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Freeboard—elevation of a structure above the base flood elevation (BFE)—is a critical component in mitigating or avoiding flood losses. However, the unrevealed benefits and savings of freeboard installation have prevented communities from adopting this approach. To improve decision-making for residents, prospective residents, and other stakeholders...
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The flood disaster of July 2021 claimed the lives of more than 220 people in Western and Central Europe – particularly severely affected was the Ahr Valley in Germany, where the floods caused at least 135 fatalities, damaged and destroyed more than 9,000 buildings, and caused billions of euros in damage. To prevent such a disaster from happening ag...
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... Evaluating flood risk involves assessing flood occurrence probability and its consequences. Previous studies have used AAL as an expression of annual flood risk (Al Assi et al. 2023b;Bowers et al. 2022;Friedland et al. 2023;Gnan et al. 2022a, b;Hallegatte et al. 2013;Mostafiz et al. 2022b), which takes into account the costs associated with the building itself and its contents, as well as indirect costs such as use risk during renovation (Al Assi et al. 2023a). The Gumbel distribution is commonly used for flood peak prediction and flood frequency analysis Parhi 2018;Patel 2020;Singh et al. 2018). ...
Special flood hazard areas (SFHAs), defined as having an annual probability of occurrence of 1 percent or above, are used by U.S. Federal Emergency Management Agency (FEMA) to demarcate areas within which flood insurance purchase is required to secure a mortgage. However, quantifying flood risk within SFHAs can be challenging due to the lack of modeled flood depth data for all return periods. To address this issue, this research quantifies flood risk indicated by average annual loss (AAL) within the A Zone—the subset of the SFHA where wave heights can potentially range from 0 to 3 feet. The methodology resolves the Gumbel quantile function for four distinct flooding cases (i.e., locations flooded at return periods exceeding 1.58-, 10-, 25-, and 50-year return period events) and generates synthetic flood hazard parameters for these cases within the 100-year floodplain, as well as with additional elevation above the base flood elevation (BFE), known as freeboard, for single-family homes with different attributes. The results indicate that for single-family homes in the A Zone, with the lowest floor elevated to the BFE, the AAL ranges from 0.3 to 1 percent of the building replacement cost value. Adding one foot of freeboard reduces flood risk by over 90% if the annual flood risk is between the minimum and 25th percentiles and the 100-year flood depth is less than two feet. The demonstrated approach helps enhance flood resilience in the A Zone, demonstrating the feasibility of proactive measures to protect communities.
Supplementary Information
The online version contains supplementary material available at 10.1007/s41742-024-00577-7.
... • Risk is the product of the probability of event occurrence and its consequences. Recent studied tend to quantify the average annual loss to represent the flood risk (Quinn et al., 2019;Gnan et al., 2022b,c;Mostafiz et al., 2022b;Rahim et al., 2022;Wing et al., 2022;Al Assi et al., 2023b,c;Friedland et al., 2023). Messner and Meyer (2006) emphasized the importance of spatial scale for flooding characteristics, differentiating macro-, meso-, and micro-scale approaches. ...
Much of the U.S. petrochemical infrastructure is heavily concentrated along the western coast of the Gulf of Mexico within the impact zone of major tropical cyclone events. Flood impacts of recent tropical disturbances have been exacerbated by an overall lack of recognition of the vulnerabilities to process systems from water intrusion, as well as insufficient disaster mitigation planning. Vulnerability assessment methods currently call for the aggregation of qualitative data to survey the susceptibility of industrial systems to floodwater damage. A means to quantify these consequences is less often employed, resulting in a poor translation of the threat of flood hazards to a crucial element of the economy. This paper reviews flood damage assessment for industrial facilities and presents a component-level conceptual methodology to assess the consequences of flood events. To more effectively communicate loss potential from flood events, the proposed methodology utilizes synthetic estimation to calculate repair requirements, shutdown time, and direct cost.
... Flood risk is assessed as the product of flood occurrence probability and the associated consequences (Šugareková & Zeleňáková, 2021). Average annual loss (AAL) has been used in past research to represent flood risk (Hallegatte et al., 2013;Armal et al., 2020;Rahim et al., 2021;Mostafiz et al., 2022a;Bowers et al., 2022;Wing et al., 2022;Yildirim & Demir, 2022;Al Assi et al., 2023b;Friedland et al., 2023) in terms of costs associated with direct building loss, direct contents loss, and indirect losses such as use loss while the building is being renovated (Al Assi et al., 2023a). AAL is calculated as the integral of flood loss as a known function of the flood probability (or flood return period), and the Gumbel distribution function is one of the most widely accepted probability functions (Singh et al., 2018;Patel, 2020). ...
