Development of Historical Topographic Models of the Beach/Dune System in Northeast Coastal and Barrier Network Parks

Hapke, Cheryl

The USGS Patuxent Wildlife Research Center Coastal Field Station, located at the University of Rhode Island, in collaboration with the Northeast Coastal and Barrier Network (NCBN) of the National Park Service (NPS), recently completed a study to develop a baseline of historical topography to be utilized in long-term topographic change analyses in four coastal National Parks in the Northeast U.S; Fire Island National Seashore (FIIS), Cape Cod National Seashore (CACO), Gateway National Recreation Area (GATE), and Assateague Island National Seashore (ASIS) (Figure 1). The dynamic nature of coastal barriers is a defining characteristic influencing nearly every aspect of their ecology. Fundamentally disturbance driven systems, barrier islands and their endemic biota are continually shaped by physical forces on much faster time scales compared to mainland systems. Because of the rapid pace and scope of change, long term monitoring is crucial towards understanding natural barrier island conditions as well as anthropogenic influences. The historical topographic models produced for this project will provide baseline information for incorporation into analyses that will further the understanding of the potential impacts of sea-level rise and increased storminess to the coastal parks. The most fundamental knowledge required for understanding how coastal systems may behave in the future is how they have behaved in the past. Historical shoreline change data exist for most areas, but analyses of such data are restricted to 2-dimensional assessments of a line near water level on the beach, thus providing little information on the back beach and dune areas. The 3-dimensional models developed for this study can be integrated with modern topographic data, such as lidar, to measure volumetric change. The photogrammetric products generated for this project are the only available source of historical topographic data for these areas, and include not only historical digital terrain models but also the generation of historical orthophotographs. Historical aerial photography for each park was obtained from agencies such as the U.S.National Archives, NOAA, USGS, and other local and state agencies. Aerial photographs were chosen for each park to provide the oldest possible topographic database, while maintaining an acceptable accuracy. The dates of the photography chosen for each park are: FIIS, 1969; CACO, 1951; GATE, 1953; and ASIS, 1976. In order to maintain a pixel resolution and vertical accuracy of 0.50 m or less, all imagery has a nominal scale of 1:12000 (see Hapke, 2005; Hapke and Green, 2005) and was scanned (converted from film to digital) at resolutions >1200 dpi. The photographs are obtained as film diapositives to minimize errors associated with distorted media.

Development of Historical Topographic Models of the Beach/Dune System in Northeast Coastal and Barrier Network Parks

Program

Products

Collections