Flood is the most impactful natural disaster in the U.S. and continues to cause significant damage and losses (Doocy et al., 2013). Despite a suggestion that new development within the 100-year flood zone [i.e., special flood hazard area (SFHA; Al Assi et al., 2023a)] decreased nationwide (but with widely varying trends across space) between 2001 and 2011, an estimated 25.3 million people in the U.S. resided within the 100-year flood zone in 2011 (Qiang et al., 2017). Currently, average annual loss (AAL; Rahim et al., 2022a) is $13.2 and $19.1 billion within and outside the SFHA, respectively, and is projected to rise by 33.8% ($17.6 billion) and 21.2% ($23.1 billion) by 2050, respectively (Wing et al., 2022). The susceptible population faces increasing exposure to damage and losses from anticipated sea level rise and increased flood frequency and intensity due to the effects of climate change (Lin and Shullman, 2017; Xian et al., 2017).

To reduce flood risk in flood-prone areas, it is critical and urgent to provide optimized adaptation and mitigation strategies to vulnerable residents (Dewan, 2013). Previous studies indicate that adopting flood risk mitigation strategies is a sound financial investment with a benefit-cost ratio (BCR) of 5:1 when exceeding relevant provisions of model building codes (Multihazard Mitigation Council, 2017). One of the most effective and feasible approaches is raising the first-floor elevation (FFE). This additional height above the base flood elevation (BFE) is known as freeboard (Sharp, 2018; van Duin et al., 2021).

Even though the benefits of installing freeboard have been identified broadly, implementation has been hindered, in part because the lack of quantified financial benefits in relation to cost has dampened public demand for this mitigation practice. The evaluation process requires consideration of the many economic aspects that vary by environment and individually-customized requirements for each building project. However, such a comprehensive approach has rarely been available to the public, particularly for flood-prone communities. Even in the absence of such detailed information, the need for providing stakeholders and practitioners with the best actionable information available for more robust flood risk assessment requires advances in freeboard benefit estimates (Mostafiz et al., 2022a).

In addition, communication about the benefits of freeboard is hindered by the lack of a suitable web-based decision-making tool (to the best knowledge of the authors) that helps the public access freely and evaluate flexibly the customized levels and optimized financial benefits of freeboard. This concern is complicated by the fact that different users have distinct perspectives regarding the financial costs and benefits of freeboard. While tenants have little influence in decision-making regarding freeboard implementation as homeowners do, they play an indirect role in that they must take into consideration safety from the flood hazard when they choose their residence. Moreover, tenants are vulnerable to content-related flood losses. Landlords, by contrast, are generally immune to content-related flood losses but are vulnerable to building-related losses. Community leaders may be affected only indirectly by either type of loss but are likely to be most concerned about resilience at the neighborhood scale. Communications between the leaders and other resilience stakeholders are affected by their widely-ranging perceptions of the role of citizens in flood risk management (Wehn et al., 2015).

Several web portals provide decision-making tools that include flood risk, expected frequency of events, and management strategies, which are generally applicable to broad areas but fail to provide customized detailed financial benefits for the various stakeholders. Such portals may include static risk representation features that are not customizable to user-defined roles, preferences, and location and/or include jargon and contextual language that can be an obstacle for the public to understand and utilize. Moreover, the tone of the message in communicating risk seems to be important, as Poussin et al. (2014) found that encouragement via coping rather than discouragement via threats seem to have the better impact on flood mitigation behavior. Thus, an intuitive web-based, flood risk and freeboard decision-making portal with robust features for analyzing customized flood risk and freeboard financial benefits is needed to encourage homeowners, tenants, landlords, developers, insurance adjusters, community leaders, and other stakeholders to understand flood information easily and take needed action for flood mitigation promptly, at the individual building level (Mostafiz et al., 2022a). These barriers have continued to impede resilience to the flood hazard.

To ameliorate these identified gaps, the overarching goal of this study is to establish a web-based, decision-making system that suggests the most cost-efficient freeboard height for mitigating future flood risk to residential buildings for new construction. The proposed method is designed to estimate freeboard savings under various future scenarios by considering relevant variables including freeboard cost, flood risk, and insurance, with results freely and instantaneously available.

