Entity_Type:
Entity_Type_Label: VA_rates_ST.shp Attribute Table
Entity_Type_Definition:
Rates of short-term shoreline change are calculated by DSAS and stored in the transect file, using the distance measurements between shorelines and baseline at each DSAS transect. Short-term date range covers only lidar based, mean high water shorelines and therefore no bias was applied. The shapefiles will have ST for short-term in filename.
Entity_Type_Definition_Source: U.S. Geological Survey (USGS)
Attribute:
Attribute_Label: FID
Attribute_Definition: Internal feature number.
Attribute_Definition_Source: Esri
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: Shape
Attribute_Definition: Feature geometry.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain: Feature geometry. Rates are polyline shapefiles.
Attribute:
Attribute_Label: BaselineID
Attribute_Definition:
Unique identification number of the baseline segment. If BaselineID=0 no transects will be generated. Used by DSAS to determine transect ordering alongshore if multiple baseline segments exist.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 2
Range_Domain_Maximum: 14
Attribute:
Attribute_Label: GroupID
Attribute_Definition:
This optional field is a way to aggregate transects on the basis of physical variations alongshore (for example, tidal inlets, change in coastal type, or hard stabilization features). This value was assigned by the user as an attribute to a baseline segment and results in a group average being reported in the DSAS summary text file.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 2
Range_Domain_Maximum: 8
Attribute:
Attribute_Label: TransOrder
Attribute_Definition:
Assigned by DSAS based on ordering of transects along the baseline. Used to allow user to sort transect data along the baseline from baseline start to baseline end.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 494
Range_Domain_Maximum: 3360
Attribute:
Attribute_Label: Azimuth
Attribute_Definition:
Assigned by DSAS to record the azimuth of the transect measure in degrees clockwise from North. If a transect position has been adjusted during the editing process, the azimuth value in the attribute table is updated automatically.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 23.78
Range_Domain_Maximum: 355.56
Attribute:
Attribute_Label: ShrCount
Attribute_Definition: Number of shorelines used to compute shoreline change metrics.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 2
Range_Domain_Maximum: 3
Attribute:
Attribute_Label: TCD
Attribute_Definition:
The Total Cumulative Distance (TCD) is the measure in meters along shore from the start of the baseline segment with an ID=1, and measured sequentially alongshore to the end of the final baseline segment
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 27957.64
Range_Domain_Maximum: 217385.29
Attribute:
Attribute_Label: EPR
Attribute_Definition:
The end point rate (EPR) is calculated by determining the distance between the oldest and youngest shoreline on a DSAS transect and dividing by the time elapsed between the two shoreline dates.Decimal values may be positive or negative, which is used to indicate landward (negative) or seaward (positive) direction from baseline origin. Reported in meters per year.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: -44.3
Range_Domain_Maximum: 32.07
Attribute:
Attribute_Label: EPRunc
Attribute_Definition:
An estimate of end point rate uncertainty. The shoreline uncertainties for the two positions used in the end point calculation are each squared, then added together (summation of squares). The square root of the summation of squares is divided by the number of years between the two shorelines.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.19
Range_Domain_Maximum: 1.21
Attribute:
Attribute_Label: LRR
Attribute_Definition:
A linear regression rate-of-change (LRR) statistic was calculated by fitting a least-squares regression line to all shoreline points for a particular transect. Any shoreline points that are referenced to HWL were adjusted by the proxy-datum bias distance (meters) along the transect to correct for the offset between proxy-based HWL and datum-based MHW shorelines. The best-fit regression line is placed so that the sum of the squared residuals (determined by squaring the offset distance of each data point from the regression line and adding the squared residuals together) is minimized. The linear regression rate is the slope of the line. The rate is reported in meters per year with positive values indicating accretion and negative values indicating erosion. LRR calculations require a minimum of 3 shorelines; less than 3 shorelines results in a “null” value, which is not a supported value in shapefile format. A value of 9999 in the LRR attribute field along with a ShRCount of 2 indicates the required number of shorelines to compute the linear regression rate was not met.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: -1.83
Range_Domain_Maximum: 5.58
Attribute:
Attribute_Label: LR2
Attribute_Definition:
The R-squared statistic, or coefficient of determination, is the percentage of variance in the data that is explained by a regression. It is a dimensionless index that ranges from 0.0 to 1.0 and measures how successfully the best-fit line accounts for variation in the data. The smaller the variability of the residual values around the regression line relative to the overall variability, the better the prediction (and closer the R-squared value is to 1.0). A value of 9999 in the LR2 attribute field along with a ShRCount of 2 indicates the required number of shorelines to compute the linear regression rate was not met.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.0
Range_Domain_Maximum: 1
Attribute:
Attribute_Label: LSE
Attribute_Definition:
This quantity is the standard error of the regression, also known as the standard error of the estimate. To calculate it, the distance between each data point and the regression line is calculated. These distances are squared then summed. The sum is divided by the number of data point minus two. The square root is taken of the result. A value of 9999 in the LSE attribute field along with a ShRCount of 2 indicates the required number of shorelines to compute the linear regression rate was not met.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.01
Range_Domain_Maximum: 27.74
Attribute:
Attribute_Label: LCI90
Attribute_Definition:
The 90 percent confidence interval (LCI90) is calculated by multiplying the standard error of the slope by the two-tailed test statistic at the user-specified 90 percent confidence. This value is often reported in conjunction with the slope to describe the confidence of the reported rate. For example: LRR = 1.2 and LCI90 = 0.7 could be reported as a rate of 1.2 (+/-) 0.7 meters/year. A value of 9999 in the LCI90 attribute field along with a ShRCount of 2 indicates the required number of shorelines to compute the linear regression rate was not met.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.01
Range_Domain_Maximum: 12.34
Attribute:
Attribute_Label: SHAPE_Leng
Attribute_Definition: Length of feature in meter units (UTM zone 18N, WGS 84)
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 31.661
Range_Domain_Maximum: 996.629
Entity_and_Attribute_Overview:
The entity and attribute information provided here describes the tabular data associated with short-term (~20 years) shoreline change rates. Only modern, MHW, lidar-based shorelines are used to calculate short-term rates, therefore the proxy-datum bias does not apply. Please review the individual attribute descriptions for detailed information. All calculations for length are in meter units and were based on the UTM zone 18N WGS 84 projection. This region has two shapefiles describing rates, long-term (up to 168 years) and short-term (~20 years).
Entity_and_Attribute_Detail_Citation: U.S. Geological Survey