Friday’s rain set a record at Logan Airport, and in Chelsea it landed on the one block the city has listed for more than a decade as a place where water has nowhere to go. Willow Street was closed Friday night while first responders helped drivers get their cars out of the floodwater, WHDH reported.
The National Weather Service measured 2.64 inches of rain at Logan on Friday, November 6. That is a record for the date, beating the 1.58 inches that fell on November 6, 1966. A normal November 6 brings about a tenth of an inch.
The worst of it came right before high tide
Hourly readings from the airport weather station show the rain building through the evening: about 0.30 inch in the hour ending just before 7 p.m., another 0.29 inch by 8 p.m. and 0.52 inch in the hour ending at 8:54 p.m. That is more than an inch in three hours.
High tide in Boston Harbor was predicted for 9:13 p.m., at 9.64 feet above the low water mark, according to NOAA. On Willow Street, that timing matters.
What the city’s own plan says about Willow Street
Chelsea’s 2014 Hazard Mitigation Plan names “Willow Street between Congress and Maverick Streets” as one of the city’s locally identified flooding areas. The plan describes it as “a low elevation area where fresh water runoff is unable to drain due to high tide and surge blocking the storm drain.” In other words, when the harbor is high, the rain falling on the street has no way out until the tide drops.
The plan’s recommended fix was a new pump station, with an estimated cost of $2 million to $3 million. It listed the project among its mitigation goals as “Correct flooding in the Willow Street neighborhood: install new pump station.” The plan said the flooding there did not reach homes, though it noted the problem could affect redevelopment nearby. No later city document reviewed for this story says whether that pump station was built.
The block is also home to the Boys and Girls Club at 30 Willow Street, which the city has named as the center of its Cool Block Initiative, a project aimed at summer heat in that neighborhood.
The city’s largest flood project is elsewhere, on the Island End River near the produce market, and it lost the $50 million federal grant that was going to pay for construction. That barrier is built for coastal storm surge, not for rain backing up behind a high tide on an inland street.
Chelsea was not alone
Part of Memorial Drive in Cambridge was also closed for flooding Friday night, and several cars were towed after stalling out under the Longfellow Bridge, according to WHDH.
What comes next
The weather service forecast for Chelsea calls for rain showers and patchy fog Saturday morning, with another quarter to half inch of rain possible, then a chance of showers again Saturday night with up to a quarter inch more. Saturday night’s high tide is predicted for 10 p.m. at 9.59 feet. Sunday is expected to be mostly sunny with a high near 59 and gusty west winds.
The city usually posts closures on its Facebook page and through its alert system. If you have to drive through low spots Saturday night, the same rule applies as Friday: do not drive into water when you cannot see the road. Our September guide to high tides and flood warnings lists the other low spots that flood when the harbor is high.
The year as a whole is still dry. Even with Friday’s record, Logan has recorded 27.63 inches of rain since January 1, about 8.7 inches below normal.