Catching up - recent landslide events

The next few posts will be an attempt to catch up on the things that I missed whilst on vacation in Switzerland last week.  Thanks to the many people who have tipped me off about landslide events.  I will cover Pakistan in another post.


1. A large flow in Austria
Thanks to Martin Springer for highlighting this one.  On Saturday 21st August a severe storm triggered a 100,000 cubic metre flow in the Karwendel Nature Reserve.  Fortunately no-one was killed, but a dozen cars are trapped in a car park.  It will take two months to clear the debris.  There is a short video of the deposit and further details about the landslide (in German) here.

Read more by clicking below:



2. The power of a mudflow illustrated by an articulated truck in California
Thanks to Lisa Denke for this one.  A large storm in eastern California on Thursday last week triggered a mudflow in the Owens Valley in eastern California.  An articulated truck (known as a tractor trailer in the US) was caught in the path.  There is a short but useful video of the event in this news report:



3.An excavator in Gilgit-Baltistan
Accompanying the video above is an extraordinary image of the aftermath of the rains in Pakistan, courtesy of the Pamir Times:

I am reminded of the old "how does the driver of a snowplough get to work?" line.


4. Devastating landslides in Turkey
Also on Thursday last week, heavy rainfall triggered landslides in the town of Gundogdu, in Rize Province in Turkey, killing 12 people.  The image below is taken from this news report:

5. The typhoon season has now got started
Finally, the very slow start to the Pacific typhoon season has now come to an end, with a series of storms developing at the moment.  The three storms currently active all have the potential to cause landslides (image from Tropical Storm Risk):

Lionrock and Namthuen could both bring very heavy rainfall to southern China as they track inland over the next couple of days.  Meanwhile, the forecast track of Typhoon Kompasu suggests that this very intense typhoon could bring substantial amounts of rainfall to the Korean peninsular.  North Korean in particular is very vulnerable to the effects of heavy rainfall due to the extensive deforestation endemic in that country.  The potential impacts of this storm are serious, although note that there is considerable uncertainty in track forecasts.

The low level of NH hurricanes and typhoons in summer 2009

One of the reasons that the northern hemisphere summer is essentially the global landslide season is that landfalling tropical cyclones (typhoons and hurricanes) represent a rather efficient way of triggering slope failures. This is especially the case in the Caribbean, Taiwan, Japan, SE and S China, the Philippines and Vietnam. Typhoon rain is astonishing to experience for the first time - peak intensities of 100 mm per hour are not unusual in the largest events. The hourly rainfall data below is for the passage across Korea of Typhoon Rusa in 2002, taken from Lee and Choi (2007):

Note that at Gangneung the peak hourly precipitation was 100.5 mm (4 inches) and the peak 24 hour rainfall was 870.5 mm (35 inches). It is unsurprising that such events cause landslides on a large-scale.

The northern hemisphere tropical cyclone season is primarily associated with warm sea surface temperatures, and hence runs primarily through the summer and early autumn months. Interestingly, and for reasons that are far from clear, the energy associated with northern hemisphere tropical cyclones has been reducing for a number of years. Ryan Maue at Florida State University runs a superb web page that tracks tropical cyclone occurrence globally. He has the following graph of global and northern hemisphere tropical cyclone energy (note smoothed using 24 month running sums):

Levels of tropical cyclone activity are now approaching a 50 year low. However, even by recent standards the level of Northern Hemisphere tropical cyclone activity to date this season has been exceptionally low. Ryan also provides the following graph of Northern Hemisphere tropical cyclone energy (ACE) for the first three months of each season since 1979:

It is not for me to speculate on why tropical cyclone activity should be at such a low level (Ryan is much better qualified to do so), but it is clear that so far the Northern Hemisphere tropical cyclone occurrence has been a damp squib. The occurrence of landslides reflects this (I will post my monthly update in the next few days). This is of course good news in terms of landslides and floods, but it is bad news for farmers who rely on rainfall for irrigation, the hydro-electric industry in these areas, and many others whose livelihood and.or welfare depends upon water derived from tropical cyclones.

It will be interesting to see whether level of activity dramatically increase later in the season.

Meanwhile, the S. Asian monsoon remains very weak, with the Indian Meteorological Department noting that total precipitation in the monsoon season is 19% below the long term average. Again, the occurrence of fatal landslides that I have recorded is mirroring this pattern. Meanwhile, much of China is suffering from unusually intense monsoon rains. For example, Shanghai has just suffered its heaviest rainfall for 70 years.