The findings of the research by the School of Earth and Ocean Sciences, published in the journal Scientific Reports, is challenging theories that are currently espoused suggesting that landslide activity could increase proportionally with increased rainfall. According to the research, a 10% increase in the frequency of rainstorms is projected by climate change experts, would only increase shallow landslide frequency by less than 0.5%.
Shallow landslides are often caused by heavy rainfall and occur because the soil collapses, resulting in fast moving debris flows of mud and rocks, which can prove to be very hazardous to anything in their path.
Findings from this latest research show that landslides are more commonly triggered by the build-up of colluvium (soil) on steep hillslopes, as opposed to rainfall from storms. Usually, soil slowly accumulates on a mountainside over anything from thousands to tens of thousands of years, which is then carried downhill during a storm, causing a landslide.
It then takes another couple of thousand years for the soil to accumulate on the mountainside again, which means that an increase in the frequency of storms would have minimal effect on the frequency of landslides during this time.
“Our results have shown that lots more storms result in very few extra landslides. Though observations tell us that heavy rainfall triggers landslides, it is the process of soil accumulation that happens in the thousands of years leading up to a landslide that can be really important in determining how often landslides occur. Though we still expect shallow landslides to continue to be a major hazard in our future wetter climate, we do not expect the frequency of landslides to increase in proportion to the frequency of extreme precipitation events,” stated Lead author of the study, Dr Rob Parker, from Cardiff University’s School of Earth and Ocean Sciences.
Landslides pose a direct hazard to both life and infrastructure, and can also negatively affect the drinking water in the area as well as water for agriculture, which can lead to major health problems.