Multi-year evolution of a nourished beach
preliminary results
Kathelijne WijnbergStefan Aarninkhof
Objective
• Monitor a nourished beach with Argus video remote sensing technology in terms of one or more CSI’s defined in the Coastview project
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
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)
Mon
thly
In
tert
idal
Bath
ym
etr
ies
(aft
er:
Caljou
w /
Nip
ius)
Egmond station‘Jan van Speyk’
June 1999-
August 2001
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)
The dataMean : 60 m 60 m 0 m
St.dev. : 29 m 12 m 26 m
Variance : 844 m2 149 m2 (18%) 695 m2 (82%)
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%)
nourishment
Recon
str
ucte
d M
TL d
ata
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
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.
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