Natural Hazards Review

As the quantitative hazard research, particularly stemming from the engineering fields, aims to move from component- and building-level modeling into the interdisciplinary space of community-level modeling for resilience, the need to test, verify, and validate community resilience algorithms becomes a critical challenge; virtual testbeds are an effective tool for such purposes. We define a virtual testbed as an environment with enough supporting architecture and metadata to be representative of one or more systems such that the testbed can be used to design experiments, examine model or system integration, and test theories. Testbeds enable researchers to assess multidisciplinary integrated community resilience models, thereby helping decision makers to make better community hazard mitigation plans and recovery decisions. This paper leverages the current momentum on using virtual testbeds for community resilience analysis to dissect what testbeds are in practice. To obtain consensus on the presented definition of a testbed, the paper conducted a virtual survey with testbed experts. The survey primarily explored how testbeds have been used across different disciplines, how testbeds differ from case studies, and what are the minimum requirements for a testbed. The paper, then, presents findings from a systematic literature review on 22 identified existing community resilience testbeds and 103 associated publications. According to the literature review and survey results, community resilience testbeds should have both a hazard module and a community module that ideally includes physical, social, and economic systems. The literature review concludes with a discussion on the available tools for testbed development, typical challenges testbed developers encounter, and areas for future testbed research. The availability of existing testbeds for reuse by other researchers, standardization of the development and publication process of new testbeds including obtaining, cleaning, and validating the required data, and verification of numerical algorithms are the main detected issues that need to be addressed in future research.

Since the 1970s, the ongoing retreat of the global cryosphere has been affecting human societies and causing a series of snow- and ice-related disasters (SIRDs). Based on existing research results, this paper focuses on searching for the formation mechanism of SIRDs, classifies their types and spatiotemporal scales, and reveals the integrated impacts of the SIRD and its future situation on global high-hazard areas. On land, SIRDs mainly occur in the high mountainous areas of middle–low latitude and the permafrost regions of high latitude, in the behaviors of increasing frequency of glacier/snow/glacier lake outburst flood–related disasters and an expanding range of freeze–thaw disasters. The recorded frost events show a decreasing trend but the hail hazard distributions are greatly heterogenous. Overall, the frequency of rain-on-snow events is projected to increase on land in the future. In the ocean, SIRDs are mainly distributed in the Arctic coastal areas and global low-lying islands or areas, with great potential risk. Among them, coastal freeze–thaw, icebergs, and sea-level rise and its impacts are likely or expected to continue increasing in the next few decades.

Following a disaster, residents of a community may be displaced from their damaged homes, leading to expensive and lengthy disruption, with many choosing to move away permanently. Population losses may hinder recovery and exacerbate inequalities across neighborhoods. This study considered household place attachment and identified groups with low place attachment along with expensive and slow postdisaster recovery. We developed a framework to integrate place attachment considerations into housing recovery simulations. We used data from the American Housing Survey to develop housing and neighborhood satisfaction models and identify the neighborhoods with the least-attached residents. A computational simulation framework was used to simulate postearthquake housing recovery for a community and assess expected costs and time frames. We used the triad of low place attachment, high cost, and slow recovery to identify households prone to permanently moving away from their communities. A case study of housing recovery after a hypothetical earthquake near San Francisco demonstrated the application of the methodology. We found that about 10% of the population in some neighborhoods are prone to moving away after a large earthquake. Households with low income, renters, and those in older buildings are most likely to have low place attachment and experience costly and slow recovery. Whereas existing approaches rely on heuristics, the approach and results in this paper provide quantitative means to assess potential population losses and inform efforts to reduce them. The framework to integrate place attachment into housing recovery simulations is versatile and employs publicly available information making it transferable to other communities.

