Shifting landscapes of risk: Quantifying pluvial flood vulnerability beyond the regulated floodplain

Theoretical Boundaries of Annual Flood Risk for Single-Family Homes Within the 100-Year Floodplain

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.

A simulation-based approach for assessing regional and industrial flood vulnerability using mixed-MRIO model: A case study of Hubei Province, China

Given the unstoppable forces behind regional economic integration trends, damages from a flood disaster in a specific area will influence correlative cities through industrial linkages and make economic systems more vulnerable. Assessing urban vulnerability is an essential part of flood prevention and mitigation, and also a hot topic of recent research. Therefore, this study (1) constructed a mixed multiregional input-output (mixed-MRIO) model to explore ripple effects on other regions and sectors when production in a flooded area is constrained, and (2) applied this model to characterize the economic vulnerability of cities and sectors in Hubei Province, China by simulation. First, various hypothetical flood disaster scenarios are simulated to reveal the ripple effects of different events. The composite vulnerability is assessed by analyzing economic-loss sensitivity rankings across scenarios. Then, the model is applied to the case of a 50-year return period flood that occurred in Enshi City, Hubei Province, on July 17, 2020 to empirically verify the usefulness of such a simulation-based approach in evaluating vulnerability. The results indicate vulnerability is higher in Wuhan City, Yichang City, and Xiangyang City and for three manufacturing sector types: livelihood-related manufacturing, raw materials manufacturing, and processing and assembly manufacturing. Such cities and industrial sectors with high vulnerability will significantly benefit from prioritization in flood management.