One of the most ecologically and geomorphically significant aspects of all these reference systems is the maintenance of well-drained wave-deposited high salt marsh berm providing topography and vegetation canopies elevated well above Mean Higher High Water (the approximate average elevation of equilibrium tidal marsh platforms deposited by tides alone). Wave deposition of coarse sediment (sand, shell hash, and organic debris) raises substrate elevations up to 1-2 ft above the marsh platform on washovers and berms at reference sites, depending on wave exposure and coarse sediment supply to breaking waves near the marsh edge. The well-drained, elevated washover and berm zone supports taller high marsh vegetation canopies and coarse debris perched on the elevated wave-built salt marsh topography, providing even higher elevation cover for wildlife during extreme high tides as the shoreline retreats.
The role of a nourished coarse high salt marsh berm/washover is important at CMER because of the inevitable loss of high tide cover (vegetation and topography) as the last remnants of the former bayfront levee erode away, and the scarp retreats through a planar marsh platform. Wave deposition is one of the only mechanisms of rapidly forming high salt marsh landforms above Mean Higher High Water. The topography and wide zone of increased vegetation roughness provided by the high salt marsh berm/washover zone also establishes a potentially self-maintaining wave attenuation feature. The self-constructing, self-maintaining high salt marsh berm/washover would, however, be dependent on artificial coarse sediment supply, since there is no modern natural source of coarse sediment delivery to the marsh edge here.