Drivers of natural disaster risk-reduction actions and their temporal dynamics: Insights from surveys during an imminent hurricane threat and its aftermath.

To improve preparedness for natural disasters, it is imperative to understand the factors that enable individual risk-reduction actions. This study offers such insights using innovative real-time (N = 871) and repeated (N = 255) surveys of a sample of coastal residents in Florida regarding flood preparations and their drivers during an imminent threat posed by Hurricane Dorian and its aftermath. Compared with commonly employed cross-sectional surveys, our methodology better represents relationships between preparedness actions undertaken during the disaster threat and their drivers derived from an extended version of Protection Motivation Theory (PMT). The repeated survey allows for examining temporal dynamics in these drivers. Our results confirm the importance of coping appraisals and show that risk perceptions relate more strongly to emergency protection decisions made during the period of the disaster threat than to decisions made well before. Moreover, we find that several personal characteristics that we add to the standard PMT framework significantly relate to undertaking preparedness actions, especially locus of control and social norms. Significant changes in key explanatory variables occur following the disaster threat, including a decline in risk perception, a potential learning effect in coping appraisals, and a decline in risk aversion. Our results confirm the advantage of the real-time and repeated survey approach in understanding both short- and long-term disaster preparedness actions.

US tropical cyclone flood risk: Storm surge versus freshwater.

Despite persistent record-breaking flood losses from tropical cyclones (TCs), the United States continues to be inadequately prepared for TC flood events, with the deficiency in residential flood insurance being a prime representation of this. One way to address this is through a better quantification of TC flood risk including variations associated with freshwater versus storm surge flood hazard and damage. We analyze actual residential flood claim data from the National Flood Insurance Program (NFIP) for the full set of all 28 significant US landfalling TC-related flood events from 2001 to 2014 which we split by storm surge and freshwater. We illustrate key differences between the numbers of claims, paid claim amounts, and damage for freshwater and surge claims, as well as evaluate differences associated with flood zone, state, TC event, and flood depth. Despite the typical focus on surge TC flooding, freshwater flooding accounts for over 60% of TC paid claim and damage amounts. Surge flooding often occurs outside of high-velocity flood zones, which is not reflected in the NFIP premiums. Statistical analysis indicates that depth-damage ratios vary significantly by surge versus freshwater and by geography. State-level analysis shows that land-use policies and building codes likely affect differences in damage along with storm characteristics and geography. The findings highlight the need to mitigate and manage both freshwater and surge TC flood risk and for more individualized flood insurance premiums less tied to flood zone. It appears that the latter need may be addressed by the Federal Emergency Management Agency (FEMA)'s Risk Rating 2.0.

Identifying Promising Messages to Increase Hurricane Mitigation Among Coastal Homeowners in the United States.

Hurricanes threaten the physical and financial well-being of coastal residents throughout the United States. Though hurricane-related losses are largely avoidable through property mitigation (e.g., structural modifications to existing homes), few homeowners invest in mitigation. Communication campaigns, which have influenced risk-related behaviors in other domains, hold promise for persuading coastal residents to engage in hurricane mitigation. The development of successful campaign messages relies, in part, on formative research to assess the potential influence of candidate message strategies. We present results from mixed-methods, theory-driven research to identify promising beliefs for persuading homeowners in coastal/coastal-adjacent regions of Alabama and Florida to install a high wind-resistant (HWR) roof. In Study 1, we elicited homeowners' (n = 74) salient behavioral, normative, and control beliefs about installing an HWR roof. Using established procedures, we content analyzed open-ended responses and categorized them by thematic content. In Study 2, we surveyed another sample of homeowners (n = 533) to examine the extent to which salient beliefs/themes about installing an HWR roof (elicited in Study 1) are promising targets for a communication campaign, given their associations with homeowners' intentions to retrofit. Results demonstrate that across elicited beliefs, common themes include the protection and property resilience reroofing affords, and anticipated expenses and financial barriers associated with reroofing. The most promising beliefs include behavioral beliefs that installing an HWR roof will protect oneself and one's family, and normative beliefs about the likelihood that one's family and community will install an HWR roof. We discuss the implications of findings for the development of hurricane mitigation messaging.

Adoption of Individual Flood Damage Mitigation Measures in New York City: An Extension of Protection Motivation Theory.

