Abstract
Abstract. A growing body of work suggests that the extreme weather events that drive inland flooding are likely to increase in frequency and magnitude in a warming climate, thus potentially increasing flood damages in the future. We use hydrologic projections based on the Coupled Model Intercomparison Project Phase 5 (CMIP5) to estimate changes in the frequency of modeled 1 % annual exceedance probability (1 % AEP, or 100-year) flood events at 57 116 stream reaches across the contiguous United States (CONUS). We link these flood projections to a database of assets within mapped flood hazard zones to model changes in inland flooding damages throughout the CONUS over the remainder of the 21st century. Our model generates early 21st century flood damages that reasonably approximate the range of historical observations and trajectories of future damages that vary substantially depending on the greenhouse gas (GHG) emissions pathway. The difference in modeled flood damages between higher and lower emissions pathways approaches USD 4 billion per year by 2100 (in undiscounted 2014 dollars), suggesting that aggressive GHG emissions reductions could generate significant monetary benefits over the long term in terms of reduced flood damages. Although the downscaled hydrologic data we used have been applied to flood impacts studies elsewhere, this research expands on earlier work to quantify changes in flood risk by linking future flood exposure to assets and damages on a national scale. Our approach relies on a series of simplifications that could ultimately affect damage estimates (e.g., use of statistical downscaling, reliance on a nationwide hydrologic model, and linking damage estimates only to 1 % AEP floods). Although future work is needed to test the sensitivity of our results to these methodological choices, our results indicate that monetary damages from inland flooding could be significantly reduced through substantial GHG mitigation.
Highlights
Inland floods are among the most costly natural disasters in the United States (e.g., Pielke Jr. and Downton, 2000), with annual damages ranging from hundreds of millions to many tens of billions of dollars over the past century (Downton et al, 2005; NOAA, 2016)
This study evaluates 21st century flood risk and floodrelated damages across the contiguous United States (CONUS) using downscaled hydrologic projections from 29 global climate models (GCMs) and two representative concentration pathways (RCPs) for greenhouse gas (GHG) forcing
Since the hydrographs generated by the downscaled hydrology outputs are unique to each GCM–RCP combination, each model produces its own time series of flooding at each stream segment
Summary
Inland floods are among the most costly natural disasters in the United States (e.g., Pielke Jr. and Downton, 2000), with annual damages ranging from hundreds of millions to many tens of billions of dollars over the past century (Downton et al, 2005; NOAA, 2016). In 2016, inland flooding events in Louisiana and North Carolina alone caused over USD 10 billion of physical damages to homes, businesses, and other assets (Fortune, 2016; LED, 2016). This follows on other recent years with extreme flooding in Michigan (2014) and Colorado (2013) and the mid-Atlantic floods caused by Superstorm Sandy (Hurricane Sandy) in 2012 (NOAA, 2016). The science linking changes in climate extremes to human-caused warming is advancing (e.g., Trenberth et al, 2015; National Academies of Sciences, Engineering, and Medicine, 2016), there are still many challenges to attributing observed historical trends in flooding. As a complement to these attribution studies, forward-modeling approaches using linked climate-hydrologic models could help to characterize future changes in flood risk and vulnerability (e.g., Das et al, 2013; Hirabayashi et al, 2013; Arnell and Gosling, 2016)
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