RAPID: Recording Tsunami Impacts from the Taan Fjord, Alaska Landslide of October 17th, 2015

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On October 17th, 2015, the largest landslide in North America in decades occurred in Taan Fjord, an arm of southeast Alaska's Icy Bay. The landslide triggered an enormous local tsunami. Flow indicators from satellite imagery suggest that the maximum tsunami runup immediately adjacent to the slide mass exceeds 190 m. Such a maximum runup would be second only to that created by the 1958 Lituya Bay landslide, a poorly recorded (by modern standards) event that is nonetheless the most important dataset for understanding extreme landslide tsunami hazards available to the engineering community. This project supports an interdisciplinary, coastal impact investigation of the tsunami generated by the Taan Fjord landslide. The aim of survey is to record runup measurements and tsunami impacts throughout Taan Fjord and Icy Bay. In the context of hazard mitigation, a record of the tsunami behavior is of paramount importance, and would assist in resolving many questions, for example: How far away from potential landslides does infrastructure need to be located How close can liquefied natural gas (LNG) facilities, as are being proposed throughout western Canada and Alaska, be to landslide sources What about the hazard to existing marinas, harbors, and ports, and the many cruise ships that regularly travel through fjord systems The data to be recorded will be essential to the proper specification of the landslide source and its tsunamigenic potential.From preliminary simulations and early reconnaissance trips, we expect there to be widespread areas where the tsunami runup exceeds 100 meters in elevation, with a gradual, but very localized attenuation of wave height as the tsunami traveled through and out of Taan Fjord. Owing to the extreme runup and inundation distances, as well as the remote location, the team will use a high-accuracy Real Time Kinematic (RTK) survey system, which we expect will yield 10-cm accuracy location elevations, after the data is tide-corrected. The types of data to be collected include the most-important runup elevations, flow depth profiles, areas of sediment scour and deposition, debris piles, and the impact of the tsunami on various types of vegetation. The data from this survey, once processed, will be provided freely to all members of the engineering community. In particular, Lynett's involvement with tsunami hazard mapping in western States, his participation in the National Tsunami Hazard Mitigation Program (NTHMP), and existing collaborations with others studying landslide tsunamis indicates that this data will be folded into ongoing hazard studies immediately.