Flash Flood and Flood in New Jersey, October 8 to 10, 2005

The combination of a very slow moving cold front and copious moisture from the remnants of Tropical Storm Tammy produced periods of very heavy rain across Somerset County during the morning and evening of the 8th. The evening period of very heavy rain caused many of the smaller creeks and brooks to flood in the county. Flooding later spread into the Raritan and Millstone Basins. Storm totals averaged five to nine inches. In Hillsborough Township, an apartment building was evacuated after its basement was flooded with seven feet of water. In Montgomery Township, firefighters rescued six people from three flooded roadways during the evening of the 8th including a family of four whose vehicle was surrounded by the flooding Bedens Brook. A bridge over the Raritan River between Branchburg and Bridgewater Townships was closed. The North Branch of the Raritan River at North Branch was above its 12.3 flood stage from 1253 a.m. EDT through 904 a.m. EDT on the 9th. It crested at 14.02 feet at 5 a.m. EDT. Farther downstream, the North Branch of the Raritan River at Raritan was above its 10 foot flood stage from 240 a.m. through 950 a.m. EDT on the 9th. It crested at 10.9 feet at 615 a.m. EDT. Farther downstream at the village of South Branch, the North Branch of the Raritan River was above its 7 foot flood stage from 1057 p.m. EDT on the 8th through 151 p.m. EDT on the 9th. It crested at 9.99 feet at 1045 a.m. EDT on the 10th. Along the main stem of the Raritan River at Manville, the river was above its 14 foot flood stage from 811 a.m.EDT through 458 p.m. EDT on the 9th. It crested at 15.44 feet at 1 p.m. EDT. Farther downstream at Bound Brook, the Raritan River was above its 28 foot flood stage from 9 a.m. EDT through 608 p.m. EDT on the 9th. It crested at 29.20 feet at 230 p.m. EDT. The Millstone River at Griggstown was above its 10 foot flood stage from 10 p.m. EDT on the 8th through 4 p.m. EDT on the 10th. It crested at 15.13 feet at 530 a.m. EDT on the 9th. Farther downstream at Blackwells Mills, the Millstone River was above its 9 foot flood stage from 457 a.m. EDT on the 9th through 155 a.m. EDT on the 10th. It crested at 11.05 feet at 1033 a.m. EDT on the 10th. Just before its confluence with the Raritan River, at Weston, the Millstone River was above its 12.4 foot flood stage from 1229 p.m. EDT through 4 p.m. EDT on the 9th. It crested at 12.5 feet at 1 p.m. EDT. The Green Brook at Plainfield (Union County) was above its 8 foot flood stage from 115 a.m. EDT through 749 a.m. EDT on the 9th. It crested at 9.12 feet at 545 a.m. EDT. Pike Run in Belle Mead was above its 7 foot flood stage from 913 p.m. EDT on the 8th through 341 a.m. EDT on the 9th. It crested at 9.83 feet at Midnight EDT on the 9th. Peters Brook in Somerville was above its 8.2 foot flood stage from 1025 p.m. EDT on the 8th through 1235 a.m. EDT on the 9th. It crested at 9.2 feet at Midnight EDT on the 9th. Storm totals included 8.87 inches in Pottersville, 7.80 inches in Branchburg, 7.52 inches in Martinsville, 7.08 inches in Hillsborough, 6.94 inches in Somerville, 6.91 inches in Far Hills, 6.88 inches in Belle Mead and 6.00 inches in North Plainfield. The flooding on the 8th and 9th and the subsequent flooding during the upcoming week damaged over 2,700 single family homes, over 640 apartment units and 220 businesses throughout the state of New Jersey. The cold front moved from near Pittsburgh, Pennsylvania at 8 p.m. EDT on the 7th, to the Susquehanna Valley in Pennsylvania at 2 a.m. EDT on the 8th, to the Poconos and Berks County in Pennsylvania and just west of Chesapeake Bay in Maryland at 8 a.m. EDT on the 8th. The cold front stalled as waves of low pressure road northeast along it. At 2 p.m. EDT on the 8th, the cold front just edged into northwestern New Jersey and the Philadelphia northwest suburbs and was still west of Chesapeake Bay in Maryland. At 8 p.m. EDT that evening the cold front barely moved into the Philadelphia New Jersey suburbs and the Delmarva Peninsula. The cold front and waves of low pressure cleared the Delaware and New Jersey coasts between Midnight EDT and 2 a.m. EDT on the 9th. The slow movement and stalling coupled with an unstable air mass and tropical moisture associated with Tammy helped enhance the torrential downpours. The flooding would have been even worse if not for the unseasonably dry weather that preceded this event from the middle of August.