Following on from last month's post about disaster risk reduction in Nepal, the BBC reports today of the threat of flooding in the Himalayas if earthquakes cause glacial lakes to rupture. As glaciers have melted, and continue to melt, they form lakes. In the event of an earthquake, the large ground accelerations result in these lakes bursting and causing considerable damage to property and infrastructure, as well as loss of life. Further problems can be caused when landslides (including seismically induced landslides) result in large amounts of material falling into lakes and causing them to burst.
This situation is an excellent example of a trigger mechanism (earthquakes, causing landslides, causing flooding) typically occurring in many areas affected by multiple hazards. In areas such as these a separate risk assessment for flooding, a separate risk assessment for landslides and a separate risk assessment for earthquakes will not adequately describe the risk in the area. It would be very easy to underestimate the vulnerability of people, and thus to conclude that the magnitude of risk is much lower than in the real case. Multi-hazard risk assessments would be a much more appropriate tool to understand the complex interaction of hazards in the Himalayan region. These take into account hazards triggering others, vulnerability being increased as a result of one hazard and the cumulative impact of multiple hazards. They try to give a much more 'real-life' view of the natural environment. Multi-hazard research is in a very young stage, yet it is very important and could greatly assist in disaster risk reduction programmes.