Officials are closely monitoring other river sites across New Jersey, but say the water levels should be going down Thursday afternoon. Watch video
The Millstone River in the Griggstown section of Franklin Township overflowed Thursday morning as heavy rain and melting snow combined to push the river over its flood stage, forcing the closure of the Griggstown Causeway and the Blackwells Mills Causeway.
Franklin Township police confirmed the closures Thursday morning on its social media pages and advised drivers to "seek alternate routes and expect delays in the area."
Flood maps monitored by the National Weather Service, which show how high the water level is based on gauges along the river, indicated the Millstone River rose to 12.2 feet as of 10 a.m., which is more than two feet above flood stage.
Once the level rises to 9.5 feet, the Griggstown Causeway is normally shut down, and when it rises to 10 feet River Road in Montgomery Township usually starts to flood near the Griggstown Causeway.
The Blackwells Mills & Griggstown Causeways are both closed due to flooding. Seek alternate routes and expect delays in the area.
Posted by Franklin Township Police Department - Somerset County on Thursday, February 4, 2016
As of late Thursday morning, two other river sites across the state were getting close to overflowing, according to the weather service maps:
- The Millstone River in Millstone Township was just one foot away from its flood stage of 10 feet as of 10 a.m. If the river rises to 10 feet, River Road is subject to closure between Yorktown and Amsterdam, and Canal Road usually gets flooded near Suydam Road.
- The Raritan River in Manville was 2 feet away from its flood stage of 14 feet as of 10 a.m. If the river rises to 14 feet, street flooding in Manville would become widespread.
More snow? N.J. could get up to 4 inches Friday morning
However, the weather service is expecting the water levels in the Millstone and Raritan rivers to start going down as the afternoon progresses, said Jim Bunker, at the weather service's regional office in Mount Holly.
A strong storm system that moved through New Jersey on Wednesday dropped between a half-inch and 1.5 inches of rain, with the heaviest amounts recorded in Morris, Somerset, Hunterdon and Passaic counties.
While those amounts are not substantial, extra runoff into streams and rivers was generated by melting snow from the January blizzard.
Aside from the towns listed in the chart, these locations came close to getting 1 inch of rain Wednesday into early Thursday: Mansfield, White Township and Mine Hill, each with 0.99 inches; Washington Township in Morris County, with 0.98 inches; Boonton, with 0.97 inches; and Jefferson and New Providence, each with 0.96 inches, according to data compiled by the Community Collaborative Rain, Hail and Snow Network.
Len Melisurgo may be reached at LMelisurgo@njadvancemedia.com. Follow him on Twitter @LensReality. Find NJ.com on Facebook.