Modern structural design codes assume a statistically stationary climate. However, it is now known that the climate is changing at a rate that calls into question the stationarity assumption. This study was undertaken to explore various methods of accounting for climate nonstationarity. The geographical domain of this study covers most of Canada, intending to explore how best to update future climatic variables in the National Building Code of Canada (NBC). Outputs from future climate simulations for North America by Environment and Climate Change Canada (ECCC) and the Pacific Climate Impacts Consortium (PCIC) were used, focusing on a representative concentration pathway (RCP) scenario, namely the RCP8.5 emissions scenario. Surface hourly mean wind speeds and ground snow amounts were extracted from the simulations and used to detect and quantify trends in the extreme climatic variables from 1950 through 2100. This study reviewed different concepts for evaluating climatic design variables under stationary and nonstationary climates. It was found that within the range of linear nonstationarity detected for grid points within Canada, the results predicted using these nonstationary methods are close. Therefore, a simpler approach, namely Minimax design life level, was adopted to estimate the design wind speeds for $1/50$ and $1/500$ annual probability of exceedance and the design ground snow loads for $1/50$ and $1/\mathrm{1,000}$ annual probability of exceedance. Design values derived based on nonstationary approaches were compared with the results estimated using the conventional return period concept between 1986 and 2016 and a moving-time-window method between 2060 and 2090 centered at 2075.

Research shows that postcrisis policy change in democracies is shaped by how crises are framed. Given structural political differences, the role that such framing plays in postcrisis policy change in other types of political systems is unclear. Therefore, this study adjusts the concept of crisis framing to authoritarian China and subsequently identifies framing strategies used by national leaders in response to the severe acute respiratory syndrome (SARS), the Sichuan earthquake, and the 2009 H1N1 influenza pandemic. Based on qualitative thematic analysis of statements made by national leaders, this paper shows that although no framing contests existed between them, these individuals used different framing strategies in response to different crises, and each strategy corresponds with different degrees of crisis-induced policy change. We observed major policy changes when national leaders simultaneously acknowledged the crisis, admitted a malfunctioning status quo, and put forward explicit proposals for postcrisis policy changes. Conversely, we observed minor policy change when national leaders denied the significance of the crisis, blamed the crisis on external forces, or put forward no or only abstract proposals for policy change. We argue that national leaders in China use the former strategies if they want to legitimize major policy changes and use the latter if they want to defend the status quo and restrict policy change.

The intention of this study is to estimate the expected soil-building resonance phenomena of the Dhaka Metropolitan Development Plan (DMDP) area of Bangladesh during earthquakes. The target is to identify the effect of the geology of the shallow depth and the buildings situated on the ground above the DMDP area. The predominant frequency of the soil is obtained from the horizontal-to-vertical spectral ratio (HVR) analysis of microtremor observations. Similarly, longitudinal and crosswise principal vibrational frequencies of each building have been ascertained from the fast Fourier transform (FFT) of the observed microtremor measurements. When the principal vibrational period of the structure is near to the period of the nearby ground, building-soil resonance may occur. A rapid visual assessment (RVA) has been carried out for 3,252 educational institutes in the DMDP area and through the prioritization scheme, 611 buildings have been selected for preliminary engineering assessment (PEA). Some of these buildings will be later allowed to be either retrofitted or demolished based on the findings of this study. Out of those prioritized buildings, microtremor measurements have been performed on selected 114 buildings and nearby soil for which standard penetration test and seismic downhole test data are available. Also, microtremor observations at additional 500 free-field locations are available from a previous study. The period-number of story linear relationship, estimated from the 114 microtremor observations, allowed estimating the fundamental frequency for 3,252 buildings. The DMDP area symbolizes a significant example since the principal vibrational period for the majority of the structures is reasonably different from the predominant period of the nearby ground. Only around 4% of the structures demonstrate a significant likelihood that a building-soil resonance effect may take place, while around 96% are at a relatively low resonance stage.

