RECESSION OF THE POPHAM-SEAWALL BARRIER BEACH COMPLEX, PHIPPSBURG, ME, IN RELATION TO STORM EVENTS AND SEA-LEVEL RISE

The Seawall-Popham complex, located at the mouth of the Kennebec River in Phippsburg, midcoast Maine, is a dynamic, transgressive barrier beach system. In recent years, the migration of two main tidal inlets in the barrier system has played a major role in increased beach erosion at Popham Beach State Park and on the pocket beaches of Cape Small. Changes in the Seawall barrier in recent years have been minimal, however since 2010, landward recession of the frontal dune ridge has become apparent. The purpose of this study is to document physical changes along the barrier complex, pocket beaches and associated tidal inlets, from summer 2012 through winter 2013.

Detailed seasonal and storm-induced changes on the beach system were documented by topographic profile survey, activation rod analysis, high resolution GPS tracks, and time lapse photography. Longer term (annual) changes were documented using high resolution georeferenced satellite imagery and air photographs.

Beach front at Popham Beach State Park has undergone sustained, documented erosion since 2007 when the Morse River migrated towards State Park beaches with the eastward longshore growth of the Seawall Barrier spit. Although the long Seawall spit was breached by avulsion of the Morse River, erosion has continued along the beach front.

Likewise, pocket beaches at Cape Small are continually eroded by the westward shift of the Sprague River, forced against the Cape Small headland by the westward development of the southwestern Seawall spit. Recent changes in the 2.25 km-long Seawall barrier beach are evident with up to 15m of landward migration of the frontal dune ridge in many sectors of the beach since 2009.