Flood — Chester, Pennsylvania

2014-04-30 · near Fairville, Chester, Pennsylvania

Event narrative

Very heavy rain caused widespread poor drainage and moderate to major creek and river flooding throughout Chester County. Two apartment complexes had to be evacuated. Over one hundred roadways were flooded and closed. More than sixty-five people were rescued from trapped vehicles. Three people trapped in their homes by flood waters were rescued. Flooding along the main stem of the Brandywine Creek was the worst since Tropical Storm Floyd on September 16, 1999. Other flooding was the worst since Tropical Storm Irene on August 28, 2011.

In Avondale Borough, flooding along the East Branch of the White Clay Creek forced the evacuation of 300 residents in the Avondale Apartments on First Street late on the afternoon of the 30th. Residents were able to return on the morning of May 1st. In Modena Borough, flooding along the West Branch of the Brandywine Creek forced the evacuation of 400 residents of the Meredith Court Apartments during the early evening on the 30th. They were permitted to return on the morning of May 1st. Shelters were opened for the evacuees. In East Coventry Township, the Pigeon Creek overflowed and forced the closure of Halteman and Kolp Roads. U.S. Route 1 was closed in both directions between Pennsylvania State Route 52 (Lenape Rd.) in East Marlborough Township and U.S. Route 202 (Wilmington Pike) in Chadds Ford Township in Delaware County.

The West Branch of the Brandywine Creek at Honey Brook had moderate flooding and was above its 7 foot flood stage from 329 p.m. EDT on the 30th through 451 a.m. EDT on May 1st. It crested at 9.08 feet at 730 p.m. EDT on the 30th. Farther downstream, the West Branch of the Brandywine Creek at Coatesville had minor flooding and was above its 7 foot flood stage from 329 p.m. EDT on the 30th through 522 a.m. EDT on May 1st. It crested at 8.45 feet at 1200 a.m. EDT on May 1st. Farther downstream, the West Branch of the Brandywine Creek at Modena had moderate flooding and was above its 9 foot flood stage from 349 p.m. EDT on the 30th through 408 a.m. EDT on May 1st. It crested at 10.63 feet at 545 p.m. EDT on the 30th.

The East Branch of the Brandywine Creek at Downingtown had major flooding and was above its 7 foot flood stage from 500 p.m. EDT on the 30th through 307 a.m. EDT on May 2nd. It crested at 13.50 feet at 915 p.m. EDT on the 30th. This was historically the 5th highest crest on record for the creek and the highest crest since August 28, 2011, associated with Tropical Storm Irene.

The main stem of the Brandywine Creek at Chadds Ford had major flooding and was above its 9 foot flood stage from 505 p.m. EDT on the 30th through 1123 p.m. EDT on May 1st. It crested at 16.05 feet at 245 a.m. EDT on May 1st. This was historically the 3rd highest crest on record for the creek and the highest crest since September 16, 1999, associated with Tropical Storm Floyd.

The Red Clay Creek at Kennett Square was above its 7.5 foot flood stage from 535 p.m. EDT through 1108 p.m. EDT on the 30th. It crested at 8.55 feet at 7 p.m. EDT on the 30th, the 7th highest crest on record. The White Clay Creek at Strickersville was above its 9.5 foot flood stage from 505 p.m. EDT on the 30th through 208 a.m. EDT on May 1st. It crested at 12.11 feet at 915 p.m. EDT on the 30th, the 5th highest crest on record and the highest since Tropical Storm Irene on August 28th. The French Creek at Phoenixville was above its 8 foot flood stage from 1258 p.m. EDT on the 30th through 147 p.m. EDT on the 1st. It crested at 9.40 feet at 345 p.m. EDT on the 30th. The Schuylkill River at Pottstown had minor flooding and was above its 12.5 foot flood stage from Midnight EDT through 131 p.m. EDT on May 1st. It crested at 12.90 feet at 830 a.m. EDT on May 1st.

Event precipitation totals included 6.56 inches in Spring City, 6.39 inches in East Nantmeal, 6.16 inches in Unionville, 6.15 inches in Nottingham, 5.91 inches in West Grove and 5.65 inches in Landenberg.

Wider weather episode

A slow moving low pressure system and a deep southerly flow from the Gulf of Mexico and then the Atlantic Ocean dropped heavy rain across Eastern Pennsylvania centered on the 30th. Event precipitation totals averaged from 3 to 6 inches, with the highest amounts in the Philadelphia suburbs. This caused poor drainage and creek and river flooding that reached major levels around the Philadelphia Metropolitan Area. Over 1,000 people had to be evacuated from flooded homes and apartments. The American Red Cross opened several shelters and comfort stations in Delaware and Chester Counties. Numerous water rescues and road closures occurred. the evening commute on the 30th and the morning commute on May 1st were greatly impacted. Regional commuter rail lines in and around Philadelphia had major delays. The Schuylkill River had its highest crest since Tropical Storm Floyd in September of 1999. Other creeks and rivers had their highest crest since Tropical Storm Irene in August of 2011. The steady rain began around noon EDT on the 29th. The rain fell at a fairly steady light to moderate pace until the 30th. Then, the rain fell heavy at times from the morning into the evening of the 30th. Rainfall amounts of around 2 inches fell in the six hour period from 2 p.m. EDT through 8 p.m. EDT on the 30th in the local Philadelphia area. The rain ended from south to north between Midnight EDT and 6 a.m. EDT on May 1st.

The heavy rain was caused by the combination of a strong high pressure system that built over the Canadian Maritimes that initiated the onshore flow and a strong, but slow moving low pressure system. The low pressure system was located in northwest Missouri on the morning of the 29th. It moved northeast to near Chicago during the afternoon of the 29th. The low pressure system then became nearly stationary in southern Wisconsin as its cold front reached Ohio early on the 30th. Then a new low pressure system developed on the frontal boundary and was over Eastern Tennessee on the morning of the 30th. The low pressure system reached West Virginia during the late afternoon on the 30th as its warm front started to move through Delmarva. The low pressure system reached north central Maryland at 11 p.m. EDT on the 30th as its warm front reached extreme southeast Pennsylvania and central New Jersey. The low pressure system reached the Allentown, Pennsylvania area at 5 a.m. EDT on May 1st and then was absorbed again into the frontal boundary associated with the original low as it moved into New York State that morning. The steady rain ended as the low pressure system passed north of Pennsylvania.

View location on OpenStreetMap → (39.8394, -75.6087)

Source: NOAA Storm Events Database, event_id 512909. Narrative written by the NWS forecast office that issued the report.