| Session Details | |
| Section | SS - Special Sessions |
| Session Title | Cascading hazards |
| Main Convener | Dr. Gerald Bawden (National Aeronautics and Space Administration (NASA), United States) |
| Co-convener(s) | Dr. Jack A. Kaye (National Aeronautics and Space Administration (NASA), United States) |
| Session Description | Extreme hazard events may trigger a series of cascading hazards that can collectively pose a greater societal risk than the initial source event. Extreme hazards are infrequent, significant events often impacting a large geographic area (hundreds of square kilometers), have global implications, and/or have broad societal impact. The associated cascading hazards collectively have a similar scale or may be more significant than the initial trigger. A few examples include the 1991 eruption of Mount Pinatubo that injected an estimated 20 million tons of sulfur dioxide and ash particles into the stratosphere, influencing atmospheric chemistry and climate for years. The eruption, in combination with monsoons and a typhoon that coincidentally followed, killed hundreds of people, sent ash, lahars, and mudflows across the landscape and into the ocean, thereby decimating regional ecosystems, rendering cropland unusable, killing corals, significantly impacting the fisheries, and altering watersheds. Another set of examples is the major woodland fires in the Western U.S. throughout the past two decades that have burned and sometimes reburned hundreds of thousands hectares. Following the fires, the denuded landscapes have an elevated time-varied susceptibility for fluvial driven hazards such as debris flow, landslides, flooding, and other dynamic topographic/fluvial hazards that often extended well beyond the boundaries of the initial burn area. A final example is the 2015 Gorkha earthquake in Nepal, which triggered over 3,500 landslides and avalanches in the Himalayas, many of them either partially or completely damming rivers in the valleys below, resulting in localized flooding and the potential risk of debris dam failures. Monsoon rainfall following the earthquake sequence triggered additional river crossing landslides and other mass wasting events, thereby putting communities upstream and downstream at an elevated risk. This session will focus on the understanding the relationships, interdependencies, preconditioning parameters, triggering thresholds, and tipping points among fluvial/meteorological and solid Earth hazards. |