Portland's annual storm tide reaches approximately 11ft 7”, just below the city's 12ft flood stage. Portland experiences these storm surge heights:
25-100 YEAR 4-4.7FT
5-10 YEAR 3FT
ANNUAL 2FT
These storm surge statistics are based on more than a century of water-level observations collected at Portland Harbor and analyzed by the Maine Geological Survey. Together, these records provide a benchmark for understanding how sea level rise will influence future storm tides and coastal flooding along Portland area shorelines.
The following video shows conditions during a typical annual winter storm at the Diamond Cove pier. This event produced a storm tide of 12ft, Portland's flood stage, and was accompanied by a 2–3ft storm surge. The video illustrates the flooding impacts commonly experienced on Great Diamond Island when annual storm tides reach this level. As sea levels rise, annual storms like this will occur on top of a higher baseline water level, increasing the frequency and extent of coastal flooding.
The following video shows conditions during a storm tide of 12ft and a storm surge of 2–3ft. Water levels of this magnitude are typically associated with storms that occur approximately every five years. By 2030, the projected 8” increase in sea level will cause annual winter storms to produce flooding impacts more comparable to the conditions shown here.
To explore how projected sea level rise is expected to influence water levels, tide heights, and annual storm tides at the Geat Diamond Island State pier or in Diamond Cove, tap either of the buttons below.
