Abstract

Deltas, estuaries, and wetlands are prone to frequent coastal flooding throughout the world. In addition, a large number of people in the United States have settled in these low-lying regions. Therefore, the ecological merit of wetlands for maintaining sustainable ecosystems highlights the importance of flood risk and hazard management in these regions. Typically, hydrodynamic models are used for coastal flood hazard mapping. The huge computational resources required for hydrodynamic modeling and the long-running time of these models (order of hours or days) are two major drawbacks that limit the application of these models for prompt decision-making by emergency responders. In the last decade, DEM-based classifiers based on Height Above Nearest Drainage (HAND) have been widely used for rapid flood hazard assessment demonstrating satisfactory performance for inland floods. The main limitation is the high sensitivity of HAND to the topography which degrades the accuracy of these methods in flat coastal regions. In addition, these methods are mostly used for a given return period and generate static hazard maps for past flood events. To cope with these two limitations, here we modify HAND and propose a composite hydrogeomorphic index for rapid flood hazard assessment in coastal areas. We also propose the development of hydrogeomorphic threshold operative curves for real-time flood hazard mapping. We select the Savannah river delta as a testbed, calibrate the proposed hydrogeomorphic index on Hurricane Matthew and validate the performance of the developed operative curves for Hurricane Irma. Validation results demonstrate that the operative curves can rapidly generate flood hazard maps with satisfactory accuracy. This indicates the high efficiency of our proposed methodology for fast and accurate estimation of hazard areas for an upcoming coastal flood event which can be beneficial for emergency responders and flood risk managers.

Highlights

  • Populated coastal areas are some of the most productive ecosystems on Earth

  • This indicates the high efficiency of our proposed methodology for fast and accurate estimation of hazard areas for an upcoming coastal flood event which can be beneficial for emergency responders and flood risk managers

  • To validate the effectiveness and reliability of the developed operative curves, we use them to identify hazard areas corresponding to Hurricane Irma, and we compare their accuracy with the reference map provided by the hydrodynamic model for this flood event

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Summary

Introduction

Populated coastal areas are some of the most productive ecosystems on Earth. Coastal wetlands provide important services to society, including flood attenuation, water storage, carbon sequestration, nutrient cycling, pollutant removal, and wildlife habitat (Barbier, 2019; Land et al., 2019; Wamsley et al, 2010). Characterizing the hydrological processes unique to coastal areas is tremendously important for ensuring the sustainability of these ecosystem services. Endangered coastal ecosystems are threatened by anthropogenic effects including direct impacts of human activities (i.e. urbanization and navigational development) or indirect impacts (e.g. sea level rise (SLR), and hydroclimate extremes exacerbated by climate change (Alizad et al, 2018; Kirwan and Megonigal, 2013; Wu et al, 2017). Urbanization hinders wetland migration toward upland areas in an effort to cope with rising water levels (WLs) (Schieder et al, 2018).

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