The quantification of damage potential is an essential prerequisite for mitigating the impact of natural hazards on the built environment of a country. Catastrophe models are complex computer programs that allow us to measure damage potentials, investigate the possible effects of climate change, and more. Model-generated information, however, is highly sensitive to the incorporated assumptions, and thus the soundness of our knowledge of risk and the effectiveness of mitigation mechanisms is in direct proportion to how well we understand those assumptions. The history of the development of catastrophe modeling in the last 60 years has much to teach us about these and other important aspects. However, it has been underexamined. This paper aims to trace the origins of modern catastrophe modeling—identifying its roots and rapid progress from World War II until the mid-1960s, when risk assessment approaches grew from empirical data-dependent techniques to physics-based computer simulations, and from the 1960s to early 2000s, when catastrophe models acquired an important role in policy analysis. The role of Don G. Friedman, a scientist not yet properly recognized in the risk modeling community although arguably the chief pioneer of catastrophe modeling, is highlighted. The sources used to construct this account include relatively unexplored ones as well as interviews with key pioneers of catastrophe modeling.

Weeks after a disaster, crucial response and recovery decisions require information on the locations and scale of building damage. Geostatistical data integration methods estimate post-disaster damage by calibrating engineering forecasts or remote sensing-derived proxies with limited field measurements. These methods are meant to adapt to building damage and post-earthquake data sources that vary depending on location, but their performances across multiple locations have not yet been empirically evaluated. In this study, we evaluate the generalizability of data integration to various post-earthquake scenarios using damage data produced after four earthquakes: Haiti 2010, New Zealand 2011, Nepal 2015, and Italy 2016. Exhaustive surveys of true damage data were eventually collected for these events, which allowed us to evaluate the performance of data integration estimates of damage through multiple simulations representing a range of conditions of data availability after each earthquake. In all case study locations, we find that integrating forecasts or proxies of damage with field measurements results in a more accurate damage estimate than the current best practice of evaluating these input data separately. In cases when multiple damage data are not available, a map of shaking intensity can serve as the only covariate, though the addition of remote sensing-derived data can improve performance. Even when field measurements are clustered in a small area—a more realistic scenario for reconnaissance teams—damage data integration outperforms alternative damage datasets. Overall, by evaluating damage data integration across contexts and under multiple conditions, we demonstrate how integration is a reliable approach that leverages all existing damage data sources to better reflect the damage observed on the ground. We close by recommending modeling and field surveying strategies to implement damage data integration in-real-time after future earthquakes.

Abstract

COVID-19 research conducted in the pre-vaccine era indicates strong hesitancy toward vaccination among African Americans. Recent research has found growing acceptance of COVID-19 vaccination in the general US population. This study investigated vaccination intentions in Black communities and explored behavioral mechanisms involved in vaccination decisions. It focused on individuals’ risk perception in the face of a double hazard relating to the coronavirus disease and the vaccine. Using data from a national survey of 547 African Americans in January 2021, the results demonstrate considerable lingering vaccine hesitancy among African Americans. A survey experiment applied fear appeals to raise risk perceptions of threats from (1) the coronavirus, (2) the COVID-19 vaccine, or (3) both the disease and the vaccine. The findings show null effects of the treatments on individuals’ intentions to get a vaccine. However, when incorporating efficacy beliefs about the COVID-19 vaccine, the analysis found a positive effect of perceived vaccine efficacy on vaccination intentions. The study concludes that future research and practice need to replace fear appeals with efficacy-raising regimes, and identifies strategies that can be adopted in communicating and engaging with Black communities to promote COVID-19 vaccination.

Practical Applications

Amid the COVID-19 pandemic and other prolonged crises, it is critical for public authorities to remain flexible and to time managerial and policy interventions with shifting public demands and emotions at distinct phases of the crisis cycle. In the later stages, fear appeals need to be replaced with efficacy-raising regimes to counter negative emotions and capitalize on people’s yearning for significant changes. Risk communication should empathize with the concerned individuals, avoid direct efforts to correct misinformation, highlight the benefits of COVID-19 vaccination, and tailor messages to specific subpopulations. Community engagement needs to occur on a variety of channels to reach people where they are, and should identify and mobilize trusted individuals in the target communities.

