Frequent flooding occurs at numerous locations in the Mill Brook drainage basin in Arlington, Massachusetts between the Arlington Reservoir and Lower Mystic Lake caused by run-off from a highly urbanized area coupled with undersized channels and restrictive culverts. Using FEMA funding, the Town of Arlington retained Weston & Sampson to evaluate this tributary to the Mystic River by developing a detailed hydrologic/hydraulic model of the 5.75-square-mile watershed to analyze and evaluate flood protection scenarios.
Weston & Sampson evaluated a variety of alternatives to provide 25-year flood protection for repetitive loss properties and reduce peak runoff to the entire Mill Brook corridor. Alternatives included green infrastructure, detention, and traditional gray infrastructure. We also conducted a walking stream survey where we documented existing conditions using GPS, photographs, and mobile data collection. Our approach produced a thorough understanding of Mill Brook including:
- Locations requiring brush trimming and debris removal
- Locations where yard waste was being improperly disposed
- Sediment depths and volumes along the full alignment
- Identification of new MS4 outfalls along with a dry weather screening
- Condition assessment of all accessible culverts
- Cross sections every 50 feet to improve modelling accuracy
- Installation of nine pressure transducers to measure flow depth for base flow and model calibration
- Electronic capture of all data
- Detailed updates to existing stormwater GIS
- More than 3,500 georeferenced photos of Mill Brook features along its 3.5-mile length
Our comprehensive data was useful not only for accurate modeling of Mill Brook and planning for future projects, but also to support ongoing operation and maintenance activities.