Hydrology, Hydraulics and Hydrometeorology of Floods in the Eastern United States

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Hydrology, Hydraulics and Hydrometeorology of
Floods in the Eastern United States
Baltimore Ecosystem Study LTER
Jim Smith Princeton University
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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
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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
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Tropical Cyclones and Annual Flood Peaks
572 USGS Streamflow Stations. More than 75 year
record length. NOAA Atlantic Hurricane Data Base
(HURDAT).
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Isabel Rainfall (mm) Weather Research and
Forecasting (WRF) Model.
Isabel Rainfall (mm) HydroNEXRAD Rainfall
Observations
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Envelope Curve Flood Peaks in the Eastern US
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Thunderstorm Frequency Catastrophic Floods
Complex Terrain
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Rapidan Storm 27 June 1995
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Rapidan Storm WRF Simulation
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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
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Moores Run, June 13, 2003
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Flood Frequency Charlotte NC
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Storm total rainfall (mm)
Storm Total Lightning (CG strikes km-2)
Storm Total Rain (mm)
7 July 2004 - Flood of Record in Dead Run
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7 July 2004
Storm total rainfall (mm)
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Yellow July 7 Inundation Area Light blue FEMA
500-yr Floodplain Dark blue FEMA 100-yr
Floodplain
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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.
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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.

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Weather Research and Forecasting Model - 7 July
2004 Simulations
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Conclusions from WRF Model Simulations Convergenc
e-induced 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.
HydroNEXRAD Storm Total Rain
WRF Storm Total Rainfall (mm)
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CG Lightning Strikes on July 7, 2004
Initiation along Blue Ridge, propagation over
Piedmont, interaction with urban environment and
land - water boundaries (Chesapeake Bay)
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Storm Total Lightning (CG strikes km-2)
Storm Total Lightning Strikes km-2
Storm Total Rain (mm)

• Return interval of rainfall accumulations over
  Dead Run
• lt 10 years at 15 minutes
• gt 300 years at 120 minutes.

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Storm Evolution 1845 - 2115 UTC on 7 July 2004
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Evolution of Storm Elements on 7 July 2004
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