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Regional Bathymetric Change

Sixteen digital bathymetric data sets were used to develop seafloor models (grids) for two time periods, 1926 and 1998.  These regional data sets were constructed to serve as the bottom condition for wave modeling experiments.  The grids cover approximately 7 million km2 between Tillamook Head, OR and Point Grenville, WA.  Original hydrographic sounding data were acquired from two sources: NOAA-National Ocean Service (formerly U.S. Coast and Geodetic Survey) and the U.S. Army Corps of Engineers. 

The historic data set (1926) was generated using survey information collected between 1926 and 1974, although the majority of the data were collected between 1926 and 1930.  These represent the most recent hydrographic surveys available on a region-wide scale off the Washington - Oregon coast.  The modern data set (1998) includes data from hydrographic surveys collected around the estuaries of the Columbia River littoral cell (Grays Harbor, Willapa Bay, and Columbia River).

A comparison of the two time periods revealed the following results:

  • Columbia River: The contours of the historic data at the southern boundary are skewed offshore relative to the modern data suggesting dramatic steepening of the shoreface and nearshore between 1926 and 1998.

  • Willapa Bay: The position of the Willapa Bay ebb-tidal delta migrated about 4.5-km northwest between 1926 and 1998.  Unfortunately the modern (1998) data set did not included neither the northern nor seaward extent of the ebb-tidal delta, and as a result modification of the data set was required to generate a reasonable ebb-tidal delta surface for the modern period.

  • Grays Harbor: The northern portion of the historic data is offset shoreward relative to the modern data set suggesting shoaling and deposition of material on the shoreface between 1926 and 1998.

 A complete discussion of the techniques used to compile, edit and process the data is offered in the U.S. Geological Survey Open File Report 00-448 Non-navigational gridded bathymetry data: Washington - Oregon coast: 1926 - 1998 (3.9 MB).


The following Adobe Acrobat files provide additional details about regional bathymetric change data.  The Adobe Acrobat Reader is necessary to view these files.

A complete list of Southwest Washington Coastal Erosion Study publications is also available.

 

Ecology - SEA Program | USGS - Coastal & Marine Geology

This is http://www.ecy.wa.gov/programs/sea/swces/research/change/bathy_change.htm
Maintained by CMAP, Washington Department of Ecology
Address questions and comments to George Kaminsky
Modified 22 Mar 2012