A Methodology to Assess Land Use Development, Flooding, and Wetland Change as Indicators of Coastal Vulnerability

Abstract

Coastal areas around the world are becoming increasingly urban, which has increased stress to both natural and anthropogenic systems. In the United States, 52% of the population lives along the coast, and North Carolina is in the top 10 fastest growing states. Within North Carolina, the southeastern coast is the fastest growing region in the state. Therefore, this research has developed a methodology that investigates the complex relationship between urbanization, land cover change, and potential flood risk and tested the approach in a rapidly urbanizing region. A variety of data, including satellite (PlanetScope) and airborne imagery (NAIP and Lidar) and vector data (C-CAP, FEMA floodplains, and building permits), were used to assess changes through space and time. The techniques consisted of (1) matrix change analysis, (2) a new approach to analyzing shorelines by computing adjacency statistics for changes in wetland and urban development, and (3) calculating risk using a fishnet, or tessellation, where hexagons of equal size (15 ha) were ranked into high, medium, and low risk and comparing these results with the amount of urbanization. As other research has shown, there was a significant relationship between residential development and wetland loss. Where urban development has yet to occur, most of the remaining area is at risk to flooding. Importantly, the combined methods used in this study have identified at-risk areas and places where wetlands have migrated/transgressed in relationship to urban development. The combination of techniques developed here has resulted in data that local government planners are using to evaluate current development regulations and incorporating into the new long-range plan for the County that will include smart growth and identification of risk. Additionally, results from this study area are being utilized in an application to the Federal Emergency Management Agency’s Community Response System which will provide residents with lower flood insurance costs.