Risky Business: How Humans Will Shape Floodplain Landscapes Over the 21st Century

Globally, fluvial and pluvial flooding is the costliest natural hazard, accounting for over 40% of $7 trillion (2015 USD) in natural disaster losses from 1900 to 2015. The Southeastern USA is particularly vulnerable to flood hazards, as it is characterized by relatively flat, low-lying watersheds with wide, shallow floodplains and is also experiencing dynamic climate and land use/land cover change. While these flood risk drivers separately have received attention for increasing runoff volume and routing efficiency, the combined effects of incremental land use/land cover changes and regional climate change on flood hazards and associated risk in coastal plain watersheds are still poorly understood. As a result, floodplain extent and related damages may evolve in novel patterns incongruent with current practices targeting loss mitigation and future development. Here, we investigate the influence of decadal changes in land use/land cover and climate on the hydrology of the Neuse River watershed in eastern North Carolina using a loosely coupled physics-based, distributed hydrologic and hydraulic modeling framework. We simulate changes in flood hazard at a decadal timesteps through 2050 to determine the hydrologic response of each sub-basin relative to its 1) spatial extent, 2) stream order and 3) degree of land use/land cover change. We then map future flood hazard scenarios for the urban center of Goldsboro, North Carolina and use them to identify structures in and adjacent to the 100-year floodplain that experience increased flood risk. Not only will the outcomes of this research be crucial for flood risk communication, but this study will also improve the scientific understanding of regional hydrological responses to continental-scale projections of climate and land use/land cover change.