Comprehensive Flood Impact Assessment for Iowa Bridge Infrastructure Using Integrated AHP and Fuzzy AHP Analysis

Flooding poses a significant threat to transportation infrastructure like bridges and culverts in regions like Iowa, where infrastructure deficiencies, unpredictable climate patterns, and geographic factors all contribute to vulnerability. This study evaluates the susceptibility of over 24,000 bridges in Iowa to flood-induced damage by considering both the likelihood of flooding and its potential negative impacts on bridge functionality, using the Analytic Hierarchy Process (AHP) and Fuzzy AHP methods. By combining bridge inventory datasets with historical flood data, this study assesses flood risks across multiple flood scenarios (50, 100, and 500 years return period). Factors such as bridge age, condition, traffic volume, detour lengths, and flood likelihood were used to calculate the impact indices for each bridge. Two distinct impact index sets were computed and visualized across the state at individual locations, county scales, and through a Kernel-based heatmap analysis where the population data was incorporated as an additional layer to provide a broader perspective on the potential societal impacts. The results indicate areas where a large portion of the bridge network is at risk of flooding, potentially leading to major disruptions and impacts on society. This research provides insights into the weaknesses in Iowa’s bridge network and contributes to understanding how transportation infrastructure is impacted by flooding.