During intense rainfall, shallow landslides often occur on natural slopes due to the rising groundwater level. This study proposed a simple model for rainfall-induced shallow landslide prediction in broad areas based on an infinite homogeneous slope assumption and a simplified hydrological process. For this purpose, a numerical model, TAG_FLOW, was developed in Fortran 90. Its structure was divided into four modules: (1) a surface infiltration module based on the Green-Ampt model, (2) a groundwater-level simulation based on a previously developed simple one-dimensional vertical prediction method combined with horizontal groundwater distribution, (3) a surface water control module based on two-dimensional shallow water equations and a depression removal process, and (4) slope stability estimated using the assumption of an infinite homogeneous slope. The simplified hydrological process for the surface and subsurface flows was validated using a tilted V-catchment model and tested with the Abdul and Gillham system. For the performance evaluation of TAG_FLOW, we applied the model to analyze rainfall-induced landslides for an area in North Kyushu during the historically large torrential rainfall event in July 2017. The landslide prediction capacity of the TAG_FLOW model was evaluated by the TRIGRS model and the actual landslide map. The results confirmed that both groundwater and surface water contributed to the occurrence of landslides in the study area. The prediction performance of the TAG_FLOW model was slightly better than that of the TRIGRS model, but both models overpredicted landslides in the study area.

The 2015 Gorkha earthquake was one of the most devastating earthquakes in Nepal in this century. Postdisaster reconstruction is a complex and highly challenging process, especially concerning developing countries like Nepal, as it involves several well-coordinated plans and working activities. Due to the large scale of devastation, the Nepal government created a separate body, the National Reconstruction Authority (NRA), to manage and oversee recovery and reconstruction activities. This paper briefly discusses organizations typically involved in postdisaster reconstruction processes and the multifaceted roles they play. Document analysis on research papers, collected reports from the NRA, governmental departments, and many other organizations involved in the reconstruction was carried out. This study provides a comprehensive review of the reconstruction process after the 2015 Gorkha, Nepal, earthquake, whereas previous studies have covered a specific issue. The reconstruction works are presented structurally in detail. Similarly, the crucial steps and lesson learned for managing expectations and building back better are highlighted. This study may help to develop effective organization and policies in future postdisaster reconstruction.

Bridge failure is mostly caused by geotechnical failure. Because caissons are the automatic choice for foundation systems for marine structures, such as bridges and wind turbines, this study addresses the determination of seismic passive earth pressure coefficients for caissons. In the present study, a realistic three-dimensional (3D) failure wedge was assumed to be formed behind caissons of different widths on the basis of the past results of experimental and numerical studies. The limit equilibrium method of analysis was adopted to determine the seismic passive earth pressure coefficients due to the cohesion component, surcharge component, and unit weight component. The current study takes into account the relative width and depth of the geotechnical structure and returns a series of design charts and tables for different soil-soil friction angles, soil-wall friction angles, and horizontal and vertical seismic acceleration coefficients. The results were compared with previous experimental and theoretical studies and found to be in excellent agreement.

Abstract

This paper describes hazard mitigation grants management activities undertaken by governors, an area that remains understudied. Governors play important roles in other grants management activities, and these actions have the potential to improve hazard mitigation shortcomings. Findings were derived from two projects: (1) a national survey of State Hazard Mitigation Officers (SHMOs) that explored their perceptions of the role of governors in the implementation of federal hazard mitigation programs and policies, and (2) semistructured interviews with individuals who were involved in the implementation of innovative local hazard mitigation grant programs. SHMO survey responses indicate limited engagement in several activities related to FEMA Hazard Mitigation Assistance (HMA) grants. The results of the semistructured interviews show that some governors play important roles in hazard mitigation grants management activities, including facilitating partnerships and governance strategies, guiding state hazard mitigation priorities, and negotiating and securing hazard mitigation funding. Further research is needed to understand why governors assume active or passive roles in hazard mitigation grants management activities.

