Precipitation Extremes and Flood Frequency in a Changing Climate in Southeastern Virginia

Despite the advances in climate change modeling, extreme events pose a challenge to develop approaches that are relevant for urban stormwater infrastructure designs and best management practices. The study first investigates the statistical methods applied to the land-based daily precipitation series acquired from the Global Historical Climatology Network-Daily (GHCN-D). Additional analysis was carried out on the simulated Multivariate Adaptive Constructed Analogs (MACA)-based downscaled daily extreme precipitation of 15 General Circulation Models and Weather Research and Forecasting-based hourly extreme precipitation of North American Regional Reanalysis to discern the return period of 24-hr and 48-hr events. We infer that the GHCN-D and MACA-based precipitation reveals increasing trends in annual and seasonal extreme daily precipitation. Both BCC-CSM1-1-m and GFDL-ESM2M models revealed that the magnitude and frequency of extreme precipitation events are projected to increase between 2016 and 2099. We conclude that the future scenarios show an increase in magnitudes of extreme precipitation up to three times across southeastern Virginia resulting in increased discharge rates at selected gauge locations. The depth-duration-frequency curve predicted an increase of 2-3 times in 24- and 48-h precipitation intensity, higher peaks, and indicated an increase of up to 50% in flood magnitude in future scenarios.