There is a long history of Alewife Brook flooding during rain storms. Alewife Brook flooding occurs because of its
topography and because of urbanization. The area is relatively flat and has been heavily developed with impervious surfaces like pavement and buildings. This results in a reduction of natural flood storage.
The urban stormwater drainage system is designed to handle limited, small-size storms.2
When we get larger or more intense storms, there is flooding.
2023 FLOOD EVENTS
We have documented that Alewife Brook flooded at least 5 times in 2023. It is possible that more flooding occurred. But based on photographic evidence and confirmed with USGS water gage data, we know of at least 5 times.
In these 2023 storms, sewage-contaminated flood water covered parts of the Alewife Greenway. The Greenway is a popular multi-use path on State Parkland for walkers, joggers, students, and cyclists. The Alewife Greenway connects residents from Somerville, Medford, Cambridge, and Arlington to the Alewife MBTA Station and the Minuteman Bikeway.
What level of storm caused this flooding?
The daily rainfall on all five documented 2023 flood dates ranged from 1.33 to 2.54 inches. For comparison, NOAA Atlas 14 puts the Boston 1-year, 24-hour storm at 2.53 inches and the 2-year, 24-hour storm at 3.14 inches.
Not one of these events reached even a 2-year storm, and four of the five were well below a 1-year storm. Alewife Brook flooded with sewage in the floodwater at rainfall levels that occur multiple times a year.