Shoreline Situation Reports (SSR) were first generated by VIMS in the 1970's to report the condition and status of the shore lands. The SSR series was published in hardcopy on a county by county basis for each Tidewater Virginia locality. The reports were intended to assist planners, managers, and regulators in decisions pertaining to management of coastal areas and natural resources therein. This Shoreline Inventory report continues a process which updates and expands the earlier reports. Data collected reports conditions surveyed in the immediate riparian zone, the bank, and along the shoreline.
To inventory Virginia's tidal shoreline condition.
There are three shapefiles that are part of the Gloucester County Shoreline Inventory database: glou_lubc, glou_astru, glou_sstru. Glou_lubc (land use and bank cover for Gloucester County) is a linear shapefile containing data about land use, bank height, erosion, and marsh and beach status along the shoreline. Glou_sstru (Gloucester County shoreline structures) is a linear shapefile delineating hard structures in place for shoreline protection (breakwater, bulkhead, dilapidated bulkhead, groinfield, jetty, marina, miscellaneous, and riprap). Glou_astru (Gloucester County structures) is a point shapefile with locations of docks, ramps, and boathouses. The attributes of these three shapefiles are explained in the Entity and Attribute Information section below.
ground condition
These data should not be used for jurisdictional permit determinations beyond providing general shoreline condition or status information. These data have not been surveyed to property boundaries.
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The attributes were compared to original GPS data logs for accuracy. Errors were corrected where noted. Attributes were updated and/or added based upon visual inspection of the 2002 Virginia Base Map imagery.
Chain-node topology present. Linear coverages were built for line and point coverages were built for points.
All Gloucester County shoreline that has a minimum depth of 2 feet at mean low water was surveyed. Some shorelines are coded remotely if access was restricted due to depth.
Shoreline conditions were recorded with a GPS unit as the boat moved along the shoreline. Data were transferred from the GPS boat track to an existing digital shoreline coverage by projecting data to the shoreline at a 90 degree angle from the boat track. High resolution orthophotography was used as background imagery to aid in data positioning. Dock and boathouse point data were aligned with docks on the images. Land use features were placed along the shore so changes in land use were coincident with changes illustrated in the imagery. Positional accuracy for data that has been corrected with imagery is .3 meters (equivalent to image resolution). Data not visible on the imagery (bulkheads, riprap, etc.) has a positional accuracy of 11 meters. Accuracy was determined by comparing digitally processed data locations to onsite GPS ground surveys collected at random.
Used to position land use and cover data. Used to create a new digital shoreline for Gloucester County in 2003. This shoreline serves as the base shoreline for the Gloucester Shoreline Inventory data.
Imagery serves as a background in the map portfolios. Imagery is used to update land use and structure data as well as to remotely coded areas not surveyed in the field. Imagery used to adjust digital shoreline.
Data were collected by a two-person field crew using hand-held GPS units and navigating along the shoreline in a shoal draft boat. Features collected include land use, bank height, presence of marsh or beach, shoreline stability, riprap, marinas, breakwaters, bulkheads, groinfields, miscellaneous, jetties, docks, boat ramps, and boathouses. Point features were surveyed with a ten second observation recorded at 1 reading/second. Linear features were surveyed kinematically at a rate of one observation every 3 seconds.
Data from the GPS units were postprocessed on a PC with Trimble Pathfinder Office software. Postprocessing includes differential correction using base station data collected at the VIMS laboratory. Corrected data is converted to ArcInfo coverages and transfered to a UNIX workstation for further processing.
Using ArcInfo and ERADAS Imagine in the UNIX environment, a new base shoreline was created by digitizing the land-water interface illustrated on the DOQQs. Gloucester County boundary (determined from the USGS DLG digital dataset (1990)) set the limits for Gloucester shoreline.
In the UNIX ArcInfo environment, boat-track "arcs" and "points" representing erosion control structures and docks, boathouses, and ramps were manually corrected to the base shoreline (DOQQ). Points were moved to locations on the shoreline perpendicular to the original locations on the boat-track. Points were coded and the access structures (astru) were visually checked for attribute accuracy between coded shoreline and boat-track data. DOQQ imagery was used to validate point locations that could be seen on the imagery (e.g. docks and boathouses).
Land use data was transferred from the boat-track "arcs" to the base shoreline (DOQQ) in 2005 using shapefiles in the ArcMap environment. Arcs were split and moved to locations on the shoreline perpendicular to the original locations on the boat-track. Shoreline arc segments were coded, and the shapefiles were visually checked for attribute accuracy between coded shoreline and boat-track data. VBMP 2002 imagery was used to validate arc locations that could be seen on the imagery (e.g. riparian land use).
Using ArcMap, the VBMP 2002 imagery was used as a data source to code shoreline in areas inaccessible by boat due to water depth. Imagery was suitable for coding not all, but certain features such as land use, docks, boathouses and some erosion control. These "remote" coded areas were given the item REMOTE = 'yes' to distinguish them from data collected in the field using GPS.
Areas surveyed prior to image collection could be updated using the high resolution 2002 VBMP imagery in the background. Certain features and attributes such as land use and structures could be detected and therefore digitally checked and updated as a quality control measure. Using ArcMap 9.2, docks, boathouses, boat ramps, and some erosion control structures constructed after the original survey were digitized and coded as item REMOTE = 'yes' to distinguish them from data collected in the field using GPS.
A portfolio containing thirty-four 1:12,000 scale plates was created for Gloucester County. Each plate shows three maps: riparian land use, bank and buffer conditions, and shoreline features. VBMP 2002 imagery is displayed in the background to provide users with additional information. An additional four maps have been created to show the location of remotely coded land use and structures.
Metadata imported.
Internal feature number.
ESRI
Feature geometry.
ESRI
Point features that include structures used in accessing and observing the water.
coded in the lab using background imagery
date of GPS survey
Two other shapefiles combine with _astru to complete the Gloucester County Shoreline Inventory. The complete set includes _lubc, _astru, and _sstru. Attributes in the _lubc file include: FEATURE or land use which may contain the following values: agriculture, commercial, forest, grass, paved, residential, scrub-shrub, timbered, and unknown; HEIGHT is the bank height with 0 - 5 feet, 5 - 10 feet, and 10 - 30 feet; EROSION or bank erosion can have the values: low or high; MARSH values are Yes(Erosion), Yes(No_Erosion), No, or a blank field; BEACH defines the presence and condition of the beach: Yes(Eroding), Yes(No_Erosion), No, or blank field; and REMOTE refers to data gathered remotely: a blank value indicates the data was collected with the GPS unit, a "y" indicates that the shoreline attributes where determined from the DOQQ or 2002 VBMP imagery. Attributes in the _astru (access structure shapefile) are: PNTSTRUC contains access structures such as boathouse, dock, or ramp; and REMOTE. Attributes found in the _sstru shapefile are: STRUCTURE (erosion control) with values such as breakwater, bulkhead, groin, jetty, marina, and riprap; and REMOTE.
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The Comprehensive Coastal Inventory Program (CCI) at VIMS performs a service by distributing data generated by either CCI or public agencies which offer data without restriction or charge. CCI assumes no responsibility for data accuracy or precision, metadata completeness or correctness for digital information. CCI assumes no liability for misuse of any data which may arise as a result of any alteration, conversion, or combination with other data sources. As well, the timeliness and scale of these products must be considered when evaluating appropriate use.
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