Most of these maps are drawn from an EPA study, which developed county-scale elevation
maps to illustrate vulnerability to sea level rise
, using existing data--including 2-ft contour data provided by the City of Philadelphia. The maps show elevations
relative to spring high water
, the average tide during new and full moons. The accuracy of the data varies, so we have
also included an index map showing the data sources, which can help you figure out how accurate
our maps are for a particular location.