Name: Flash Flood in Delaware, August 11 to 12, 2001
Start: 2001-08-11T15:00
End: 2001-08-12T05:00
Location: Delaware

Where it happened

Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
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The toll

Deaths: 0
Injuries: 0
Property damage: $1.1 million
Crop damage: None recorded
Events: 1

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS PHI wrote it up.

Slow moving thunderstorms with torrential rains inundated southwestern Sussex County during the late afternoon of the 11th. Doppler Radar storm total estimates reached 8.4 inches around Seaford. Aside from the far northeast and southeast part of the county, storm total estimates exceeded 3 inches in the rest of the county. The torrents led to flooding of streams and an eventual dam failure around midnight EDT on the 12th. About a dozen municipal streets were closed because of the flooding including Delaware State Route 20. About Midnight EDT, the 100 year-old dam on Hearns Pond gave way. The 60 acre pond drained out and a bulkhead along U.S. Route 13A was undercut by the flood waters which then undermined the roadway. The flooding caused extensive damage to the historic Hearns and Rawlings Mills. Fifteen patients of a nearby nursing home were evacuated to the second floor. U.S. Route 13A was closed and was expected to take until Friday the 17th to be repaired and reopened. The Bridgeville Branch flooded and covered the North Cannon Street Bridge in Bridgeville. Storm totals included both 5.30 inches in Georgetown and Greenwood and 4.95 inches in Delmar. Damage was estimated at $1.1 million dollars. Farmers also feared the heavy rain may have damaged vine crops (melons and cucumbers). No serious injuries were reported.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Aug 11, 1:30 PM EST, 1 hour 30 minutes earlier.

Area forecast discussion, Aug 11, 1:30 PM EST, 1 hour 30 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
230 PM EDT SAT AUG 11 2001

WE WILL BE ISSUING A FFA FOR MOST OF OUR CWA WITH THIS NEXT FCST PKG
FOR TNGT. GRANTED THE 2ND PERIOD MIGHT ALSO NEED A FFA BASED ON THE
LINGERING LOCN OF THE FNT...BUT DON/T WANT TO BOX MIDN SHIFT IN AND
THEY CAN REACCESS AFT TNGT/S ACTVTY.

UPSHOT OF ALL OF THIS IS BNDRY IS RMNG QUASI-STATINARY ACRS OUR CWA.
LCL FFA CHECKLIST IS 5 OF 6 AS PWATS ARE GREATER THAN 2
IN/THICKNESSES ARE GREATER THAN NML/AVN K INDEX FCST REACHES
40/INSTAB EXISTS THRU TNGT AND WE HAVE A WK SHRT WV TO ENHANCE PCPN
PTNL AS FNTL BNDRY DRIFTS BACK TO THE N. AVN FCSTG ENUF INSTAB
OVRNGT TO GIVE US THE PTNL TO HAVE CONVECTION GO THRU THE NGT WITH
THE APCHG SHRTWV. HIEST FCSTD K INDEX AND PACHG SHRTWV ACTUALLY MOVE
IN TWD MRNG. INCRG (ALBEIT NOT THAT STG) S-SWLY FLOW AT H8 ALSO APRS
TO CONVERGE OVR OUR CWA.  ONE MISSING INGRED IS A DECENT LLVL HODO
(WHICH ACTUALLY IPVS TWD SUN EVE)...BUT SLO MOVEMENT OF THE TSRAS
HAVE NEGATED THIS ONE LACKING FEAT SO FAR TDY.

THERE IS A CHC THAT THE ONGOING CONVECTION IN VA MIGHT SHUT HVY PCPN
FTHR TO THE N...ONE REASON FOR NOT INCLDG OUR NRNMST CTYS AND ALSO
REASON ITS A WATCH.  WOULD HAVE LIKED TO NOT INCLD BERKS AND THE
LEHIGH VLY ALSO...BUT THEY HAVE HAD HEAVY RAIN AND FLOODING ALRDY
AND FFG IN THE SRN PARTS OF BERKS/LEHIGH CTY WOULD BE PRETTY LO.

WILL GO LIKELY/CAT POPS WITH HVY PCPN WORDING FOR TNGT/SUN. IN
GENERAL GUID MINS LOOK OK FOR TNGT...MAX TEMPS A BIT TOASTY ON SUN.

DIF BTWN ETA (IMPLIED NGM MOS) AND AVN FOR HOW QUICKLY WE GET INTO
THE DRIER AIR ON MON. ATTM WE PLAN ON LEAVING POPS IN THE CHC CAT AS
H5 TROF IS STILL TO OUR W. WILL FOLLOW SAME TREND FOR TEMP FCST VS
GUID FOR SUN NGT AND MON.

ONE YEAR ANNIVERSARY OF HORRIFIC FLOODING IN SUSSEX COUNTY NJ.
THANKFULLY UA PAT IS NOT THE SAME AS THAT DAY TODAY.

MAR: ALL/S QUIET.

.PHI...FFA ALL ZONES INTO TNGT EXCEPT FOR PA54/55 AND NJ1/7/8.

TFG

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Sussex

When: August 11, 3:00 PM EST to August 12, 5:00 AM EST
Where: Sussex County, Southwest Portion
Property damage: $1.1 million
Reported by: EMERGENCY MANAGER
Coordinates: 38.683, -75.339 (the zone’s center; the record gives no point)

What these are

Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Delaware in 2001 Every state in 2001 This day in weather history Warnings in Delaware, August 2001

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5268675.