15. Contents of the Descriptive File

The following is a listing of the general descriptive information file (ndp043c.txt) distributed by CDIAC as part of this NDP. This file provides variable descriptions, formats, units, and other pertinent information about each file associated with this coastal hazards data base.

Title of the Data Base

A Coastal Hazards Data Base for the U.S. West Coast

Contributors

Vivien M. Gornitz
Center for Climate Systems Research, Columbia University
Goddard Institute for Space Studies, National Aeronautics and Space Administration
New York, New York

Tammy W. Beaty
Carbon Dioxide Information Analysis Center, Environmental Sciences Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee

Richard C. Daniels
Energy, Environment and Resources Center, The University of Tennessee
Knoxville, Tennessee
Current affiliation:
Shorelands and Water Resources Program, Water Division, Department of Ecology
Olympia, Washington

Scope of the Data

The 29 data variables within A Coastal Hazards Data Base for the U.S. West Coast, and the corresponding coastal vulnerability indices that may be derived from algorithms listed within this NDP, may be used by coastal planning, research, and management agencies to identify shorelines at risk from coastal erosion and inundation. This data base should be used to identify areas where further study is necessary. In addition, these data may be used in combination with appropriate climatological data (e.g., Birdwell and Daniels 1991) to identify coastal areas that are vulnerable to coastal erosion and inundation from sea-level rise or storm surge (e.g., Gornitz et al. 1994).

This data base consists of the following data sets: elevation, bedrock geology, geomorphology, sea-level trends, horizontal shoreline movements (erosion/accretion), tidal ranges, and wave heights. For several of these data sets, minimum, mean, and maximum data values are available. These data variables may be divided into two basic classes, one that measures erosion potential and one that is related to inundation risk. The erosion risk of each coastal grid cell or line segment may be determined based on geology, geomorphology, shoreline displacement, tidal ranges and wave heights, while the inundation risk may be estimated based on sea-level trends and elevations.

Seven of the 29 data variables are classified versions of other variables within this data base. The seven classified risk variables contain "risk values" of one to five for each coastal grid cell and line segment in this data base. These risk variables may be used to calculate a coastal vulnerability index (CVI) to identify areas on the West Coast that are vulnerable to sea-level rise or coastal erosion.

Data Formats

This data base has been divided into five data groups. Each of these five data groups is provided in two different data formats. The first format is designed for use by the ARC/INFO Geographic Information System (GIS). This format stores the data as polygons (e.g., WCGRID and WCRISK), arcs (e.g., WCLINE and WCOAST), or as points (e.g., WCPOINT). The second format contains comparable data that have been converted into flat ASCII data files for use by raster GISs or non-GIS data base systems.

The first two data groups are registered to a 0.25° latitude by 0.25° longitude grid. The first, WCGRID (Files 4 and 5) provides the 22 original data variables, while the second data group, WCRISK (Files 8 and 9) provides the seven relative risk variables.

The third data group is registered to line segments derived from a 1:2,000,000 digitized U.S. West Coast coastline. WCLINE (Files 12 and 13) provides 29 data variables (i.e., the 22 original and the seven relative risk data variables).

The fourth data group, WCPOINT (Files 16 and 17), provides the source information used in the development of the tidal-range and sea-level trends data sets. Data variables included in this data group are station names/numbers, record lengths, and longitude/latitude locations of the actual data point. These data represent the physical location of the occurring data point, and will allow the precise location of each station used in calculating the gridded tidal-range and sea-level-rise data variables within the 0.25° grid cells of data groups WCGRID and WCRISK to be identified.

Finally, the last group contains a 1:2,000,000 digitized coastline of the U.S. West Coast, WCOAST (files 20 and 21). These line segments are identical to those found in data group WCLINE; however, no data values are provided with this data group.

