Marsh migration land use inferred from historical T-Sheets of the Chesapeake Bay

Detailed methods are listed in the associated publication (Schieder et al., 2018 https://doi.org/10.1007/s12237-017-0336-9). Briefly, we compared the spatial distribution of marshes in nineteenth-century maps to modern aerial photographs for the areas included in 40 NOS topographic sheets ("T-sheets") that included information on simple land types (e.g., marsh, farmland, forests) from the tidal portions of the Chesapeake Bay. Tidal marsh extent was digitized by hand by tracing the boundary between marsh and open water and the boundary between marsh and upland. The marsh-forest boundary was identified as the line between the dense tree canopy and marsh, the marsh-agriculture boundary was identified as the line between agriculture and marsh, and the marsh-water boundary was identified as the line between open water and adjacent land excluding beaches. The areas of agricultural land converted to marsh, forestland converted to marsh, and total upland conversion to marsh were summarized for each T-Sheet.