A computer-based shoreline mapping methodology, within the framework of a geographic information system, was used to compile and analyze changes in historical shoreline position and island area between 1847/49 and 1986 for the Mississippi Sound barrier island system. The data base consisted of three to four cartographic shorelines and one to two air photo interpreted shorelines. The dominant direction of movement for Dauphin, Petit Bois, Horn, and Ship islands is to the west, whereas cross-shore change in shoreline position is the primary mechanism by which the beaches on Cat Island respond to incident processes. Average shoreline change for the study area was about -1.7 m/yr; however, Horn Island illustrated no net shoreline change for the period of record and the western halves of Petit Bois and Ship islands were net progradational. Although spatial variability in shoreline movement was common, associated land loss was relatively consistent, ranging from -1.6 to -2.5 ha/yr.
The magnitude of lateral island migration is generally an order of magnitude greater than cross-shore movements. East of Dog Keys Pass, the islands are moving to the west by updrift erosion and downdrift accretion at rates exceeding 30 m/yr. The eastern end of Petit Bois Island illustrates the greatest lateral movement, averaging 89.9 m/yr between 1848 and 1986. Long-term changes recorded for the ends of Ship Island are significantly smaller, mainly due to dredging at the Biloxi navigation channel and distance from sand source, limiting the quantity of sand available for natural bypassing to the west. Short-term lateral migration trends illustrate a similar response at Horn Island Pass.
The purpose of the Louisiana Coastal Geographic Information System Network (LCGISN) is to identify and capture geographical material and consolidate it into an easily retrievable form, despite different formats, hardware platforms, software, and storage methods. This will enable individuals to receive information traditionally unavailable. The network uses a distinctively different approach for identifying and dispensing geographic information and is not limited to a single medium. It is designed to link all data mediums into a coherent structure for sharing geographically referenced information. Linking original programming with existing GIS software and an industry standard relational database management system will provide users the capability to search for data references by interactively denning an area of interest on a digital base map. Several agencies will have access through the network to a wide variety of information.Numerous decisions have been made concerning the user community's ability to search for data references by interactively denning the area of interest. To provide this function, menus are being developed for specifying data format conversions, projection and datum transformations, and storage and retrieval of several of the most commonly used coastal data sets. The 65 menus under development will allow the user to set search criteria by selecting parameters from a series of menu-driven options. The system will return any, or all of the following: a list of digital maps or imagery that can be displayed, a list of maps or remotely sensed data and information on their availability, and a list of bibliographic references concerning the area and subject defined.
This report was prepared under contract to the U J9. Geological Survey and USGSedftorialstandaidsorwiththeNorthAmerieanStratig do not nsessMrily represent thoee of the USGS. Any use of tr only and does not unply endorsement by the UJS. Government. not been reviewed for conformity with Opinion* and conclusions expressed herein e, product, or firm name* it for descriptive purposes
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