A description of the contents of each of the data groups and files included with this data base follows:

  1. WCGRID: Gridded polygon data for the 22 original data variables. Data sets contained in this group include elevation, geology, geomorphology, sea-level trend, shoreline displacement (erosion/accretion), tide range, and wave heights.

  2. WCRISK: Gridded polygon data for the seven classified risk variables. The risk variables are classified versions of the following original variables: mean coastal elevation, geology, geomorphology, local subsidence trend, mean shoreline displacement, mean tidal range, and maximum significant wave height.

  3. WCLINE: 1:2,000,000 digitized line segment data for the U.S. West Coast containing the 29 data variables (i.e., the 22 original data variables and the seven classified risk variables).

  4. WCPOINT: Point data for the stations used in calculating the sea-level trend and tide-range data sets. Data include station names/numbers, record length, latitude/longitude location, and mean and maximum data values (when available).

  5. WCOAST: 1:2,000,000 digitized coastline of the U.S. West Coast. The coastline was extracted from a digitized map of the United States compiled by the U.S. Geological Survey.

To improve the portability of the information in the data files, FORTRAN and SAS input/output routines have been included with this data base for each of the flat ASCII data files. These input/output routines are intended to be used to read/write the data values contained in the flat ASCII data files [containing the gridded data base, the original point data (for the sea-level trend and tide-range variables), and the digitized U.S. West coastline].

The data groups in this data base are available as exported ARC/INFO coverages (Version 7). The export files must be read into an ARC/INFO GIS using the IMPORT command with the COVER option after uploading the files onto a computer. These files are in a GEOGRAPHIC projection, which means the coverages are projected in a spherical reference grid using latitude and longitude coordinates that are stored in decimal degrees (DD). The flat ASCII files contain an identical version of this data base.

The gridding method used in this data base consists of 0.25° latitude by 0.25° longitude grid cells. These cells cover the area defined by the following coordinates: 126°W, 32°N; 126°W, 49°N; 116°W, 49°N; and 116°W, 32°N. The origin of the grid is at 126°W, 32°N, and grid identifiers increase from left to right, bottom to top. The data contained within each grid cell is an average for the entire grid cell. The grid cell identification number is located in the center of each cell and although it is not the physical location of each data value, it represents averages for all data points located within the cell.

The flat ASCII versions of the files have been provided to allow use of these data by users who do not have access to ARC/INFO software. The format and contents of each of the flat ASCII files are described in the following section (the ARC/INFO coverages have the same variables and general format as described herein for the ASCII files).

Data Group WCGRID:

This data group contains gridded data for the 22 original data variables. These data variables are from the seven data sets and are as follows: mean, maximum, and minimum elevation, and the number of 5 grid cells used in deriving the data values; geology; geomorphology; relative sea-level trend, long-term geologic trend (included for compatibility within this series of NDPs), corrected sea-level trend, local subsidence trend, and the years of record of the gauge stations used in calculating these values; mean, maximum, and minimum shoreline displacement, and the number of 3´, 7´.5´, or 15´ grid cells used in deriving the data values; mean and maximum tidal range, mean tide level, and the number of tidal stations used in calculating these values; 20-year mean wave height, maximum significant wave height, and the 20-year mean wave height standard deviation.

The names of the ARC/INFO coverage and flat ASCII files providing these data are WCGRID.E00 (File 4) and WCGRID.ASC (File 5), respectively. File 5 is formatted as follows:

  10 READ(5,100,END=999) ID,ELAVG,ELMAX,ELMIN,ELNUM,
     1 GL,GM,SLR,SLG,SLC,SLS,SLYR
      READ(5,110) ERAVG,ERMAX,ERMIN,ERNUM,TRAVG,
     1 TRMAX,TRLVL,TRNUM,WHAVG,WHMAX,WHSD
100 FORMAT(I5,3F8.2,3I4,4F8.2,I4)
110 FORMAT(3F8.2,I4,3F8.2,I4,3F8.2)

The variables in data group WCGRID (File 5) are shown in Table 9 and are listed as they appear in the file.