This study offers insights into factors of influence on the implementation of flood damage mitigation measures by more than 1,000 homeowners who live in flood-prone areas in New York City. Our theoretical basis for explaining flood preparedness decisions is protection motivation theory, which we extend using a variety of other variables that can have an important influence on individual decision making under risk, such as risk attitudes, time preferences, social norms, trust, and local flood risk management policies. Our results in relation to our main hypothesis are as follows. Individuals who live in high flood risk zones take more flood-proofing measures in their home than individuals in low-risk zones, which suggests the former group has a high threat appraisal. With regard to coping appraisal variables, we find that a high response efficacy and a high self-efficacy play an important role in taking flood damage mitigation measures, while perceived response cost does not. In addition, a variety of behavioral characteristics influence individual decisions to flood-proof homes, such as risk attitudes, time preferences, and private values of being well prepared for flooding. Investments in elevating one's home are mainly influenced by building code regulations and are negatively related with expectations of receiving federal disaster relief. We discuss a variety of policy recommendations to improve individual flood preparedness decisions, including incentives for risk reduction through flood insurance, and communication campaigns focused on coping appraisals and informing people about flood risk they face over long time horizons.

Tornado Damage Mitigation: Homeowner Support for Enhanced Building Codes in Oklahoma.

Tornadoes impose enormous costs on society. Relatively simple and inexpensive enhancements to building codes may reduce these costs by 30% or more, but only one city in the United States has adopted these codes. Why is this the case? This analysis addresses this question by examining homeowner support for more stringent building codes in Oklahoma, a conservative state that routinely experiences damaging tornadoes. Survey data show that support for mandatory mitigation policies like building codes is subject to countervailing forces. Push dynamics, including objective risk data, homeowners' risk perceptions, and damage experience, encourage support for mitigation. Pull dynamics, such as individualistic and conservative worldviews, and skepticism about climate change, generate opposition. At the margin, the pull dynamics appear to exert more force than push dynamics, creating only a weak basis of support that is not strong enough to overcome the status quo bias in a state that is cautious about regulatory measures. The concluding section offers suggestions for changing these dynamics.

Quantifying riverine and storm-surge flood risk by single-family residence: application to Texas.

The development of catastrophe models in recent years allows for assessment of the flood hazard much more effectively than when the federally run National Flood Insurance Program (NFIP) was created in 1968. We propose and then demonstrate a methodological approach to determine pure premiums based on the entire distribution of possible flood events. We apply hazard, exposure, and vulnerability analyses to a sample of 300,000 single-family residences in two counties in Texas (Travis and Galveston) using state-of-the-art flood catastrophe models. Even in zones of similar flood risk classification by FEMA there is substantial variation in exposure between coastal and inland flood risk. For instance, homes in the designated moderate-risk X500/B zones in Galveston are exposed to a flood risk on average 2.5 times greater than residences in X500/B zones in Travis. The results also show very similar average annual loss (corrected for exposure) for a number of residences despite their being in different FEMA flood zones. We also find significant storm-surge exposure outside of the FEMA designated storm-surge risk zones. Taken together these findings highlight the importance of a microanalysis of flood exposure. The process of aggregating risk at a flood zone level-as currently undertaken by FEMA-provides a false sense of uniformity. As our analysis indicates, the technology to delineate the flood risks exists today.

Individual hurricane evacuation intentions during the COVID-19 pandemic: insights for risk communication and emergency management policies.

The U.S. 2020 hurricane season was extraordinary because of a record number of named storms coinciding with the COVID-19 pandemic. This study draws lessons on how individual hurricane preparedness is influenced by the additional risk stemming from a pandemic, which turns out to be a combination of perceptions of flood and pandemic risks that have opposite effects on preparedness behavior. We conducted a survey in early June 2020 of 600 respondents in flood-prone areas in Florida to obtain insights into households' risk perceptions and preparedness for the upcoming hurricane season under COVID-19. The results show that concerns over COVID-19 dominated flood risk perceptions and negatively impacted people's evacuation intentions. Whereas hotel costs were the main obstacle to evacuating during Hurricane Dorian in 2019 in the same geographic study area, the main evacuation obstacle identified in the 2020 hurricane season is COVID-19. Our statistical analyses investigating the factors influencing evacuation intentions show that older individuals are less likely to evacuate under a voluntary order, because they are more concerned about the consequences of becoming infected by COVID-19. We observe similar findings based on a real-time survey we conducted in Florida with another group of respondents under the threat of Hurricane Eta at the end of the hurricane season in November 2020. We discuss the implications of our findings for risk communication and emergency management policies that aim to improve hurricane preparedness when dealing with additional health risks such as a pandemic, a situation that may be exacerbated under the future climate. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11069-021-05064-2.

Differences in the dynamics of community disaster resilience across the globe.

