality risk, even in very large countries such as India or China, is less than 100 deaths per year". Being blunt, if this is the mortality risk analysis then the model is frankly wrong as the measured losses are much higher than this. Taking 2008 as an example, a year in which precipitation-induced landslide occurrence was not exceptional, I recorded 778 rainfall-induced landslide fatalities in China, 700 in Haiti and 252 in India. This is typical and is supported by official figures. Of course, every few years these countries suffer a very large landslide disaster (e.g. the Leyte landslide in the Philippines), which increases the average annual numbers. Therefore, the study has fundamentally under-estimated the risks of rainfall-induced landslide mortality still further.

So let's take a look at the maps. They have produced landslide risk maps on a 10 x 10 km grid. Three maps have been generated, which I reproduce below. The maps are for Asia, Central America (plus the NW of S. America) and Central Africa, presumably because these are the three areas with the highest level of landslide risk. Click on the maps for a better view in a new window. Note that the label on the legend of "tropical cyclone risk" is presumably just an error, albeit a rather serious one.

This is my map of fatal landslides for 2006, 7 and 8. Each black dot represents a single fatal landslide:

This map is close to being a direct realisation of the mortality risk analysis, although care must be taken given the short time period that my map covers and to remember that population density may be an important factor. The first thing to note is that the C. American and Asian areas are well-chosen given the high incidence of fatal landslides that I record. I am far less sure of the African area - I really don't record much for that part of the world, although I recognise that this might be because I just don't capture events in this part of the world, perhaps. In Asia the distribution seems to be vaguely right in that it picks up the swathe of events through the Himalayan arc and the high risk in Java, etc. However, it does appear to fail to pick up the landslide risk associated with Central China at all well. This may reflect the high population density here (i.e. although there are lots of fatal landslides, the risk to individuals is low), but I doubt that this is the whole story. My feeling is that the analysis is failing to represent landslides in this area well. A similar problem occurs in SW India, which is a notable hotspot. In Central / S. America the analysis seems to do rather better.

Overall I am left feeling that the representation of landslide risk is really unsatisfactory. It must be possible to do this better. I hope that the analysis of the other hazards is rather better - I am sure that it must be.

Comments welcome.

December 2008 landslide map

I am just in the process of putting together my annual collation of fatal landslide statistics for 2008, together with the map of all the landslides, but in the meantime here are the statistics and map for December.

So first the data. I recorded a total of 16 fatal landslides in December, causing 46 fatalities. This is well below the long term average, which 149.8 fatalities. The largest event was the Kainantu Mine landslide in Papua New Guinea on 4th December, which killed 10 people. I guess the highest profile event was the Bukit Antarabangsa landslide near to Kuala Lumpur, which killed five people on 6th December. This has really dominated the news in Malaysia since.

Here is the map. You will see that I have taken the "copyright" statement off to make it more usable. Please do acknowledge this blog if you use it in presentations etc, and please don't publish it without my permission. Click on the map for a better view:


As mentioned above I will provide a proper commentary for the 2008 dataset in due course (might take a week or two), but in the meantime here is the provisional final map for 2008. As before, click on the map for a better view:

Comments and/or corrections welcome. One of my tasks for this year is to get a better mapping program than Versamap (suggestions welcome)...

Spatial patterns of deaths from natural hazards in the US

There is a very interesting paper in press in the International Journal of Health Geographics on the spatial patterns of mortality (deaths) from Natural Hazards in the United States. The paper, entitled "Spatial Patterns of Natural Hazards Mortality in the United States" by Borden and Cutter is in pre-print form but can be downloaded as a PDF here. First up, lets be clear that the authors are reputable - Susan Cutter in particular has made a massive contribution to our understanding of the social impacts of natural hazards and, unlike many working in this field, she has managed to keep her materials sensible, balanced and approachable.

The paper looks at the spatial pattern of mortality from hazards using an improved dataset orginally based upon the Spatial Hazard Event and Loss Database (SHELDUS), which is available at http://sheldus.org), covering the period 1970-2004. Much of the paper relates to the reliability of the data and the quality of the database, but there are also some interesting outcomes in terms of the spatial distribution and also the cause of death.

First, the spatial distribution is perhaps not what one would expect (Fig. 1). Intuitively one might say that the highest level of mortailty would be on the west coast given the earthquake hazard, but in fact the map shows no clear spatial pattern, with pockets of high mortality occurring across the whole of the country. There is a slighlty higher level of mortality in the midwest than in the east, reflecting the pattern if temperature extremes perhaps.

Figure 1: The map of the spatial distribution of mortality across the USA for the period 1970-2004. This map is Fig. 3 from Borden and Cutter (2009) (Biomed Central Ltd).

The reason for this is that there is a vast range of causes of death in natural hazards in the USA, with temperature-related deaths (either from heat or cold) dominating.

So what of landslides? Well, the combined datasets indicate 170 landslide fatalities out of a total of 19,958, which is 0.85% of the total. In comparison, geophysical hazards (presumably earthquakes and volcanoes) provide 302 deaths (1.5% of the total).

One of the things that the study highlights, although does not really discuss explicitly, the key importance of time in such a study, bearing in mind the low frequency but high magnitude nature of natural hazards. For instance, the time period does not include the occurrence of Hurricane Mitch in 2005 - I suspect that the map might look a little different if the >1800 fatalities in this event were included. Similarly, the map does not include a very large earthquake in California or on the Cascadia subduction zone. Therefore, great care must be taken in the use of such data to evaluate risk rather than impact.

The paper finishes by acknowledging that much work is needed on this type of analysis. The paper presented here is a very useful step along the way.

Reference
Borden, K.A. and Cutter, S.L. 2008 in press. Spatial Patterns of Natural Hazards Mortality in the United States. International Journal of Health Geographics, 7:64. doi:10.1186/1476-072X-7-64 .

November 2008 fatal landslide maps

So here are the scores on the doors for fatal landslides in 2008. First the statistics:
Number of fatal landslides: 48
Number of fatalities: 396.

This is the map of the fatal landslides themselves (click on the map for a better view):

As is normal for this time of year the spatial dsitribution is quite scattered, with slides occurring in SE. Asia, S. Asia and C./S. America. This year there has been a particular focus in Colombia and in Brazil - in fact the map does not really show that there were multiple landslides in a small area (Santa Catarina) in S. Brazil that have resulted in >100 fatalities.

This is the map for the year to date:

Note the line of landslides running from NNE to SSW in China. Does it remind you of the aftershock map for the Wenchuan earthquake?