Multiyear evolution of a nourished beach preliminary results Kathelijne Wijnberg Stefan Aarninkhof

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Multi-year evolution of a nourished
beachpreliminary results Kathelijne
WijnbergStefan Aarninkhof
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Objective

• Monitor a nourished beach with Argus video remote
  sensing technology in terms of one or more CSIs
  defined in the Coastview project

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Study area

• Egmond (NL), Argus site Jan van Speijk
  lighthouse
• Beach nourishment
• June 30 July 5, 2000
• location y 0 800 m
• volume 0.2x106 m3

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Data set

• Data set 43 monthly intertidal bathymetries
  (IBMapper)
• t range Jun. 1999 to Dec. 2002
• y range -680 m to 680 m
• z range 0/-0.4 m NAP to 0.9 m NAP
• ?
• 0.2 m NAP contour (Mean Tide Level)

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Monthly Intertidal Bathymetries(after Caljouw /
Nipius)
Egmond station Jan van Speyk June
1999 - August 2001
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Approach to data analysis

• Temporal evolution of alongshore-averaged MTL
  position
• Temporal evolution of spatial patterns in MTL
  position
• set of spatial patterns empirically defined by
  EOF method (empirical eigenfunctions)

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The data

• Mean 60 m 60 m 0 m
• St.dev. 29 m 12 m 26 m
• Variance 844 m2 149 m2 (18) 695 m2 (82)

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Results EOF analysis

• Explained variance
• 1 84.3 (84.3)
• 2 4.9 (89.2)
• 3 3.3 (92.4)
• 4 2.3 (94.7)

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Reconstructed MTL data
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Conclusions

• At Egmond beach
• Position of the shoreline (MTL) largely (82)
  determined by positioning and amplitude of
  naturally occurring spatial patterns, rather than
  cross-shore movement of the beach as a whole
• Beach nourishment incorporated in dominant
  spatial pattern (explaining 84 of spatial
  pattern variance) within 4 months

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Future work

• Expand analysis to beach width and/or volumes
• Analyse morphological evolution in relation to
  hydrodynamic conditions (H, T, wave direction,
  water level), for prediction purposes.