Coastal Erosion Responses for Alaska - the National Sea Grant ...

46 Richmond—Understanding Shoreline Change
5
Cowell Beach
4
3
2
Elevation (m)
1
0
-1
50 100 150 200 250 300
-2
-3
-4
-5
Distance (m)
10/15/97
11/21/97
12/17/97
1/28/98
2/4/98
2/9/98
2/26/98
4/4/98
4/26/98
6/4/98
7/9/98
8/5/98
10/26/98
Figure 2. Cross-shore profiles from Cowell Beach, Santa Cruz, California, showing the seasonal
erosion and accretion trends during 1997-98 El Niño event. Minimum beach
width occurred in February and is coincident with the maximum storm waves.
The net result was little change over the course of a year.
Monitoring shoreline changes
The most common and widespread method of monitoring shoreline change
is repeated profiling of the foreshore in an effort to capture seasonal and longterm
changes in shoreline position. Methodology varies from traditional
shore-normal survey lines to 3-dimensional survey arrays that incorporate
land-based and offshore survey techniques. Generally, a yearlong record of
repeated surveys is needed to identify gross seasonal changes. Multiyear monitoring
is needed to track longer-term changes. The time between successive
surveys can range from days to months and is determined by desired outcomes
of the study. High rates of coastal change typically require more frequent surveys,
whereas slow-changing coasts need fewer surveys to capture the rate
of change. Figure 2 is an example of shore-normal beach profiles taken to
document beach erosion and recovery during the 1997-98 El Niño in central
California.