Floods inflict significant damage even outside the 100-year floodplain. Thus, restricting flood risk analysis to the 100-year floodplain (Special Flood Hazard Area (SFHA) in the United States of America) is misleading. Flood risk outside the SFHA is often underestimated because of minimal flood-related insurance requirements and regulations and sparse flood depth data. This study proposes a systematic approach to predict flood risk for a single-family home using average annual loss (AAL) in the shaded X Zone–the area immediately outside the SFHA (i.e., the 500-year floodplain), which lies between the limits of the 1.0- and 0.2-percent annual flood probability. To further inform flood mitigation strategy, annual flood risk reduction with additional elevation above an initial first-floor height ( F F H 0 ) is estimated. The proposed approach generates synthetic flood parameters, quantifies AAL for a hypothetical slab-on–grade, single-family home with varying attributes and scenarios above the slab-on-grade elevation, and compares flood risk for two areas using the synthetic flood parameters vs existing spatial interpolation-estimated flood parameters. Results reveal a median AAL in the shaded X Zone of 0.13 and 0.17 percent of replacement cost value ( V R ) for a one-story, single-family home without and with basement, respectively, at F F H 0 and 500-year flood depth <1 foot. Elevating homes one and four feet above F F H 0 substantially mitigates this risk, generating savings of 0.07–0.18 and 0.09–0.23 percent of V R for a one-story, single-family home without and with basement, respectively. These results enhance understanding of flood risk and the benefits of elevating homes above F F H 0 in the shaded X Zone.
An accurate economic loss assessment for natural hazards is vital for planning, mitigation, and actuarial purposes. The widespread and costly nature of flood hazards, with the economically disadvantaged disproportionately victimized population, makes flood risk assessment particularly important. Here, flood risk is assessed as incurred by the homeowner vs. the flood insurer for insured U.S. properties through the derivation of average annual loss (AAL). AAL is estimated and partitioned using Monte Carlo simulation at the individual home scale, considering insurance coverage and deductible, and the first-floor height (i.e., height of the first floor above the ground), to determine the AAL proportion of homeowners (i.e., apportionment factor) for building and contents, distinguished from that borne by the insurer. In general, AAL estimates suggest that a large portion of the U.S. property flood risk is borne by the flood insurer. The flood insurance policy deductible directly influences the apportionment factor, whereby higher deductibles leave homeowners with a higher annual risk; however, the apportionment factor remains relatively insensitive to coverage values, especially for higher coverage amounts. The homeowner’s flood risk is further reduced by freeboard, with AAL, following an exponential decay trend as freeboard increases. These results reveal new perspectives about how flood insurance protects homeowners from flood risk. In general, the results enhance the proactive decision-making process that allows homeowners to self-assess their degree of preparation and vulnerability to the devastating economic impacts of flood.
Special flood hazard areas (SFHAs), defined as having an annual probability of occurrence of 0.1 or above, are used by U.S. Federal Emergency Management Agency (FEMA) to demarcate areas within which flood insurance purchase is required to secure a mortgage. However, quantifying flood risk within SFHAs can be challenging due to the lack of modeled flood depth data for all return periods. To address this issue, this research quantifies flood risk indicated by average annual loss (AAL) within the A Zone – the subset of the SFHA where wave heights can potentially range from 0 to 3 feet. The methodology resolves the Gumbel quantile function for four distinct flooding cases (i.e., location flooded at return periods exceeding 1.58-, 10-, 25-, and 50-year return period events) and generates synthetic flood hazard parameters for these cases within the 100-year floodplain, as well as with additional elevation above the base blood elevation (BFE), known as freeboard, for single-family homes with different attributes. The results indicate that for single-family homes in the A Zone, with the lowest floor elevated to the BFE, the AAL ranges from 0.3 to 1 percent of the building replacement cost value. Adding one foot of freeboard reduces flood risk by over 90% if the annual flood risk is between the minimum and 25th percentiles, and the 100-year flood depth is less than two feet. The demonstrated approach helps to enhance flood resilience in the A Zone, demonstrating the feasibility of proactive measures to protect communities.
Much of the U.S. petrochemical infrastructure is heavily concentrated along the western coast of the Gulf of Mexico within the impact zone of major tropical cyclone events. Flood impacts of recent tropical disturbances have been exacerbated by an overall lack of recognition of the vulnerabilities to process systems from water intrusion, as well as insufficient disaster mitigation planning. Vulnerability assessment methods currently call for the aggregation of qualitative data to survey the susceptibility of industrial systems to floodwater damage. A means to quantify these consequences is less often employed, resulting in a poor translation of the threat of flood hazards to a crucial element of the economy. This paper reviews flood damage assessment for industrial facilities and presents a component-level conceptual methodology to assess the consequences of flood events. To more effectively communicate loss potential from flood events, the proposed methodology utilizes synthetic estimation to calculate repair requirements, shutdown time, and direct cost.
