beach-dune interaction for dynamic coastal management
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Faculty of Geosciences
Faculty of Geosciences
Beach-dune interaction for dynamic coastal management
Gerben Ruessink
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Faculty of Geosciences
Beach-dune interaction
Urgency:• nature restoration• long-term coastal safety
No sand sharing: (1) loss in geomorphological dynamics(2) loss in biodiversity(3) no vertical growth with sea-level rise
Dune erosion Dune growth
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Faculty of Geosciences
Building with Nature: Sand Engine
5 July 2011 10 January 2012
1 October 2013 1 oktober 20134 May 2015
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Faculty of Geosciences
Building with Nature: Sand Engine
Beach-dune interaction:
• Short gradients (new embryo dunes)
• Foredune growth ~ 15 m3/m/year
• No dune erosion
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Faculty of Geosciences
Building for Nature: NWNKern
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Faculty of Geosciences
Building for Nature: NWNKern
Trenches:V- to U-shape
Construction After 2 years
Foredunescarping
Sedimentationlobes
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Faculty of Geosciences
Combination: HPZ
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Faculty of Geosciences
Questions
• How much sand is actually blown toward the dunes?
• Which factors affect this amount?
• What to expect from dune remobilization?
• Are present-day large-scale measures effective?
• Can nourishments and dune remobilization be combined?
• …
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Faculty of Geosciences
Needs
• Experiments: Learning by doing
• Long-term (years) monitoring with high resolution (seasons)
• Close co-operation between stakeholders and scientists
• Models with different complexity
• …
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Faculty of Geosciences
Beach-dune interaction: models
Keysers et al. (2014)Plos ONE
Poseidon Aeolus
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Faculty of Geosciences
My projectBeach-dune interaction: models
Need
Accurate predictive
model of aeolian sand
supply
Challenges
Supply limitation
1. How wet?
2. When?
3. How much?
4. Upscaling
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Faculty of Geosciences
Timing of aeolian events
Potential transport
• Events (4 hrs > 8 m/s)
• Hsu (1974)
Observed transport
• Sand-strip activity
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Faculty of Geosciences
Timing of aeolian events
Mismatch between potential and actual events:
• Moderate wind speeds: considerable aeolian activity
• Large speeds are large: no aeolian activity
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Faculty of Geosciences
Considerable aeolian activity under moderate, shore-oblique/parallel winds
Timing of aeolian events
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Faculty of Geosciences
Timing of aeolian events
No aeolian activity under strong shore-normal / oblique winds because of surge
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Faculty of Geosciences
Summary
• From preventing dune-erosion to beach-dune interaction
• Building with and for Nature
• Practice-inspired questions and scientific ideas
• Pilot experiments: ‘Learning by doing’ with long-term
monitoring to eventually predictively understand
Only then ready for the challenges of the decades to come
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Faculty of Geosciences
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Faculty of Geosciences
Surface moisture content
saturated
Reflection (dB)
Mo
istu
re c
on
ten
t (%
)
dry
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Faculty of Geosciences
Surface moisture content
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Faculty of Geosciences
Mismatch between potential and actual events:
• Moderate wind speeds: considerable aeolian activity
• Large speeds are large: no aeolian activity
Timing of aeolian events
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Faculty of Geosciences
Transport magnitude
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Faculty of Geosciences
Results (Xaver)
-80 -70 -60 -50 -40 -300
5
10
15
20E
lev
atio
n (
m M
SL
)
-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
Distance (m)
beforeafter
I. Destruction of new foredune and embryo dunes-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
-80 -70 -60 -50 -40 -300
5
10
15
20E
lev
atio
n (
m M
SL
)
Distance (m)-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
Distance (m)
II. Failure of dune front with successive rotational slides
beforeafter
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Faculty of Geosciences
-80 -70 -60 -50 -40 -300
5
10
15
20E
lev
atio
n (
m M
SL
)
-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
Distance (m)
beforeafter storm
recovery
Results (post-Xaver)