The application of geographic information technology and ground-penetrating radar in the study of the evolution of the Charles River basin

A two-part study was conducted on the evolution of the shoreline of the Charles River basin on a city-wide scale as well as in finer detail in Magazine Beach Park, along the Cambridge shore of the river. Both parts of the study utilized geographic information technology (GIT) to integrate and analyze data from modern and historical sources, including maps, digital elevation models (DEMs), and orthographic and oblique photography. The city-scale portion of the study produced estimates of the total area of new land made within the study area since Boston's founding in 1630, 14.3 km2, of which 6.5 km2 was added in the Back Bay area alone. Efforts were also made to quantify the total volume of new land added using the 2002 MassGIS DEM, but that estimate, 30 million m3, was based on somewhat speculative estimates of the original mudflat and salt marsh elevations and is a less robust estimate than those of the surface area. The GIT was also used to display the integrated spatial data in both 2D (map or orthographic view) and 3D (oblique view) to facilitate visualization of historical landscape changes. This technology was also used to produce a 3D time series of landmaking by vertically extruding historical map-based polygon layers in proportion to the length of time between successive layers. This presented a unique opportunity to depict what would normally be shown as a 2D graph of area vs. time instead as a graphic that shows area and time but also shoreline shape at several points in history, thus providing a more full picture of how the basin evolved over time. In addition, the study of Magazine Beach Park centered around a survey-scale 500 MHz ground-penetrating radar exploration of the entire park, which yielded some clues about the park's stratigraphy and recent anthropogenic changes, including the location and extent of the former beach that used to extend half the length of the park. However, the wide spacing of the GPR survey lines and high level of sediment disturbance and fill in some parts of the park limited the success of the survey