Future pluvial flooding associated with projected extreme rainfall in North Carolina, USA
In recent years Eastern North Carolina experienced several devasting floods associated with rainfall from tropical storms. Analysis of climate records show an increasing trend in the frequency and intensity of extreme rainfall events across the eastern U.S. Recent climate research suggests that the frequency and magnitude of extreme precipitation in the eastern United States will further increase throughout the twenty-first century. Quantification of future changes in extreme events is challenging, yet fundamental for storm-water managers.
In this study two global climate models- the Community Earth System Model (CESM) and the Geophysical Fluid Dynamics Laboratory coupled climate model (CM3)- were dynamically downscaled using the Weather Research and Forecasting (WRF) model, under two greenhouse gas emission scenarios (RCP4.5 and 8.5). Here we present a novel approach to use data from dynamically downscaled projections as basis to compute future changes in Intensity-Duration-Frequency (IDF) curves for the Neuse River Basin in North Carolina. The projected changes in local precipitation (~50%) surpass values published to date for U.S. regions, however they are analogous with extreme precipitation events in the U.S. in the early 21st century.
The projected changes in precipitation by the end of 21st century, were applied to observed precipitation associated with Hurricane Matthew (2017). Developed Hurricane Matthew rainfall quantities at “2100” were then used in HEC-HMS model to simulate “2100” discharges for the Neuse River. The results suggest that peak discharges for Mathew “2100” in Goldsboro, NC could increase by ~450 cms under RCP 4.5 scenario and by ~2,500 cms under RCP 8.5 scenario. Peak discharges for the 50-, 100-, and 500-yr storms were projected to increase from 58-152% for RCP 8.5 with the greatest increase for the 500-yr and larger events. The results indicate that by the end of century, the peak discharge for the 100-yr storm may be equivalent to the peak of the current 500-yr storm producing disastrous flooding.