Quantification of flood risk by identifying the optimized mitigation measures and providing appropriate information to stakeholders is a fundamental baseline for flood risk management (De Risi et al., 2018). Benefit-cost analysis (BCA; Al Assi et al., 2023b) is a common method to identify the best choice between multiple options. It compares each option's expected financial benefits and cost with current “no-action” scenario (Zarekarizi et al., 2020). While the cost of adding freeboard is often modest, the lifetime savings on flood insurance premiums and the benefits of prevented flood losses, as revealed by life-cycle benefit-cost analysis (LCBCA), can be substantial (Gnan et al., 2022a). Other life-cycle benefits of freeboard implementation include reduced suffering, faster recovery, increased building value, and enhanced individual and/or community resilience (Gnan et al., 2022a). In addition, life is protected and rental cost during displacement is avoided (Xian et al., 2017). In terms of freeboard decision making processes, few studies focus on developing frameworks to estimate the optimal freeboard for single-family homes and analyze the home elevation decision (e.g., Xian et al., 2017; Zarekarizi et al., 2020). While these studies represent a significant step forward, they only considered either premium savings or flood reduction in their decision criteria. The inclusion of both flood reduction and premium savings allows for better evaluation of freeboard financial benefits (FEMA, 2008).

Previous studies and currently operational web portals collect and provide diverse flood-related information from/to the public. Li et al. (2006) implemented a web-based flood forecasting system (WFFS) for the Shuangpai region in China to help hydrologists and other engineers to make more-informed decisions. By using the WFFS, hydrologists in China can reduce the processing time by circumventing manual calculation in traditional flood forecasting, and the tool aims to reduce the data analysis and processing time for providing flood forecasting information rapidly. This tool also uses a real-time flow model and provides alternatives for authorized users, so decision makers can choose an ideal option by comparing their pros and cons. Holz et al. (2006) created a web-based flood management system for water level observation using artificial neural network (ANN) models. Users can explore a real-time web portal and receive SMS and email of flood warning from the system. The Victorian flood web portal, targeting the Victoria area in Australia, collects information about the demands and the possible benefits from potential users of their website based on telephone survey and provides relevant flood risk and mitigation information on the website before, during, and after a flood event (Molino, 2009). The Flood Information System (FIS) for the Somesul Mare area in Romania (Almoradie et al., 2013) supports the following three features: flood risk management (FRM) awareness, flood information, and public participation. The advantages of this tool include enhancement of flood risk management, reduced costs of process, and shared information among different stakeholders (Almoradie et al., 2013). Khalid and Ferreira (2020) generated a web-based, real-time, flood prediction tool for the Chesapeake Bay area. This tool is well-organized and designed to incorporate a variety of resources, such as wave level guidance systems, storm surge and wave prediction models, hydrodynamic models, extreme weather forecasts, and ensemble forecasts.

Several other websites show potential for providing flood risk data and mitigation strategies to flood-prone residents (Figure 1). Flood Factor (https://floodfactor.com/) is a free online website tool that helps Americans find past-to-future flood risk generated by the First Street Foundation. Using this tool, the public can acquire a variety of static information regarding generalized flood risk. Iowa Flood Information System (IFIS), created at the Iowa Flood Center (IFC) at the University of Iowa (https://ifis.iowafloodcenter.org/ifis/app/), is also a free, one-stop, online tool for providing community-based flood conditions, forecasts, inundation maps, and flood-related information. This website not only explains how to use the tool on the website using text and photos, but also provides a video guide to enhance the user's understanding of the tool. However, since this tool provides information on a broad and large area, there is a considerable limitation in that users cannot obtain detailed information customized to a specific area. Aqueduct Flood (https://www.wri.org/applications/aqueduct/floods/) is a free online data platform that helps governments, companies, and the public understand flood risk in coastal and riverine areas, and conducts a BCA of the flood protection investment. This tool provides important information including annual total cost vs. benefits, cumulative net benefits, cumulative maintenance costs, and evolution of flood protection. However, the portal does not output personalized information because it is designed to provide a community-level based analysis report. U.S. Flood Inundation Map Repository (USFIMR, https://sdml.ua.edu/usfimr/) and Global Flood Inundation Map Repository (GloFIMR, https://sdml.ua.edu/glofimr/) have been created at the University of Alabama to provide historical inundation extent maps. These portals also provide general historical flood information and inundation maps with interaction features with maps, but customized flood and adaptation information are not provided. In addition, various studies on flood monitoring have been conducted for large study areas such as countries (Limlahapun and Fukui, 2009), states (Sunkpho and Oottamakorn, 2011), rivers (Hagemeier-Klose and Wagner, 2009; Mure-Ravaud et al., 2016), and reservoirs (Ghobadi and Kaboli, 2020). However, to date, a product that facilitates the freeboard decision-making process at the individual building level has not yet been developed.

This section describes the developed features of the web-based decision-making tool and the detailed analyses of the customized report. In addition, case studies and their implementations are included to show the functionalities and implications of the developed web-based decision-making tool.

