FEMA initiated this project in September 2004 with a contract to the Applied Technology Council. The project was undertaken to address the need for guidance on how to build a structure that would be capable of resisting the extreme forces of both a tsunami and an earthquake. This question was driven by the fact that there are many communities along our nation's west coast that are located on narrow spits of land and are vulnerable to a tsunami triggered by an earthquake on the Cascadia subduction zone, which could potentially generate a tsunami of 20 feet in elevation or more within 20 minutes. Given their location, it would be impossible to evacuate these communities in time, which could result in a significant loss of life. Many coastal communities subject to tsunami located in other parts of the country also have the same potential problem. In these cases, the only feasible alternative is vertical evacuation, using specially design, constructed and designated structures built to resist both tsunami and earthquake loads. The significance of this issue came into sharp relief with the December 26, 2004 Sumatra earthquake and Indian Ocean tsunami. While this event resulted in a tremendous loss of life, this would have been even worse had not many people been able to take shelter in multi-story reinforced concrete buildings. Without realizing it, these survivors were among the first to demonstrate the concept of vertical evacuation from a tsunami. This publication presents the following information: General information on the tsunami hazard and its history; Guidance on determining the tsunami hazard, including the need for tsunami depth and velocity on a site-specific basis; Different options for vertical evacuation from tsunamis; Determining tsunami and earthquake loads and structural design criteria necessary to address them; and, Structural design concepts and other considerations. In September 2004 the Applied Technology Council (ATC) was awarded a “Seismic and Multi-Hazard Technical Guidance Development and Support” contract (HSFEHQ-04-D-0641) by the Federal Emergency Management Agency (FEMA) to conduct a variety of tasks, including the development of design guidance for special facilities for vertical evacuation from tsunamis, which ATC designated the ATC-64 Project. The effort was co-funded by FEMA and the National Oceanic and Atmospheric Administration (NOAA). The developmental process involved a variety of activities including review of relevant research and state-of-the-practice documentation and literature, preparation of technical guidance and approaches for tsunami-resistant design, identification of relevant tsunami loads and applicable design criteria, development of methods to calculate tsunami loading, and identification of desired architectural and structural system attributes for vertical evacuation facilities. The resulting guidance for design of special facilities for vertical evacuation from tsunami, as presented herein, addresses a range of relevant issues. Chapter 1 defines the scope and limitations of the guidance. Chapter 2 provides background information on tsunami effects and their potential impacts on buildings in coastal communities. Chapters 3 through 7 provide design guidance on characterization of tsunami hazard, choosing between various options for vertical evacuation structures, locating and sizing vertical evacuation structures, estimation of tsunami load effects, structural design criteria, and design concepts and other considerations. The document concludes with a series of appendices that provide supplemental information, including examples of vertical evacuation structures from Japan, example tsunami load calculations, a community design example, development of impact load equations, and background on maximum flow velocity and momentum flux in the tsunami runup zone.

This publication was equally funded by the National Oceanic and Atmospheric Administration (NOAA), which leads the National Tsunami Hazard Mitigation Program (NTHMP) and by the Federal Emergency Management Agency (FEMA), which is responsible for the implementation portion of the National Earthquake Hazard Reduction Program (NEHRP). This project was originally undertaken to address the need for guidance on how to build a structure that would be capable of resisting the extreme forces of both a tsunami and an earthquake. This question was driven by the fact that there are many communities along our nation's west coast that are vulnerable to a tsunami triggered by an earthquake on the Cascadia subduction zone, which could potentially generate a tsunami of 20 feet in elevation or more within 20 minutes. Given their location, it would be impossible to evacuate these communities in time, which could result in a significant loss of life. This issue came into sharp relief with the December 26, 2004 Sumatra earthquake and Indian Ocean tsunami. While this event resulted in a tremendous loss of life, this would have been even worse had not many people been able to take shelter in multi-story reinforced concrete buildings. Without realizing it, these survivors were among the first to demonstrate the concept of vertical evacuation from a tsunami. Many coastal communities subject to tsunami located in other parts of the country also have the same issue. In these cases, the only feasible alternative is vertical evacuation, using specially designed, constructed and designated structures built to resist both tsunami and earthquake loads. The design of such structures was the focus of the earlier work on this project, which resulted in the FEMA publication, Guidelines for Design of Structures for Vertical Evacuation from Tsunamis (FEMA P646). This is a companion publication intended to present information on how vertical evacuation design guidance can be used and encouraged at the state and local level. It is meant to help state and local government officials and interested citizens by providing them with the information they would need to address the tsunami hazard in their community, to help determine if vertical evacuation is an option they should consider, and if so, how to fund, design and build such a refuge.

Tsunamis have the potential to inflict severe damage and loss of life in coastal communities. Structures known as vertical evacuation buildings provide an alternative evacuation site for communities living in relatively flat, coastal regions with inadequate sources of high ground for evacuation. Design of these structures balances risk and economy, and requires both technical and social design considerations. The design must be ductile enough to resist seismic vibrations and also strong enough to resist static and hydrodynamic loads and impact forces from floating debris. Uncertainties in the tsunami wave characterization and force determination promote over-conservative designs which may be cost-prohibitive to build. Previous to the March 11, 2011 earthquake and tsunami in Japan, well-engineered reinforced concrete structures were thought to withstand tsunamis; however, in the 2011 event, many engineered reinforced concrete buildings failed as the tsunami forces were greater than anticipated. In order to properly determine the forces on a structure, the tsunami waves must be adequately characterized; this process is called the Tsunami Hazard Analysis. The key factors used to characterize tsunamis are identified and their imbedded uncertainties are discussed. The Tsunami Hazard Analysis can provide a range of precision in its output values and therefore a tiered approach to the Tsunami Structural Analysis that follows the Tsunami Hazard Analysis is proposed. In the Tsunami Structural Analysis, the velocity and height parameters characterize the tsunami and are used to determine the actual forces on a structure. Three tiers have been provided based on the information available for the site based on the tsunami hazard assessment: Tier 1 includes only runup elevation or height parameters of the tsunami inundation. Tier 2 includes detailed depth and velocity information provided from a numerical model of the area. Tier 3 includes a time series of depth and velocity information and may use a fluid-structure interaction numerical model to determine the forces directly. The first two tiers can be found in various forms in existing guidelines. The third tier is recommended for important facilities such as tsunami vertical evacuation buildings. The existing methodologies in the guidelines for the design of Vertical Evacuation Buildings, such as FEMA P-646, are reviewed. Their advantages, uncertainties, and limitations in the context of the discussions on Tsunami Hazard Assessment and Tsunami Structural Analysis are discussed. Based on the findings of this research, a tiered design rationale is proposed in order to clearly categorize uncertainties in the force estimation process. In addition to the rationale, main conclusions of this research include: (1) tsunami parameter clarification, including assumptions/applicability of different depth, velocity, added mass coefficients, among other parameters; (2) identification of need for flow parameter (h2u2)[subscript max] for computing overturning moments with reduced uncertainty; (3) building shape effects, for example U-shaped building coefficients need to be developed for the estimation of drag force and also in the determination of realistic and governing tsunami force combinations; and (4) identification and applicability of critical flow conditions as well as appropriate force combinations. The four topics above are important to mitigate risk in the design of vertical tsunami evacuation buildings and to promote economical designs that are feasible for many communities.