A Methodical Assessment of Floodplains in Mixed Land Covers Encompassing Bridges in Alabama State: Implications of Spatial Land Cover Characteristics on Flood Vulnerability

Abstract

The mixed land covers encompassing bridges (MLB) are integral indicator of the socio-economic hydrological system, and their progressions are vital for flood risk assessment. However, most of the previous studies have neglected a thorough evaluation of MLBs (e.g., types, areas, and depths) on impacting flood vulnerability. This paper addresses this research gap by methodically assessing the spatial characteristics of MLBs in floodplains and their divergent impacts on flood vulnerability using four case studies of Alabama State in the USA. The hydrological and bridge data were synthesized from United States Geological Survey and National Bridge Inventory, respectively. A union of Hydrologic Engineering Center's-River Analysis System (HEC-RAS), Geographic Information System, and Surface Difference Model were employed to retrieve water surface profiles and floodplain assessments in MLBs. The results highlighted that the occurrence of floodplains was more correlated to flood depths compared to flood areas in the MLBs of Alabama. The spatial contribution of the diverse MLBs in producing deep (19%) and shallow (30%) flood depths in the bridges of Alabama were 49%, while medium flood depths were impacted only on 4% of the MLBs. The highest and lowest flood areas were noticed in the MLBs of pastures and mixed forests, respectively. Overall, the findings implied that the contribution of the individual MLBs in floodplains is multifaceted in the bridges of Alabama with spatially varying land cover distribution. Further, it is recommended that for assessing flood vulnerability, the stakeholders should focus not only on the MLBs but also on its spatially dynamic characteristics.