Flash floods in Nepal may be the result of a complex chain of hazards, including landslides, avalanches, and glacial lake outburst floods, rather than solely heavy rainfall. This complexity makes early warning systems particularly challenging, according to Professor Liz Stephens, Professor in Climate Risks and Resilience at the University of Reading.
Initial reports from Nepal indicate that an earthquake occurred around the same time as a landslide or avalanche, which then reportedly led to catastrophic flooding. Professor Stephens explained that in steep mountain valleys, a landslide can block a river, causing water to accumulate behind it. If this natural dam then fails, it can result in a sudden and devastating release of water and sediment downstream.