Flood — Northampton, Pennsylvania

2011-03-10 to 2011-03-12 · near Walnutport, Northampton, Pennsylvania

Event narrative

Northampton County was affected by the one two combination of flooding along the Lehigh and Delaware Rivers. Flooding along these rivers also caused smaller streams and rivers to back up and flood. The flooding also caused considerable damage along the towpaths of both the Lehigh and Delaware River Canals. In Bethlehem, flooding along the Lehigh River forced the evacuation of about 100 residents along Wilson Avenue. While homes were not affected, sections of Wilson Avenue as well as Sculac and Farmersville Roads were impassable. Evacuations also occurred along the Monocacy Creek in Bethlehem's Colonial Industrial Quarter. In Easton, dozens of people were evacuated along Bushkill Drive after the Bushkill Creek flooded. Homes suffered basement flooding. Larry Holmes and Lehigh Drives were closed along the Lehigh River. Pennsylvania State Route 611 South was closed along the Delaware River. Most of the roads were reopened on the 12th.

Flooding along the Lehigh and Delaware Rivers caused considerable damage along the Lehigh Canal Towpath and the Delaware Canal Towpath into Bucks County. Along the Lehigh River, the damage was caused more by the strength of the current than the crest itself. Along the Lehigh River, in Walnutport a one hundred fifty foot section of a wall collapsed and a half mile section of the towpath was damaged. In Freemansburg, damage was described as worse than what occurred during the 2004 flooding with Ivan. Trail surfaces were washed away and foundations exposed. The river scoured the towpath down to the original clay base from 1828. In Bethlehem, about seventy-five percent of a three mile stretch of the towpath was damaged. There were washouts on two bridges. The Delaware Canal State Park suffered surface damage and washouts and was closed from Easton to Wy Hit Tuk Park in Williams Township. From Wy Hit Tuk Park south to Upper Black Eddy in Bucks County, the trail was passable by foot, but not by bike.

The Delaware River at Easton had moderate flooding. The river was above its 22 foot flood stage from 914 a.m. EST on the 11th through 538 p.m. EST on the 12th. It crested at 26.11 feet at 1245 a.m. EST on the 12th. The Lehigh River at Walnutport (Northampton County) had moderate flooding and was above its 8 foot flood stage from 955 p.m. EST on the 10th through 827 p.m. EST on the 11th. It crested at 12.72 feet at 545 a.m. EST on the 11th. It was the third highest crest on record at Walnutport and the highest crest since August of 1955. Farther downstream, the Lehigh River at Bethlehem had minor flooding and was above its 16 foot flood stage from 713 a.m. EST through 229 p.m. EST on the 11th. It crested at 17.17 feet at 11 a.m. EST on the 11th. Farthest downstream, the Lehigh River at Glendon had major flooding and its highest crest since June of 2006. The river was above its 19 foot flood stage from 426 a.m. EST on the 11th through 1245 a.m. EST on the 12th. It crested at 22.49 feet at 1130 a.m. EST on the 11th.

Event precipitation totals included 4.02 inches in Walnutport, 2.61 inches in Nazareth, 2.60 inches in Plainfield, 2.55 inches in Glendon and 2.21 inches in Martins Creek.

Wider weather episode

For the second time within a week heavy rain fell across Eastern Pennsylvania. An additional 1.5 to 5 inches of precipitation fell and caused more widespread river, stream and poor drainage flooding including the Delaware, Lehigh and Schuylkill Rivers. On average moderate flooding occurred on the Lehigh River, with several locations recording top ten crests. Generally minor flooding occurred on the Delaware and Schuylkill Rivers. Snowmelt in the upper reaches of the Lehigh and Delaware Basins contributed ti the flooding. The worst reported damage was along the towpaths of the Lehigh River in Northampton County and the Delaware River in Bucks County. The heaviest precipitation amounts occurred in the Poconos, while the lightest precipitation amounts occurred in and around Philadelphia. Precipitation started during the late evening of the 9th, fell heavy at times during the daylight hours and evening on the 10th and ended between 3 a.m. EST and 6 a.m. EST on the 11th.

The heavy rain was caused by a low pressure system that moved from the Southern Plains on the morning of the 8th northeast into Iowa on the morning of the 9th, Michigan on the morning of the 10th and into the eastern Great Lakes by the morning of the 11th. This system was able to tap moisture from both the Gulf of Mexico and Atlantic Ocean and lift it over its frontal boundaries. The deep southeast flow was able to enhance the precipitation further over the higher terrain of Eastern Pennsylvania. The rain ended once the low's occluded front moved through Pennsylvania on the 11th.

View location on OpenStreetMap → (40.7500, -75.5800)

Source: NOAA Storm Events Database, event_id 293583. Narrative written by the NWS forecast office that issued the report.