research >coastal change >monitoring >clammer

site map

Beach Morphology Monitoring Program

Individual point measurements are densely spaced in the alongshore direction (data points are collected every 5 - 10 m, 16 - 32 ft) to resolve relatively small-scale features such as beach cusps, and are over long enough distances to resolve larger scale, potentially migrating features such as mega-cusps, rip-current embayments, and sand waves. Several surface maps are collected in each sub-cell to resolve regional gradients in beach change. The cross-shore distance between alongshore transects is typically 20 - 30 m (65 - 100 feet) but is determined in the field based on cross-shore breaks in beach slope such as at crests and troughs of swash bars and sand berms.  The non-uniformly spaced raw data (typically 5,000 to 10,000 points) are mapped onto a uniform 2-dimensional gridded surface via triangle-based, weighted linear interpolation, allowing for comparison with subsequent data sets. Although individual grid elevations feature sub-decimeter accuracy, the root mean squared (RMS) error of the interpolated beach surface compared to detailed beach profile surveying using a leveled fixed-height pole is typically 5 cm.

3-D Surface Map

The figure to the left illustrates a sample three-dimensional surface map at Ocean Shores, WA (km 120 - 124) as measured by the CLAMMER on 18 August 1997.  The surface map is vertically and horizontally exaggerated to emphasize the very distinct mega-cusp/rip-current embayment field that is often present at this site and to account for the variation in length and width of the survey site.  The beach surface is approximately 200 m wide while the survey extends nearly 4 km in the alongshore direction.

Elevation Contours

Once the CLAMMER data are gridded onto a surface, contour lines can be extracted.  The figure to the right shows the 1.0-m, 2.0-m, and 3.0-m contours for the same survey at Ocean Shores.  The plot includes the location of the wave bumpers (a tiered, rock revetment) and the location of the Grays Harbor North Jetty.  One way to visualize the observed coastal change patterns is through plotting the migration of contour lines.

Contour Change

The figure to the left reveals the changes in the 2.0-m contour line position that occurred between the summer 1997 Ocean Shores surface map and the winter 1998 surface map.  Within 100 meters (330 feet) of the Grays Harbor North Jetty, the 2.0-m contour migrated seaward approximately 30 m (100 feet).  The remainder of the 4-km (2.5 mile) survey area has substantial variability associated with the mega-cusp and rip current embayment fields evident during both the summer and winter surveys.  However, a net recession of approximately 25 m (80 feet)  is the average contour (shoreline) change over the 4.0-km (2.5-mile) reach.

Follow these links for more information on how the monitoring program employs GPS equipment or to view a map of the monitoring program sampling locations.

Ecology - SEA Program | USGS - Coastal & Marine Geology

This is
Maintained by CMAP, Washington Department of Ecology
Address questions and comments to George Kaminsky
Modified 22 Mar 2012