These Guide Specifications were developed as part of a Transportation Pooled Fund Study, TPF-5(307), that included the states of Alaska, California, Hawaii, Oregon, and Washington, as well as the Federal Highway Administration, and was led by Oregon. Reports of the Pooled Fund Study 5(307) have been published by ODOT (Lynett et al., 2021; Istrati and Buckle, 2021a, 2021b). The impetus for this project, and the development of these Guide Specifications, is twofold: recent damaging tsunamis such as the Japanese earthquake and tsunami of 2011 and the Indonesian tsunami of 2004 which demonstrated the potential damaging power of tsunamis, and the growing realization of the hazard posed by a potential Cascadia Subduction Zone event to a substantial portion of the west coast of the United States, as well as the hazard posed by more distant seismic events.

The December 26, 2004 Indonesian tsunami and the March, 2011 Japanese tsunami included a 70-m broken bore (i.e., wave), significant overland flows, and debris accumulation in the flow which all affected the performance of bridges. These tragedies, among others, provided graphic examples of the dangers posed by tsunamis, and the potential failure mechanisms that need to be addressed.