Practical Applications

It is important to understand the hazard mitigation grants management activities undertaken by governors, because their actions have the potential to improve risk reduction efforts across the US, an issue that remains understudied. Information gathered during this study drew from two projects, including a national survey of State Hazard Mitigation Officers, who administer FEMA Hazard Mitigation Assistance (HMA) grants, and personal interviews conducted with those who implemented innovative local hazard mitigation grant programs. Key grants management issues explored included reviewing hazard mitigation policies, setting HMA priorities and approving hazard mitigation plans, attending state agency meetings, and briefing legislators and members of Congress. The results of the survey showed that most governors played a limited role in hazard mitigation grants management, whereas interviews suggest that some governors played important roles in facilitating hazard mitigation partnerships, guiding state hazard mitigation priorities, and negotiating and securing non-federal hazard mitigation funding. The combined findings suggest that the active or passive roles assumed by governors may further the disparities across states regarding their ability to manage HMA grants effectively.

This study presents a model-based framework to assess the time-varying accessibility of a roadway network on a system-wide level during extreme flood events. A regional MIKE 21 hydrodynamic model consisting of 1,912,576 computational points with mesh cell resolutions ranging from 70 to 15 m is utilized to compute regional inundation during an extreme 500-year flood scenario. This approach allows for an explicit accounting of the impact of pluvial flooding on roadway network accessibility. Accessibility conditioned on flood depth is then computed using a raster approximation of the roadway network model employing the flood-fill search method. The approach is demonstrated in the flood-prone low-gradient region of Lafayette, Louisiana, which experienced a devastating flood event in August 2016. The findings suggest that the main evacuation points enjoy a greater degree of accessibility compared to medical facilities within the urban core of the city during the flood peak. Significant improvements in network accessibility can be made by targeted mitigation of specifically flood-prone roadway segments. However, the analysis demonstrates the adverse impacts of such mitigation activities in low-gradient urban floodplain systems when implementing routine drainage compensation steps. The approach provides key insights into the role played by pluvial flooding and flood duration on network accessibility and can help inform emergency response and transportation systems planning and design efforts.

With recent hurricanes causing devastating economic losses, structural damages, and societal impacts on coastal communities, residential building hurricane mitigation measures have gained increasing attention. However, retrofits are often costly and therefore beget inherent tradeoffs. In particular, the balancing of the postdisaster losses against upfront mitigation costs remains a constant challenge for community resilience planning. Existing mitigation optimization frameworks on the community scale have primarily focused on seismic hazards and typically have weak integration of the structural damages with the socioeconomic impacts. In the present study, finite element modeling of the residential buildings is applied to better incorporate the structural damages under combined wind and wave loadings. A multiobjective linear constrained optimization framework for improved residential building hurricane retrofit is developed to balance the structural damages, home displacements, morbidities, net direct economic losses, and initial mitigation expenditures under hurricane threats. For the present analysis, the mitigation actions of building elevation and improved construction practices are simulated. The framework is tested in a case study for an existing coastal community under 50-, 100- and 500-year hurricane events considering community-specific socioeconomic factors. The generalized pattern search algorithm is selected to determine the Pareto-optimal solutions. The results indicate large potential reductions in social, structural, and economic losses under optimized mitigation, but tradeoffs exist if the mitigation technique is found to be cost-ineffective, such as in the case of the improved construction practices. The findings highlight the importance of informed decision-making and home retrofits in improving community resilience.

Abstract

The purpose of this study was to assess the role played by the International Training Course, given by the Center for the Study of Active Volcanoes (CSAV) at the University of Hawai’i at Hilo, in the development of human resources for volcano observatory staff around the world. The study design included a literature review, interviews with representatives from 10 national volcano observatories, and electronic surveys designed and conducted by Florida International University, targeting graduates of training courses sponsored by the Volcano Disaster Assistance Program (VDAP), a cooperative partnership between the US Agency for International Development (USAID) and the US Geological Survey (USGS). The knowledge, attitude, and practice (KAP) method was used to develop a survey and a composite KAP index. Of the 92 individuals who answered the survey, 47 had completed the CSAV course. Two groups were formed from the survey respondents: (1) 47 people who were CSAV graduates; and (2) 45 people who did not take CSAV training. An independent samples $t$ test and a one-way multivariate analysis were conducted to compare the KAP index and the three subindices. The heads of the volcano observatories identified the CSAV International Training as one of the most useful educational offerings relevant to volcano observatory operations available worldwide. The statistical analysis showed significant differences in the KAP index, knowledge subindex, and practice subindex between the two study groups. Results indicate that CSAV graduates are in a better position to attain self-sufficiency in studying and monitoring volcanoes, and by doing so, contribute more effectively to mitigation efforts for volcanic unrest and eruptions.