The consideration of disaster resilience as a multidimensional concept provides a viable and promising way forward for reducing risk and minimizing impacts today and in the future. What is missing is the understanding of the actual dynamics of resilience over time based on empirical evidence. This empirical understanding requires a consistent measure of resilience. To that end, a Technical Resilience Grading Standard for community flood resilience, was applied in a longitudinal study from 2016 to 2018 in 68 communities across the globe. We analyse the dynamics of disaster resilience using an advanced boosted regression tree modelling framework. The main outcome of our analysis is twofold: first, we found empirical evidence that the dynamics of resilience build on a typology of communities and that different community clusters experience different dynamics; and second, the dynamics of resilience follows transitional behaviour rather than a linear or continuous process. These are empirical insights that can provide ways forward, theoretically as well as practically, in the understanding of resilience as well as in regard to effective policy guidance to enhance disaster resilience.

Economic impacts of urban flooding in South Florida: Potential consequences of managing groundwater to prevent salt water intrusion.

High-value urban zones in coastal South Florida are considered particularly vulnerable to salt water intrusion into the groundwater-based, public water supplies caused by sea level rise (SLR) in combination with the low topography, existing high water table, and permeable karst substrate. Managers in the region closely regulate water depths in the extensive South Florida canal network to control closely coupled groundwater levels and thereby reduce the risk of saltwater intrusion into the karst aquifer. Potential SLR adaptation strategies developed by local managers suggest canal and groundwater levels may have to be increased over time to prevent the increased salt water intrusion risk to groundwater resources. However, higher canal and groundwater levels cause the loss of unsaturated zone storage and lead to an increased risk of inland flooding when the recharge from rainfall exceeds the capacity of the unsaturated zone to absorb it and the water table reaches the surface. Consequently, higher canal and groundwater levels are also associated with increased risk of economic losses, especially during the annual wet seasons. To help water managers and urban planners in this region better understand this trade-off, this study models the relationships between flood insurance claims and groundwater levels in Miami-Dade County. Via regression analyses, we relate the incurred number of monthly flood claims in 16 Miami-Dade County watersheds to monthly groundwater levels over the period from 1996 to 2010. We utilize these estimated statistical relationships to further illustrate various monthly flood loss scenarios that could plausibly result, thereby providing an economic quantification of a "too much water" trade-off. Importantly, this understanding is the first of its kind in South Florida and is exceedingly useful for regional-scale hydro-economic optimization models analyzing trade-offs associated with high water levels.

A hydro-economic model of South Florida water resources system.

South Florida's water infrastructure and ecosystems are under pressure from socio-economic growth. Understanding the region's water resources management tradeoffs is essential for developing effective adaptation strategies to cope with emerging challenges such as climate change and sea level rise, which are expected to affect many other regions in the future. We describe a network-based hydro-economic optimization model of the system to investigate the tradeoffs, incorporating the economic value of water in urban and agricultural sectors and economic damages due to urban flooding while also accounting for water supply to sustain fragile ecosystems such as the Everglades and coastal estuaries. Results illustrate that maintaining high reliability of urban water supply under scenarios of reduced water availability (i.e., drier climate conditions) may trigger economic losses to the Everglades Agricultural Area, which will likely become more vulnerable as competition over scarce water resources increases. More pronounced economic losses are expected in urban and agricultural areas when flows to the Everglades are prioritized. Flow targets for coastal estuaries are occasionally exceeded under optimal flow allocations to various demand nodes, indicating that additional storage may be needed to maintain the environmental integrity of the estuarine ecosystems. Wetter climate conditions, on the other hand, generally lead to increased flows throughout the system with positive effects on meeting water demands, although flood mitigation efforts will necessitate additional releases to the estuaries. Strengths and limitations of the hydro-economic model are discussed.

Assessing Current and Future Freshwater Flood Risk from North Atlantic Tropical Cyclones via Insurance Claims.

The most recent decades have witnessed record breaking losses associated with U.S. landfalling tropical cyclones (TCs). Flood-related damages represent a large portion of these losses, and although storm surge is typically the main focus in the media and of warnings, much of the TC flood losses are instead freshwater-driven, often extending far inland from the landfall locations. Despite this actuality, knowledge of TC freshwater flood risk is still limited. Here we provide for the first time a comprehensive assessment of the TC freshwater flood risk from the full set of all significant flood events associated with U.S. landfalling TCs from 2001 to 2014. We find that the areas impacted by freshwater flooding are nearly equally divided between coastal and inland areas. We determine the statistical relationship between physical hazard and residential economic impact at a community level for the entire country. These results allow us to assess the potential future changes in TC freshwater flood risk due to changing climate pattern and urbanization in a more heavily populated U.S. Findings have important implications for flood risk management, insurance and resilience.