Remarkable NASA imagery of catastrophic flooding around Manchhar Lake in Pakistan

NASA have provided the most dramatic evidence yet of the catastrophic floods that are occurring around Manchhar (Manchar) Lake in Pakistan (see my post yesterday on this issue).  This image was captured by the ALI instrument on 18th September:

Compare this with an image taken of the same area just three days earlier:

Or the Google Earth image of the same area, which was collected in May this year:

Geo-TV, an independent TV station in Pakistan, reports that some of the breaches that are causing these floods are now 1 km wide, whilst NTDTV notes that the number of people displaced by this most recent component of the floods may be as high as 250,000. 


The breaches have allowed the water level in the main body of the lake to fall slightly, bringing some relief elsewhere, but with new areas continuing to experience flooding that is not cause for much overall cheer.

Mars Odyssey image of landslide

Although landslides on other planets have not been a major theme of this blog, there is an interesting area of science that focuses on these intriguing phenomena. Of course a great deal of this research is quite difficult given our poor knowledge of the conditions on and in the slopes when they occur. The availability of increasingly high resolution imagery is however helping in the understanding of these features. There is a hope that we might understand terrestrial landslides better if we can see how slides operate in other environments, although to date I must admit that I am unconvinced that this has really happened.

Yesterday NASA released the image below, which shows an area of Mars with a quite interesting landslide. It was collected by Mars Odyssey THEMIS (acknowledgement to NASA/JPL/Arizona State University):

Fig 1: Mars Odyssey THEMIS (acknowledgement to NASA/JPL/Arizona State University) image showing a landslide on Mars.

At first the landslide might not be obvious, but look closely on the centre right side - it is clear that the slide is a ridge failure with a reasonably long run-out. I have zoomed into the image to show the landslide below (Fig. 2):

Fig 2: Enlargement of Mars Odyssey THEMIS (acknowledgement to NASA/JPL/Arizona State University) image showing a landslide on Mars.

I have processed and annotated the image (Fig. 3) to highlight some key features. I think (though this is unconfirmed) that the landslide is about 2 km wide and 6 km long. Note that the presumably more resistant material that forms the ridge appears to be intact on the landslide body. The landslide has two smaller failures on its flank. Finally, it also appears to have a few small craters on it, which presumably means that it is not too recent (UPDATE: thanks to Dr Mauri McSaveney for pointing out that not too recent in this case probably means 2-3 billion years old).

Fig 3: Annotated enlargement of the Mars Odyssey THEMIS (acknowledgement to NASA/JPL/Arizona State University) image showing a landslide on Mars (Click on the image for a better view in a new window).

Similar landslides do occur on Earth. For example, Fig. 4 shows the Frank landslide, which I have described before. Note that in the Mars case the slipped block has only partially broken up, whilst at Frank it disintegrated completely to form a rapid flow. I am sure that there are better examples from Earth, but I cannot think of them at the moment. Can anyone come up with one?

Fig 4: Natural Resources Canada photograph of the Frank landslide, Turtle Mountain, Alberta, Canada.

TRMM and landslide monitoring

One of the most admirable science projects at NASA at the current time is an attempt to create a global landslide and flood warning system using the Tropical Rainfall Monitoring Mission satellite data. TRMM using a precipitation radar system to provide near real time data on the intensity of rainfall in the tropical and subtropical regions. NASA then make these data available on the TRMM website.

The usefulness of these data can be illustrated using the last seven days of rainfall in Asia. During this time the monsoon has strengthened - we are just moving into the real wet season in south and SE. Asia. Furthermore, the first really destructive tropical cyclone of the year has just tracked across the Philippines and then made a more-or-less direct hit on Hong Kong, before dissipating in southern China. As well as causing the sinking of a passenger ferry, this typhoon also deposited large volumes of rain that have been responsible for extensive landslides and floods. Using TRMM it is possible to obtain an estimate of the volume of rainfall that has fallen in Asia over the last week (Fig. 1). This does come with a caveat, which is that the spatial distribution of rainfall is very variable at the local scale, which this instrument does not resolve. Nonetheless it does provide a really interesting indication of the rainfall distribution.

Figure 1: TRMM image of the rainfall distribution for the seven days to 27th June 2008 at 06:00 UTC. Note the high rainfall totals for the Philippines and S. China, generated by the passage of Typhoon Fengshan (click on the image for a better view).

The locations of high rainfall appear to correlate with areas of flooding - for example, in this time floods were reported in the Central Philippines, South China around the Pearl River delta and in parts of N. India. Unfortunately, the correlation with fatal landslides at least is far poorer. Figure 2 shows the locations of fatal landslides that I have recorded in the same time period. A caveat is that perhaps not all the landslides in China have yet been reported, so the map in Figure 2 might change a little. However, it is clear that a simple rainfall total algorithm is not enough to provide a really good indication of the distribution of fatal landslides at least.

Figure 2: Locations of reported fatal landslides in the 7 day period shown in Figure 1.

The team at NASA are working hard on their landslide algorithm and are doing a terrific job. This is one of the most interesting landslide projects underway at the moment. I am hoping that they will present some interesting progress in this work at the International Symposium on Landslides and Engineered Slopes in China next week.