Practical Applications

The purpose of this study was to assess the role played by the International Training Course by the Center for the Study of Active Volcanoes (ITC-CSAV), held at the University of Hawai’i at Hilo, in the development of human resources for volcano observatory staff around the world. The study included: (1) interviews conducted with 10 heads of national volcano observatories from Latin American and South Asian countries, and (2) an electronic survey, based on the knowledge, attitude, and practice (KAP) method, targeting graduates of different training courses sponsored worldwide by the US Volcano Disaster Assistance Program (VDAP). The heads of volcano observatories identified the ITC-CSAV as one of the most useful educational offerings relevant to volcano observatory operations available worldwide. The survey’s statistical analysis showed better KAP scores for the ITC-CSAV graduates than for the non-ITC-CSAV graduates. The study concludes that ITC-CSAV graduates are in a better position to attain self-sufficiency in studying and monitoring volcanoes, and by doing so, contribute more effectively to mitigation efforts for volcanic unrest and eruptions. The KAP method was useful to assess knowledge, attitude, and practice of a group of professionals trained in aspects of volcano study and monitoring, and who voluntarily underwent this evaluation.

This study examines household preparedness for volcanic eruptions of Kīlauea and Mauna Loa in Hawai‘i. Specifically, correlation and regression analyses were conducted to test which variables (i.e., demographics, risk perception, hazard intrusiveness, affective response, hazard agent characteristics, risk area, and community bondedness) have significant effects on two measures of hazard adjustment (i.e., household emergency preparedness and perceived stakeholder preparedness). Regression results showed that community bondedness, household income (i.e., one of the demographics), and risk area predicted household emergency preparedness. In addition, community bondedness and risk area predicted perceived stakeholder preparedness. These results indicate that future research should include more detailed examinations of people’s hazard adjustments, the psychological reactions that motivate those hazard adjustments, and the antecedents of those psychological reactions. Finally, the data revealed that Kīlauea and Mauna Loa respondents had, on average, low levels of risk perception and hazard intrusiveness, so it is important for local emergency managers to increase residents’ volcano hazard awareness and preparedness for future volcanic threats.

Motivating investment in predisaster mitigation requires accurate estimates of natural hazard risks. The present tools for loss estimation overlook building-level variations in wind loading induced by the configuration of surrounding buildings, called neighborhood texture. In doing so, such tools underestimate expected wind-related losses and undervalue wind mitigation. In this paper, texture effects are incorporated into a widely recognized loss estimation framework and applied to a case study of the residential building stock in Florida, with a focus on five densely populated counties representing a range of hazard exposures. For this study, each building is individually assessed for its prevailing local texture, and its occupancy and building characteristics are probabilistically assigned based on current census data. Mitigation measures considered include shutters, straps, and tie downs. Even accounting for more than a third of homes already having these mitigation measures, the model results suggest that implementing them would yield annualized benefits of $4.3 billion statewide ranging from $136 per household in Duval County to $1,950 per household in Miami-Dade County (respectively 100% and 90% higher than conventional estimates).

Following the devastating Typhoon Haiyan, a project initiated by the Philippine government, known as Road Heightening and Tide Embankment (RHTE), was constructed to protect the coastal communities of the Leyte region in the Philippines against future storm surges. This research focuses on this newly built structure, which was investigated for coastal flooding and wave overtopping against extreme waves. Experimental and numerical modeling were conducted to simulate wave-structure interaction under different water level conditions. A $1:30$ scale representative geometry of the tide embankment was set up inside a wave flume containing a scaled beach profile representing areas beyond the No-Build Zone mandated by the government. Dam-break wave flow was used to generate turbulent bores similar to that of a storm surge. For the numerical model, SolidWorks and ANSYS CFX version 17.1 software were used. The multiphase Volume of Fluid (VOF) method was used to track the free surface of the fluid flow and was shown to be an accurate tool for numerical validation, as the maximum wave height distributions in the presence of the structure using both methods were in close agreement with one another, but the numerical results overestimated the wave heights. The final design of the tide embankment with a return wall was modeled using ANSYS CFX. Experimental and numerical models generated wave heights that were higher than Typhoon Haiyan with inundation heights of 6 to 9 m above mean sea level (MSL) approaching the structure while the inland wave height was approximately 2 to 4 m above MSL. Results of the experiment also showed that the presence of the structure reduced the water level by 1 to 5 cm (about 0.3 to 1.5 m in actual scale). Moreover, the presence of a return wall will reduce the inland inundation height between 0.1 and 0.5 m above MSL.

