Natural disasters in mountain landscapes, such as landslides, rock-ice avalanches and glacial lake outburst floods, are examples of catastrophic sediment-rich flows (SRFs). Whilst flood waters can cause damage, sediment rich flows can choke channels, moving car and house sized boulders down mountain river channels. They are expected to become more frequent due to global warming and they often have the greatest effect on vulnerable communities and assets in the least developed countries.
SRFs are often composed of vast quantities of sediment, which may blanket valley floors to depths of tens of metres. After the initial event, the subsequent re-working and transport of these sediments by rivers can generate large-scale waves of sediment or 'superslugs', which are a so-called 'legacy' impact of an SRF. These superslugs can affect:
- flood risk – for example by altering the river bed elevation of an existing channel
- infrastructure – for example by scouring bridge footings and damaging hydropower turbines
- water quality – for example, reducing water and energy security.
Such legacy impacts are poorly understood, and improving our understanding of these impacts is of vital importance if strategies are to be introduced.