Individuals are often unaware of flood risk in their residential areas. A robust approach that allows them to quantify the expected losses and obtain actionable information while also considering the future flood hazard has been unavailable. Thus, several vulnerable communities remain unaware of the risk and lack the opportunity to enjoy the possible benefits of mitigation strategies such as elevation increase (Warren-Myers et al., 2018). Providing communities with flood risk information including possible mitigation strategies and the related financial impacts is imperative in informing the decision-making process and thus enhancing long-term resilience. Many homeowners, tenants, landlords, and other community stakeholders still have not been exposed to this vital risk information and flood adaptation approaches such as adding freeboard. In addition, corresponding benefits of taking mitigation measures have not been fully realized by homeowners, particularly in disaster-prone areas. A reliable tool that quantifies the expected financial benefits of adding freeboard in a way that communicates clear results and provides actionable information to stakeholders is needed.

This study provides a new approach for integrated estimation of a variety of economic aspects of freeboard installation. A new location-based method of assessing freeboard financial benefits and savings for improved flood risk mitigation and decision-making is proposed. Thus, the primary contribution of this study is in the combined approach that enables calculation of freeboard benefits and savings for an individual building with specific property and flood risk information. The inclusion of both flood reduction and insurance premium savings in the calculation procedure allows for comprehensive and customized evaluation of freeboard benefits for an individual property. In addition, the interactive web-based framework allows the public to explore individually-tailored flood risk and freeboard benefit information for residences. The web-based decision-making tool (floodsafehome.lsu.edu) provides actionable information to stakeholders such as homeowners, tenants, landlords, designers, builders, and planners without revealing private information. The tool analyzes possible freeboard alternatives, along with the expected cost and benefits. Users are provided with estimated construction costs, amortized costs per month, savings per month, and flood loss reduction, by entering only location information, the building area, and number of floors. The info-graphic output is designed to communicate information quickly and clearly to users.

The specific findings of the case study show that

Information regarding the optimal freeboard levels and associated benefits is expected to be vital to assist homeowners, tenants, landlords, and other stakeholders who promote community wellbeing. Minimizing the number of flooded homes, particularly repetitive-loss properties, saves homeowners from repeated heartache, moving expense, and inconvenience, and it also assists the community by circumventing a reputation that would decrease property values.

Despite the beneficial information produced from this decision-making system, several limitations that will be addressed in future research must be considered. First, the scope of implementation is limited, to date. More specifically, this study used static flood zone information to develop an approach, which was generated by FEMA on 16 February 2021. The back-end system database must be updated when FEMA updates the flood zone information. In addition, the methodology should be improved to incorporate FEMA's RISK Rating 2.0 flood insurance rating system (Rahim et al., 2023). Moreover, the calculations designed in this methodology only consider direct physical economic losses. Other relevant and possible losses such as displacement, disruption, and relocation are not currently included in the calculation. In Jefferson Parish, for example, flood depth grids at multiple return periods are available only for the areas within the levee-protected area. In St. Tammany and Terrebonne parishes, only flood depth data for the 100-year return period are available, and in some areas, even the 100-year depths are unavailable. Nevertheless, as data become more abundant, the back-end of the portal should be updated accordingly. The output and analyzed outcomes are dependent on the input data including the accuracy of the flood depth grid, flood zone, and user-input data. In addition, the proposed website currently does not incorporate future flood scenarios based on climate change. The consideration of future climate change is necessary to provide accurate flood risk and associated freeboard cost and benefits into the future. Furthermore, the social, psychological, and environmental benefits are not addressed in benefit evaluation due to various uncertainties and underlying limitations. Thus, the benefits of adding freeboard are considerably underestimated. Finally, technology can sometimes exclude rather than include some marginalized and vulnerable populations, so implementation of the tool is likely to be limited unless community members can make explicit efforts to communicate its message to those who may not be aware of it. Future work will focus on expanding the scalable and customizable approach for increased geographical coverage and for community-level decision making.

Since the proposed system is scalable and customizable, the authors will continually improve the system by addressing the limitations. In addition, the system will be expanded and updated periodically, for covering other areas of Louisiana and ultimately the flood-vulnerable homes and areas throughout the U.S. In addition, based on this decision-making system, the authors will establish a new feature for community-level decision making that supports estimating freeboard benefits and savings of multiple residences or subdivisions in order to assist community practitioners or contractors in identifying flood risk, cost-efficient freeboard levels, and savings for their communities.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

CF provided original ideas and advice on the overall project methodology and edited the text. Y-CL supervised the web-tool development and edited the initial text. RM collected and analyzed the data and edited the text. JL developed the front-end of the web-tool and developed the initial text. SM developed the back-end of the web-tool and edited the text. RR edited early and late drafts of the text. MR developed the code and edited the text. EG developed the initial text. MF helped to develop the original ideas of the web-tools. All authors contributed to the article and approved the submitted version.