Within WCGRID missing data values are identified as follows:

-9999.99 -- A grid cell with real data values that is missing data for a given data variable.

9999 -- A grid cell with integer data values that is missing data for a given data variable.

A value of 0.0 is a valid value for all variables. For the elevation variables 0.0 m indicates that land occurs within the given grid cell, but the mean elevation of this land is < 1.0 m. If the data variables in a given data set, such as elevation, contain data and the "number" variable is set to zero (i.e., ELNUM, ERNUM, TRNUM, or SLYR), then the data variables for the given 0.25° grid cell have been estimated.

Data Group WCRISK:

This data group contains gridded data for the seven classified risk variables. These risk variables are classified versions of the following original variables: mean coastal elevation, geology, geomorphology, local subsidence trend, mean shoreline displacement, mean tidal range, and maximum significant wave height.

The names of the ARC/INFO coverage and flat ASCII files are WCRISK.E00 (File 8) and WCRISK.ASC (File 9), respectively. A summary of the format used in File 9 follows:

  10 READ(5,100,END=999) ID, ELR, GLR, GMR, LSR,
     1 TRR,WHR
100 FORMAT(I5,7I4)

The variables in data group WCRISK, listed in Table 10, are shown as they appear in File 9. A value of zero is used to identify missing data values within the grid cell for the risk variables. If several "no data" values occur within the same grid cell, then any calculated coastal vulnerability index that uses these relative risk factors may not accurately represent the risk of the given coastal area to sea-level rise or coastal erosion (unless some type of corrective action is taken). Grid cells that are not in the coastal zone, or are totally ocean bound, have values of zero for all seven derived risk variables.

Data Group WCLINE:

This data group contains digitized line segments obtained at a scale of 1:2,000,000. The coastline is composed of 1,262 line segments with lengths of 93 m to 88.7 km, with an average length of 5.8 km. Each of these line segments have 29 data variables (attributes) assigned to them (i.e., the 22 original and the seven relative risk data variables). Several of these variables have been directly transferred from WCGRID using the IDENTITY procedure in ARC/INFO. As such, line segment lengths do not indicate the resolution of the data.

These 29 data variables are as follows: mean, maximum, and minimum elevation, the number of 5 grid cells used in deriving the data values, and the elevation risk (i.e., the classified version of the mean elevation variable); geology and the geology risk (i.e., the classified version of the geology variable; geomorphology and geomorphology risk (i.e., the classified version of the geomorphology variable); relative sea-level trend, global-trend, corrected sea-level trend, local subsidence trend, the years of record of the gauge stations used in calculating these values, and the local subsidence trend risk (i.e., the classified version of the local subsidence trend variable); mean, maximum, and minimum shoreline displacement, the number of 3´, 7.5´, or 15´ grid cells used in deriving the data values, and erosion risk (i.e., the classified version of the mean erosion/accretion variable); mean and maximum tidal range, mean tide level, the number of tidal stations used in calculating these values, and the tidal-range risk (i.e., the classified version of the mean tidal range); 20-year mean wave height, maximum significant wave height, the 20-year mean wave height standard deviation, and the wave-height risk (i.e., classified version of the maximum significant wave-height variable).

The names of the ARC/INFO coverage and flat ASCII file that provide these data variables are WCLINE.E00 (File 12) and WCLINE.ASC (File 13), respectively. File 13 is formatted as follows:

 10 READ(5,100,END=999) ID,ELAVG,ELMAX,ELMIN,ELNUM,
    1 ELR,GL,GLR,GM,GMR,SLR,SLG,SLC
      READ(5,110) SLS,SLYR,LSR,ERAVG,ERMAX,ERMIN,
    1 ERNUM,ERR,TRAVG,TRMAX,TRLVL,TRNUM,TRR
      READ(5,120) WHAVG,WHMAX, WHSD,WHR
100 FORMAT(I5,3F8.2,6I4,3F8.2)
110 FORMAT(2I4,3F8.2,2I4)
120 FORMAT(3F8.2,I4)

The variables in data group WCLINE (File 13) are shown in Table 11 and are listed as they appear in the file. Within WCLINE, missing data values are indicated as follows:

-9999.99-- A line segment with real data values that is missing data for a given data variable.

