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Background Geology and Characteristics
The 15 different beaches involved in this monitoring program are each unique in terms of geology, morphology, development characteristics, and general locations of the beach profiles. Aerial images of the beach and the profile locations are shown at the start of each beach summary. Each section provides a short summary which describes the geology of each beach, including historic erosion rates (if available) and information on the locations of beach profile marks, if surveyed. Many of the beach geology descriptions have been adapted from Heinze (2001). Each beach is subsequently described in terms of generalized annual and seasonal changes.
Annual and Seasonal Beach Profile Changes
The shapes of annual and seasonal beach profiles are heavily dependent upon both long-term and short-term (storm-induced) erosion or accretion. Typically, annualized mean beach profiles remove short-term changes (variance) and provide a more stable longer-term representation of the beach profile shape.
The shapes of seasonal beach profiles are highly dependent on storm-induced episodes of accretion or erosion. For this study, "winter" months have been generalized to include the months November through April. During these months, there are more frequent storm conditions and beach profiles tend to erode dunes and lose sediment, resulting in a flatter profile and a larger deposit of sand offshore within a sandbar. Conversely, during summer months (characterized as May through October for this study) when wave conditions are generally calmer, beaches tend to build, or prograde, and beach profiles react by having more sediment on higher portions of the profile, resulting in a wider berm and better developed dunes.
To analyze annual beach changes (at each beach profile location) an annual mean beach profile was calculated for each year that data were available. The methodology used to create these profiles was as follows:
In order to quantify seasonal changes, all collected profiles from all available years were grouped into the two different seasons: summer (May to October) and winter (November to April). For each season, a mean profile was calculated using the same methodology discussed above. Additionally, the maximum and minimum profile envelopes - shown as dashed lines - were calculated to show the maximum and minimum recorded variations around the mean profile shape. Also, plots showing the standard deviation - the variance around the mean values - were created and plotted against the standardized X-axis. This was done so that vertical seasonal variations of certain features, such as a sand dune or berm, could be quantitatively described.
This section will provide a qualitative summary description of the annual mean profile changes observed, along with the seasonal changes and characteristics deduced at each of the profile locations at each beach, for which data were available.
Last updated on January 3, 2008
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