Climate Crisis Increases Dangers from Mudslides

Mudflows form when a steep slope made of loose material becomes "oversaturated" with water, explains Glade: "Then the forces that have so far held it on the slope are suddenly no longer sufficient." Due to gravity, stones, debris, and soil suddenly start moving. "A typical mudflow consists of 50 to 70 percent solid material, and the remaining 30 to 50 percent is water," he explained: There are so-called channelized mudflows, which occur in the bed of a torrent, and slope mudflows, which do not follow a clearly defined path.

Climate crisis leads to unprecedented mudflow dimensions

As with floods, there are mudflows of different magnitudes, which have so far occurred on average every hundred, five hundred, or thousand years, according to the expert. Due to the climate crisis, these periods are likely to shorten significantly. "Thus, people must expect events in strengths and dimensions that have not been experienced in recent years," explained Glade: "This naturally poses great challenges for all stakeholders, including residents, authorities, geological services, and early warning centers."

In Austria, due to the previous glaciation of the Alps, there is a lot of available sediment material (depositional material, note) for mudflows on the slopes, said the researcher: "In other regions, this is not the case, and larger mudflows will not occur even with increased extreme rainfall." Debris and sediment can therefore occur here until the slopes are virtually cleared of sediment. "This state has of course not yet been reached," said Glade: "We are rather at the beginning of developments that will continue in the coming years and decades."

Dangers from mudflows: Spatial planning and protective structures must be reviewed and improved

Accordingly, one must "actively and concretely deal with" the danger. This includes better scientific research into the processes that lead to the formation of mudflows and reviewing spatial planning for potential revision as a preventive measure. "It is also necessary to check whether the dimensions of technical protective structures are still sufficient for the things we can expect in the future," explained Glade.

In principle, according to the geomorphologist, it is even possible to predict the probability of mudflows. One can, on the one hand, map where there is enough sediment material on the slope for this. Secondly, it is possible to estimate threshold values from past events, at which rainfall amounts and intensities the debris is likely to rush down the valley. "The conditions on which the stability of the slopes depends are constantly changing," he said: "With every mudflow and landslide that occurs, the stability state of the slope system changes." For example, with a forest clearing, you suddenly have different basic conditions. "This makes prediction very challenging," said the researcher.

(APA/Red)

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