You are here:
Projected changes to IDF curves from dynamically downscaled scenarios
Citation:
Jalowska, A., T. Spero, D. Line, B. Doll, AND J. Bowden. Projected changes to IDF curves from dynamically downscaled scenarios. ASABE 2021 Annual International Meeting July, NA, NC, July 11 - 14, 2021.
Impact/Purpose:
Historical climate records show an increasing trend in the frequency and intensity of extreme rainfall events across the eastern U.S., which has been documented in the Third and Fourth National Climate Assessments. Climate models project a trajectory that increases the intensity and frequency of the extreme events throughout the 21st century. However, projecting magnitude of future precipitation changes—especially the extremes—is difficult. In this study, we introduce the novel Design Rainfall Approach (DRA) and apply it to the Neuse River Watershed, NC using Hurricane Matthew from 2016 to quantify future changes in runoff.
Description:
Historical climate records show an increasing trend in the frequency and intensity of extreme rainfall events across the eastern U.S., which has been documented in the Third and Fourth National Climate Assessments. Eastern North Carolina (ENC) is among the most vulnerable regions in the U.S. to devastating rainfall and widespread flooding, and it has been affected by over 380 tropical cyclones (TC) since 1851. The most devastating flooding events in ENC were associated with TCs that occurred within last 25 years. Climate models project a trajectory that increases the intensity and frequency of the extreme events throughout the 21st century. However, projecting magnitude of future precipitation changes—especially the extremes—is difficult. In this study, we introduce the novel Design Rainfall Approach (DRA) and apply it to the Neuse River Watershed, NC using Hurricane Matthew from 2016. DRA projects potential changes to individual events by using downscaled projections for two 30-year periods. DRA eliminates individual model biases and corrections by comparing the relative changes in the projections between those future periods and applying them to an observed extreme event. Potential changes to extreme rainfall at the end of the 21st century were derived from two global climate models- the Community Earth System Model (CESM) and the Geophysical Fluid Dynamics Laboratory Coupled Climate Model (CM3). The projections from the global models were dynamically downscaled using the Weather Research and Forecasting (WRF) model under two greenhouse gas emission scenarios (RCP4.5 and 8.5). Relative changes in future Intensity-Duration-Frequency (IDF) curves derived from dynamically downscaled projections were applied to observed precipitation associated with Hurricane Matthew to project rainfall from that event at “2100”. Matthew “2100” rainfall was then used in a hydrologic model (HEC-HMS) to simulate “2100” discharges for the Neuse River. The results suggest that peak discharges for Matthew “2100” in Goldsboro, NC could increase by ~450 cms under RCP 4.5 and by ~2,500 cms under RCP 8.5. Peak discharges for the 50-, 100-, and 500-yr storms were projected to substantially increase by 58-152% under RCP 8.5, with the greatest increase projected for the most extreme (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 and unprecedented (in modern history) flooding.