A catastrophic flash flood has struck northern Nepal on the Tibetan border, killing at least 157 people and leaving hundreds missing, including at least 34 Australians. The death toll is expected to rise.

Foreign tourists are among those feared dead or missing. Nepal’s tourism ministry reported 403 tourists unaccounted for, including 341 foreign nationals.

Footage shows torrents of mud and debris sweeping through settlements and carrying buildings and vehicles with them.

Early evidence suggests this was not an ordinary rain-driven flash flood, but what disaster science describes as a “cascading event”. So what do we know so far?

Not an ordinary flood

Investigators are examining a chain of events high in the Himalayas where one natural hazard seems to have triggered another.

Such phenomena are known as “cascading hazards” – chain reactions where an initial event directly triggers a sequence of subsequent events, often creating a much larger disaster.

Climate change is known to be driving faster glacier melt in the Hindu Kush Himalaya region, but scientists say it is too soon to pinpoint its role in these floods.

We know the flooding struck the steep, fast-flowing Bhotekoshi river system near Nepal’s border with Tibet........

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