Hydrology, Hydraulics and Hydrometeorology of Floods in the Eastern United States
Baltimore Jim Smith Ecosystem Princeton University Study LTER Outline and Themes
How does the 100 year flood vary over the eastern US?
Complex Terrain
Central Appalachians Land – Ocean Urban Environment
Basin Scale: “3 Floods”
Warm Season Thunderstorm Systems – Smethport PA July 1942 Tropical Cyclones – Hurricane Agnes, June 1972 Winter/Spring Extratropical Systems – March 1936
Extreme Floods and Tropical Cyclones
Hurricane Isabel 18 September 2003
Annual Flood Peak Discharge South Fork Shenandoah River Drainage Area: 1640 mi2 Record Length: 78 Years
10 Year Flood: 47,500 cfs 100 Year Flood: 130,000 cfs Tropical Cyclones and Annual Flood Peaks
572 USGS Streamflow Stations.
More than 75 year record length.
NOAA Atlantic Hurricane Data Base (HURDAT). Isabel Rainfall (mm) – Weather Isabel Rainfall (mm) – HydroNEXRAD Research and Forecasting (WRF) Rainfall Observations Model. “Envelope Curve”: Flood Peaks in the Eastern US Thunderstorm Frequency – Catastrophic Floods – Complex Terrain
Rapidan Storm – 27 June 1995 Rapidan Storm WRF Simulation
“19 July” Storms
Smethport PA 19 July 1942 30.8 inches – 4 Hours
19 July 1996
1889 Rockport WVA 1942 Smethport PA 1977 Johnstown PA 1996 Redbank Creek, PA Moores Run, June 13, 2003 Flood Frequency – Charlotte NC Storm total rainfall (mm)
Storm Total Lightning (CG Storm -2 Total strikes km ) Rain (mm)
7 July 2004 - Flood of Record in Dead Run Storm total rainfall (mm) 7 July 2004 Yellow – July 7 Inundation Area Light blue – FEMA 500-yr Floodplain Dark blue – FEMA 100-yr Floodplain
Life Cycle of Warm Season Thunderstorm Systems:
1) Initiation over Blue Ridge. 2) Propagation over Piedmont. 3) Interaction with urban environment and land – water circulation systems.
CG lightning strikes on 13 June 2003; color coding indicates time (hour) of occurrence. Summary and Conclusions
* Tropical cyclones control extreme flooding in much of the eastern US; there is pronounced spatial heterogeneity in tropical cyclone flooding. * Mountainous terrain (orographic precipitation mechanisms) plays a central role in the extreme flood hydrology of the eastern US. * Thunderstorm systems in mountainous terrain of the eastern US have produced some of the largest rainfall accumulations in the world for time intervals less than 6 hours. * Envelope curve of flood peak magnitudes for the eastern US includes numerous urban floods with relatively short return intervals. * “Climatology” of urban floods is directly linked to the climatology of warm season thunderstorm systems.
Weather Research and Forecasting Model - 7 July 2004 Simulations
Conclusions from WRF Model Simulations
HydroNEXRAD Convergence-induced Storm Total Rain “spin-up” along Blue Ridge Chesapeake Bay “thermal boundary” plays important role in evolution of storm system “Urban Canopy” has important impacts on storm evolution No “UHI” effect Aerosol effects – suppression, enhancement or redistribution. WRF Storm Total Rainfall (mm) PA
NJ
DE
VA
Baisman Run at Broadmoor !.
!. Gwynns Falls near Delight
Gwynns Falls at Villa Nova !. !. Moores Run at Dead Run at Franklintown !. Radecke Ave
Gwynns Falls at Washington Blvd !. Baltimore City
0 2.5 5 10 15 20 Kilometers CG Lightning Strikes on July 7, 2004
Initiation along Blue Ridge, propagation over Piedmont, interaction with urban environment and land - water boundaries (Chesapeake Bay)
Storm Total LightningStorm Total(CG -2 strikesLightning km ) Storm Strikes km-2 Total Rain (mm)
•Return interval of rainfall accumulations over Dead Run: < 10 years at 15 minutes; > 300 years at 120 minutes.
Storm Evolution: 1845 - 2115 UTC on 7 July 2004 Evolution of Storm Elements on 7 July 2004