Flash Flood — Montgomery, Pennsylvania

2001-06-16 to 2001-06-17 · near South Portion, Montgomery, Pennsylvania

Wider weather episode

The remnants of tropical storm Allison drenched the southern halves of Montgomery and Bucks Counties and Philadelphia with up to 10 inches of rain. Torrential downpours occurred from early afternoon through the late evening on the 16th. Severe flooding occurred along the Sandy Run, Wissahickon, Pennypack and Neshaminy Basins. The flooding caused and then hampered fire fighters battling an apartment fire in Upper Moreland Township. Six persons perished in the fire. A 63-year-old man died when his 1997 Toyota was swept into the Wissahickon Creek in Whitemarsh Township (Montgomery County). Several bridges were damaged or washed out including a couple on the SEPTA Regional Rail Lines. About 241 homes were destroyed and 1,386 others were damaged. The torrential rains liquified the ground and caused weak trees to fall over. About 70,000 PECO Energy customers lost power. Both Bucks and Montgomery Counties were declared disaster areas. Preliminary damage estimates were 35 million dollars. Damage to roads and bridges alone was around 5 million dollars. Montgomery County was hit the hardest with Abington Township, Cheltenham Township, Hatboro Borough, Horsham Township, Lower Moreland Township, Upper Dublin Township and Upper Moreland Township affected the most. In Upper Moreland Township, six people died in an apartment building fire that apparently was triggered by rising flood waters from the nearby Pennypack Creek. Flood waters rose 10 to 20 feet at the Village Green Apartment Complex and inundated the area. Firefighters were rescuing people, some from the second floor, when the complex was struck by a natural gas explosion. The fire apparently started after rising flood waters knocked over hot water heaters in building A of the complex and caused the gas leak. Rising flood waters prevented firefighters from battling the flames. Two buildings in the complex were destroyed by the fire. Two others had smoke and water damage while the remaining 16 buildings were evacuated. About 200 persons were sheltered. Elsewhere in the township, rescuers bcame trapped in the Pennypack Creek trying to save others. Flood damage caused the condemnation of the Bonnet Lane Shopping Center. In Hatboro, four people were trapped by rising flood waters at the Old Mill Inn and about 150 vehicles at a Dodge Dealership were damaged beyond repair. In Whitemarsh Township, a 63 year-old man drowned when his Toyota was found in the Wissahickon Creek. Elsewhere in the township, flooding along the Sandy Run Creek destroyed the SEPTA Fort Washington (R5 Doylestown Line) Bridge. Flood waters also toppled poles that supported the power lines. Repairs were expected to take three weeks. Shuttle buses were used to transport the 12,000 affected commuters. In Abington Township, SEPTA tracks were washed out and cut off the use of the R2 (Warminster) and R3 (Trenton) lines. In Whitpain Township, a storm drain near the swollen Wissahickon Creek was overwhelmed. The flood waters caused the collapse of a warehouse and a 3 to 4 foot surge of water down Maple Street. About 25 families were rescued, some from their second floor or roof. About a dozen homes were damaged by flood waters that reached into the first floor. The Pennsylvania Turnpike was closed between the Willow Grove and Norristown Exits. Except for the Fort Washington Interchange, the turnpike was reopened on the 17th. In Bucks County, Bensalem Township, New Britain Township, Middletown Township, Warminster Township and Warrington Township were hardest hit. Scores of motorists were trapped in vehicles; house trailers were seen floating. A State of Emergency was declared in Warrington Township as flooding caused a chlorine leak. Elsewhere in the township, people were trapped within a collapsed home. In Philadelphia, flooding along the Wissahickon Creek caused a couple of road closures. Several roads were also closed in the northern part of the city.In Bucks County, the Neshaminy Creek at Langhorne was above its 9 foot flood stage from 1059 p.m. EDT on the 16th through 421 p.m. EDT on the 17th. It crested at 16.87 feet at 830 a.m. EDT on the 17th. The Little Neshaminy Creek at Neshaminy reached its 8 foot flood stage from 716 p.m. EDT on the 16th through 409 a.m. EDT on the 17th. It crested at 14.05 feet at 1030 p.m. EDT on the 16th. In Montgomery County, the East Branch of the Perkiomen Creek at Schwenksville briefly touched its 7 foot flood stage at 5 p.m. EDT on the 16th. In Philadelphia, the Wissahickon Creek at Philadelphia was above its 5 foot flood stage from 8 p.m. EDT on the 16th through 140 p.m. EDT on the 17th. It crested at 9.73 feet at 430 a.m. EDT on the 17th. The Pennypack Creek at Pennypack was above its 7 foot flood stage from 715 p.m. EDT on the 16th through 836 a.m. EDT on the 18th. It crested at 13.12 feet at 1045 p.m. EDT on the 16th. The Frankford Creek at Frankford was above its 7 foot flood stage from 836 p.m. EDT on the 16th through 141 a.m. EDT on the 17th. It crested at 8.82 feet at 1101 p.m. EDT on the 16th. Storm totals included 10.17 inches in Chalfont (Bucks County), 10.16 inches at the Willow Grove NAS in Montgomery County, 9.35 inches in Doylestown (Bucks County) and Wyncote (Montgomery County), 9.00 inches in Abington (Montgomery County), 8.00 inches in Horsham (Montgomery County), 7.40 inches in Warrington (Bucks County), 5.73 inches in Ambler (Montgomery County), 4.81 inches in Furlong (Bucks County), 4.54 inches in Southampton (Bucks County), 3.83 inches in Wynnewood (Montgomery County), 3.43 inches in Somerton (Philadelphia) 3.38 inches at the Philadelphia International Airport and 2.62 inches at the Franklin Institute within Philadelphia. The low pressure system that was the remnants of Tropical Storm Allison, was very persistent and slow moving. It moved from northeast North Carolina the afternoon of the 15th to near Norfolk the morning of the 16th to the Virginia Capes during the afternoon of the 16th and just east of Atlantic City during the morning of the 17th. Similar to Hurricane Floyd, a cold front was approaching the region from central Pennsylvania on the 16th. An extremely moist and unstable southeast flow preceded both these features. The slight rise in elevation from the coastal plain to the Piedmont in Southeast Pennsylvania (called the fall line) was enough to enhance the precipitation and drop copious amounts across this area.

Source: NOAA Storm Events Database, event_id 5253964. Narrative written by the NWS forecast office that issued the report.