Virginia Institute of Marine Science
Shore Evolution in Four Virginia Localities
Project Description as Proposed:
As part of the multi-year dune project, shore evolution has been documented in many localities in the Virginia portion of Chesapeake Bay. These data sets have been useful in a variety of ways. They have shown the rates and patterns of shore change through time at Virginia's estuarine dunes. They have also been useful to many other research projects and advisory service activities at VIMS and other agencies. Orthorectification of historic and recent aerial photography and digitization of the shoreline show the geomorphic evolution of the coastal zone in terms of shoreline change and landuse as well as nearshore variations in sandbars and shoals where present. We propose continuing this process for Counties of Gloucester, York, Poquoson, and the City of Newport News. Gloucester and York already have some dates and/or portions of their shoreline analyzed with historical aerial photography due to other projects.
These shore evolution reports will provide critical data on which future shoreline management plans should be based. In addition the shoreline land use data will show local planners and decision makers how shoreline use has evolved, which may help predict future land use patterns.
Scott Hardaway, (804) 684-7277; firstname.lastname@example.org
10/01/08 - 9/30/09; Projects Completed
Final Product Received:
Project Summary Provided by Grantee:
The shorelines of four localities, Gloucester, York, Poquoson, and Newport News, in Virginia were analyzed for change. Historical and recent aerial photos were orthorectified for each locality and the shoreline digitize. Photo dates mosaicked for Gloucester are 1937, 1953, 1960, 1968, 1978, 1994, 2002, and 2007. York, Poquoson and Newport News photo mosaics are dated 1937, 1953, 1963, 1994, 2002, and 2007. York also had 1937, 1963, 1994, 2002, and 2007, but the 1953 date was not complete because the military blacked out the images due to the presence of a military base during the Korean War.
The low water shoreline was digitized on the photos. These evolution reports include all the smaller rivers and creeks for the locality. This presented challenges to the methodology in that areas where very little change is occurring or have heavy vegetative cover introduced a fair amount of uncertainty into the data. As such, in some areas, it was determined that the intervening shorelines provided no additional information and therefore were not digitized. The photos, however, are available.
In as many reaches as possible, a baseline was created about 60 meters offshore with transects 10 meters apart. The Digital Shoreline Analysis Software (DSAS) program was used to determine the End Point Rate (EPR) between 1937 and 2007 and the Linear Regression Rate (LRR) for those dates and any intervening shoreline dates available. Concerns that the LRR was not significantly different from zero for each transect led VIMS staff to perform a two-tailed t-test. If the LRR was determined to be not significantly different from zero, it was not plotted on the shore change maps. In Gloucester 41% of the transects did not pass the t-test indicating that the calculated LRR was not significantly different from zero. In York, Poquoson, and Newport News, the percentages of transects that did not pass the t-test were 59%, 23%, 34%.
These data indicate that along some individual transects, the LRR may provide better information than the EPR; however, locality-wide and in individual subreaches, this was not the case. In addition, the LRR along many transects could not reliably be used in all shoreline situations as could the EPR. So, in these localities, the EPR is a reliable indicator of shoreline change rates even when intervening dates are available.
The digital reports are available on the VIMS, Shoreline Studies Program website at http://web.vims.edu/physical/research/shoreline/Publications-Dune.htm
under Chesapeake Bay Dune Evolution Reports. Since the reports are expensive to print, only a limited number of printed reports are available. Each locality was sent a printed and digital copy.
Disclaimer: This project summary provides the federal dollars initially awarded to the grantee. Due to underexpenditure or reprogramming of grant funds, this figure may change. For more information on the allocation of coastal grant funds, please contact Laura McKay, Virginia Coastal Program Manager, at 804.698.4323 or email: Laura.McKay@deq.virginia.gov
A more detailed Scope of Work for this project is available. Please direct your request for a copy to Virginia.Witmer@deq.virginia.gov