Cambridge, MA Environmental Rules: Flood Elevation Requirements (2026)

Section 22.83.1(a) directs the City Engineer to promulgate, and periodically revise, projected flood elevations for every lot in Cambridge, called Long-Term Flood Elevations (LTFEs). Under Section 22.83.1(b), precipitation-driven LTFEs come from the city's own hydraulic model, while sea level rise and storm surge LTFEs are based on climate modeling performed or endorsed by Commonwealth of Massachusetts agencies. Section 22.83.1(c) sets the projection window at roughly 50 years, so elevations set around 2020 anticipate flood conditions around 2070, and each promulgation must state its projected timeframe.

LTFEs are expressed in vertical feet relative to the Cambridge City Base (CCB) datum (Section 22.83.1(d)) and published as parcel-level data tables plus a digital "FloodViewer" map (Section 22.83.1(e)); a licensed surveyor's property survey is treated as more accurate than the city's LIDAR-based ground elevation data, though it cannot change the LTFE itself. New or revised LTFEs must be open for public comment at least 90 days before final promulgation (Section 22.83.1(f)). Section 22.83.2(a) defines two applicable standards, the 1%-Probability LTFE and the 10%-Probability LTFE, and Section 22.83.2(b) grandfathers a development that already has a DPW-approved LTFE plan against later, stricter LTFEs, so long as it proceeds continuously to completion.

Section 22.82 applies these flood standards to development already covered by the Green Building Requirements of Section 22.20 and to other development identified elsewhere in the Zoning Ordinance.