Tornadoes are violent, short-lived wind phenomena that may result in catastrophic damage to homes and property and significant fatalities. Based on statistical data, a majority of tornado-induced fatalities are related to building failures. As such, it is important to investigate damage and failure modes of buildings under tornado loadings to properly design tornado-resistant buildings. In this study, a literature review was conducted on recent tornado postevent damage surveys to identify representative failure modes of buildings under tornadoes. In addition, based on the direct observations and through analyzing the reconnaissance survey data collected from the Jefferson City, Missouri, tornado of May 22, 2019, different overarching damage types are presented with inferences behind the cause for each damage type and possible retrofits to improve building performance under tornadoes. The obtained research findings will enrich the knowledge base for tornado-resistant design, which will eventually improve the safety and welfare of individuals living in tornado-prone areas.

We examined the resale prices of 217 recently sold California single-family dwellings built before 1960 to determine whether buyers value seismic retrofit. Of these, sellers indicated that 29 houses had been seismically retrofitted: 17 pre-1940 houses (when unanchored foundations and unbraced cripple walls were common) and 12 built between 1940 and 1959 (when unbraced cripple walls were common). A stepwise regression analysis indicates that in 2020 California home buyers paid 17% more for retrofitted pre-1940 houses. Buyers may have paid about 1% more for retrofitted 1940–1959 houses, but the correlation is weak. A higher resale price is a powerful incentive for people to invest in foundation bolts and cripple wall bracing. It reinforces findings by other researchers that natural hazard mitigation not only saves (by avoiding future losses), but it also pays (through higher resale value).

Abstract

This paper introduces an approach to evaluate the performance of a previously implemented or proposed hurricane evacuation plan that describes where and when official evacuation orders are issued. The approach involves use of the new integrated scenario-based evacuation (ISE) decision support tool to define a best track evacuation plan as a reference point and measure the performance of other plans in relation to that according to their ability to meet multiple stated objectives: minimizing risk to the population, travel time, and time people are away from their homes. Using North Carolina in Hurricane Florence (2018) as a case study, we demonstrate the process by evaluating performance of both the actual set of orders as executed and the orders that would have been recommended if the new ISE decision support tool had been used during the event. All three plans were evaluated for two cases—assuming the hurricane unfolds as it actually did, and if the hurricane had instead evolved like one of 21 other realistic scenarios. Results suggest the actual evacuation was quite good, and the ISE tool could have resulted in improved evacuation performance.

Practical Applications

This paper introduces a comprehensive, replicable approach to evaluating the performance of a previously implemented or proposed hurricane evacuation plan (i.e., a plan that describes where and when official evacuation orders are issued). Currently, there is no formal way to do so. The method presented defines as a reference point the evacuation plan that would minimize the stated aims if there was no uncertainty in the hurricane behavior, that is, if we had a crystal ball so that at the time the hurricane formed we could know the eventual track, intensity, and associated wind, rain, and flooding hazards exactly. The approach then measures the performance of other plans in relation to that reference, with performance based on their ability to meet multiple objectives: minimizing risk to the population, travel time, and time people are away from their homes. This new method can be of practical use to (1) provide after-the-fact evaluation of past evacuations to facilitate learning, (2) support planning through comparison of alternative strategies and decision support tools for hypothetical future hurricanes, and (3) gauge expectations about what performance can be reasonably expected in different circumstances.