By Kirsty MacLeod
A five-fold increase in landslide events in the UK is due to heavy rainfall, say experts from the British Geological Survey and the Transport Research Laboratory.
Speaking today at the British Science Festival, Dr Helen Reeves and Dr Mike Winter linked the unusually high rainfall experienced across the country in 2012 - the wettest year since records began – to a leap in the incidence of landslides recorded by the British Geological Survey’s Landslide Response Team. One hundred and seventy-six landslides were recorded last year, causing a total of four fatalities – the first deaths related to landslides since 2006, when the Landslide Response Team began monitoring the press for information on local landslide events.
Dr Helen Reeves of the British Geological Survey says they are moving towards the “holy grail” – the ability to forecast landslide events at a regional and local level. The susceptibility of a slope to landslides is largely determined by rainfall, which increases the volume of water in the slope. When this reaches a level where the weight of the water is too much for the soil and rock to hold, gravity takes over, and the rocks and earth fall. A better understanding of the link between landslides and rainfall patterns will eventually allow the British Geological Survey to link weather forecasting with the likelihood of landslides occurring, with important implications for public safety.
Dr Mike Winter, Head of Ground Engineering at the Transport Research Laboratory, says that it is too soon to determine whether there is a link between the increase in landslide events and climate change. Patterns, however, seem to be emerging. In Scotland, for example, the average rainfall per year has remained more or less the same – but the patterns of how this rain is falling are different. There are now more storms during which rain falls with increased intensity over a shorter duration, more likely, says Winter, to trigger landslides.
An increase in landslide events inevitably also increases the risk of damage to transport and other infrastructure, with costly implications. Both Reeves and Winter say that it is difficult, however, to quantify or predict the economic impacts of landslide events. Damage associated with landslides in 2012 was substantial, and expensive. A debris-flow landslide on the busy A83 Rest and Be Thankful pass in Argyll caused road closures that cost the local economy £50,000 a day; a permanent engineering solution could cost upwards of £500million.
While the frequency of bad weather and landslides are increasing, so too is the use of an unlikely tool – Twitter. Reeves says that the British Geological Survey, now tweeting at @BGSLandslides, are increasingly able to take advantage of social media to find reports of landslides that might otherwise have gone unreported. The fast flow of information also means that they know about events faster than ever before. “Hopefully this information will help us break new ground,” says Winter. “Excuse the pun.”