This particular marsh is slowing shifting from wetland marsh to non wetland marsh as soil accumulates and vegetation builds up. The grassy swath along the outer edge is growing on piles of very old drift wood.
A review of historic aerial images shows that many of the along shore marshes of Port Discovery have accumulated large batches of driftwood from past high tides combined with storm surges. Some of the driftwood deposits are over 50 years old and date back to a particularly high tide storm surge event in the 1960s or an even larger and older one in the 1950s. These events caused flooding at low beach areas with lined with homes and hence were recorded in newspapers.
Tidal surge flooded Becket Point in Port Discovery
There may be some other factors regarding wood deposition. One might be the availability of drift wood along the shore. This image of the upper end (south) of the bay suggests a source of driftwood that is not so common today as it once was.
Upper Port Discovery and log rafts.