9999-- A line segment with integer data values that is missing data for a given data variable.

0-- A line segment with missing data values for the risk variables (i.e., for variables ELR,

ERR, WHR, TRR, LSR, GLR, GMR only).

A value of 0.0 is a valid value for all but the risk variables. For the elevation variables 0.0 m indicates that land occurs within the given grid cell, but the maximum elevation of this land is < 1.0 m. If the data variables in a given data set, such as elevation, contain data and the "number" variable is set to zero (i.e., ELNUM, ERNUM, TRNUM, or SLYR), then the data variables for the given 0.25° grid cell have been estimated.

Data Group WCPOINT:

This data group contains the point data for the stations used in calculating the relative sea-level trend, long-term geologic-trend, corrected sea-level trend, local subsidence trend, mean tide range, maximum tide range, and mean tide level variables contained within data group WCGRID. Data include station names, station number, record length, latitude/longitude location, and data variable values.

The names of the ARC/INFO coverage and flat ASCII file are WCPOINT.E00 (File 16 and WCPOINT.ASC (File 17), respectively. A summary of the format used for File 17 follows:

 10 READ(5,100,END=999) ID,SLLONG,SLLAT,SLR,SLG,
    1 SLC,SLS,SLYR
      READ(5,110) SLNAME,TRLONG,TRLAT,TRAVG,
    1 TRMAX,TRLVL
      READ(5,120) TRID,TRNAME
100 FORMAT(I5,6F8.2,I4)
110 FORMAT(A40,5F8.2)
120 FORMAT(I5,A45)

The variables listed in Table 12 are listed as they appear in data group WCPOINT (File 17). Within this data file, WCPOINT, missing data values are indicated with one of the following values:

0.0 or 0 - A sea-level or tide-range station that has not been assigned data values. This data group includes the calculated relative sea-level trend measurements in mm/yr for 16 tide-gauge stations (Woodworth 1995; Spencer and Woodworth 1993) and the tide table data for 410 NOAA stations (NOS 1992). The sea-level and tide-range stations each have unique data variables. When the 16 stations used for the calculated sea-level trend measurements are present, the tide range variables are 0.0 or 0. When the 410 NOAA stations are present, the sea-level variables are 0.0 or 0.

Data Group WCOAST:

The final data group, WCOAST (Files 20 and 21), contains a 1:2,000,000 digitized coastline of the U.S. West Coast made up of 1,262 line segments. Data in this coverage were extracted from a digitized map of the United States (originally compiled by the U.S. Geological Survey). This coastline may be overlaid onto any of the data groups previously discussed to provide locational information when plotting the data variables. The line segment identification numbers used herein are identical to the line segment identification numbers used in WCLINE.ASC. Unlike the other data groups within this data base this coverage contains no attribute values. However, such overlay commands as UNION, INTERSECT, and IDENTITY in ARC/INFO (or other GISs) may be used to transfer the gridded data values to the coastal segments, thus simplifying the interpretation of any derived indices.

The name of the ARC/INFO coverage where the coastline resides is WCOAST.E00 (File 20), and the flat ASCII data file with this same information is in WCOAST.ASC (File 21). Since this file is line based, the data values in WCOAST.ASC contain the line segment name, the number of points in the line, and a listing of the points that describe each line, for all 1,262 line segments that define the West Coast.

The flat ASCII version of this file contains a listing of the line segments (or arcs) that describe the coast in the BNA format. An example of the format for this file is shown in Table 13.