Seawall
The seawall at Dog Green Sector of Omaha Beach was a four to twelve foot high wood and concrete wall constructed just behind the beach's shingle. Behind the seawall ran a paved road that ran from beach exits code-named Dog One and Dog Three.
Although originally designed by the French as a means of protecting parts of the beach from erosion, the seawall also provided attacking American troops with some measure of protection during the D-Day assault. As part of their beach defenses, the Germans reinforced the seawall with barbed wire and mines.
Fact vs. Fiction
The seawall shown in the film is not accurate, and resembles more of a sand dune than a concrete wall. Although dunes may have been present at certain parts of Omaha Beach, the seawall covered virtually all of Dog Green Sector. The shingle (smooth stones deposited by the tides) and paved road are not depicted in the movie.